Sugar

SUGAR, in chemistry, the generic name for a certain series of carbohydrates, i.e. substances of the general formula Cn(H20)m. Formerly the name was given to compounds having a sweet taste, e.g. sugar of lead, but it is now restricted to certain oxyaldehydes and oxy-ketones, which occur in the vegetable and animal kingdoms either free or in combination as glucosides (q.v.) and to artificial preparations of similar chemical structure. Cane sugar has been known for many centuries; milk sugar was obtained by Fabrizio Bartoletti in 1615; and in the middle of the 18th century Marggraf found that the sugars yielded by the beet, carrot and other roots were identical with cane sugar. The sugars obtained from honey were investigated by Lowitz and Proust, and the latter decided on three species: (I) cane sugar, (2) grape sugar, and (3) fruit sugar; the first has the formula C12H2201,, the others C 6 H 12 0 6. This list has been considerably developed by the discovery of natural as well as of synthetic sugars.

It is convenient to divide the sugars into two main groups: monosaccharoses (formerly glucoses) and disaccharoses (formerly saccharoses). The first term includes simple sugars containing two to nine atoms of carbon, which are known severally as bioses, trioses, tetroses, pentoses, hexoses, &c.; whilst those of the second group have the formula C12H22011 and are characterized by yielding two monosaccharose molecules on hydrolysis. In addition trisaccharoses are known of the formula C13H32016; these on hydrolysis yield one molecule of a monosaccharose and one of a disaccharose, or three of a monosaccharose. It is found also that some monosaccharoses behave as aldehydes whilst others contain a keto group; those having the first character are called aldoses, and the others ketoses. All sugars are colourless solids or syrups, which char on strong heating; they are soluble in water, forming sweet solutions but difficultly soluble in alcohol. Their solutions are optically active, i.e. they rotate the plane of polarized light; the amount of the rotation being dependent upon the concentration, temperature, and, in some cases, on the age of the solution (cf. GLucosE). The rotation serves for the estimation of sugar solutions (saccharimetry). They are neutral to litmus and do not combine with dilute acids or bases; strong bases, such as lime and baryta, yield saccharates, whilst, under certain conditions, acids and acid anhydrides may yield esters. Sugars are also liable to fermentation.' Our knowledge of the chemical structure of the monosaccharoses may be regarded as dating from 1880, when Zincke suspected some to be ketone alcohols, for it was known that glucose and fructose, for example, yielded penta-acetates, and on reduction gave hexahydric alcohols, which, when reduced by hydriodic acid, gave normal and secondary hexyliodide. The facts suggested that the six carbon atoms formed a chain, and that a hydroxy group was attached to five of them, for it is very rare for two hydroxy groups to be attached to the same carbon atom. The remaining oxygen atom is aldehydic or ketonic, for the sugars combine with hydrocyanic acid, hydroxylamine and phenylhydrazine. The correctness of this view was settled by Kiliani in 1885. He prepared the cyanhydrins of glucose and fructose, hydrolysed them to the corresponding oxy-acids, from which the hydroxy groups were split out by reduction; it was found that glucose yielded normal heptylic acid and fructose methylbutylacetic acid; hence glucose is an aldehyde alcohol, CH 2 OH (CH OH) 4 CHO, whilst fructose is a ketone alcohol CH 2 OH (CH OH) 3 CO. CH 2 OH. 2 Kiliani also showed that arabinose, C 6 11 12 0 61 a sugar found in cherry gum, was an aldopentose, and thus indicated an extension of the idea of a " sugar." Before proceeding to the actual synthesis of the sugars, it is advisable to discuss their decompositions and transformations.

I. Cyanhydrins. - The cyanhydrins on hydrolysis give monocarboxylic acids, which yield lactones; these compounds when reduced by sodium amalgam in sulphuric acid solution yield a sugar containing one more carbon atom. This permits the formation of a higher from a lower sugar (E. Fischer) CH20H CH20H / CH CH OH (CH OH) 2 -> (CH OH)2 CH-OH CH OH CO CHO -> Lactone -> Hexose.

Table of contents

1 2. Oximes 2 l - glucose 3 Trioses 4 Tetroses 5 Pentoses 6 Hexoses 7 Configuration of the Hexaldoses. l 8 Maple Sugar 9 Palm Sugar 10 Sorghum Sugar 11 Cane Sugar Manufacture 12 Extraction of Juice 13 Purification 14 Concentration and Crystallization 15 Curing or Preparation of Crystals for the Market 16 Recent Progress 17 Beetroot Sugar Manufacture 18 Slicing 19 Diffusion 20 Saturation 21 Evaporation and Crystallization 22 Curing 23 Carbonatation 24 Refining 25 Melting Pans 26 Filters 27 Retorts for Reburning Char 28 Vacuum Pans and Receivers 29 History and Statistics

2. Oximes

The oximes permit the reverse change, i.e. the passage from a higher to a lower sugar. Wohl forms the oxime and converts it into an acetylated nitrile by means of acetic anhydride and sodium acetate; ammoniacal silver nitrate solution removes hydrocyanic acid and the resulting acetate is hydrolysed by acting with ammonia to form an amide, which is finally decomposed with sulphuric acid.

CH 2 OH CH20H CH20H CH20H (CH OH) 3 -> 01 OH) 3 -> (CH OH) 3 --> (CH OH)3 CH OH CH OH CH OH CHO CHO CH:NOH CN Hexose -p Oxime -> Nitrile -> Pentose.

Ruff effects the same change by oxidizing the sugar to the oxy-acid, ' See Fermentation; and for the relation of this property to structure see Stereoisomerism.

These formulae, however, require modification in accordance with the views of Lowry and E. F. Armstrong, which postulate a y oxidic structure (see Glucose). This, however, does not disturb the tenor of the following arguments.

and then further oxidizing this with Fenton's reagent, i.e. hydrogen peroxide and a trace of a ferrous salt: C 4 H 9 O 4 (CH OH) CHO-->C 4 H 9 O 4 (CH OH) C02H->C4H904 CHO Hexose -> Acid -* Pentose.

3. Phenylhydrazine Derivatives. - Fischer found that if one molecule of phenylhydrazine acted upon one molecule of an aldose or ketose a hydrazone resulted which in most cases was very soluble in water, but if three molecules of the hydrazine reacted (one of which is reduced to ammonia and aniline) insoluble crystalline substances resulted, termed osazones, which readily characterized the sugar from which it was obtained.

R R R CH OH --o CH OH -> C:N NHPh CHO CH :N NHPh. CH :N NHPh.

Aldose R CO CH20H Ketose

0 Hydrazone R -> C:N NHPh. CI-120H -> Hydrazone

-> Osazone; R -> C:N NHPh CH :N NHPh. -? Osazone.

On warming the osazone with hydrochloric acid the phenylhydrazine residues are removed and an osone results, which on reduction with zinc and acetic acid gives a ketose.

R R R C:N NHPh. -> CO y CO CH :N NHPh. CHO CH20H Osazone o Osone -> Ketose.

A ketose may also be obtained by reducing the osazone with zinc and acetic to an osamine, which with nitrous acid gives the ketose: R R R C :N NHPh. -> CO > CO CH :N NHPh. CH2NH2 CH20H.

Osazone -> Osamine -> Ketose.

These reactions permit the transformation of an aldose into a ketose; the reverse change can only be brought about by reducing the ketose to an alcohol, and oxidizing this compound to an aldehyde. It is seen that aldoses and ketoses which differ stereochemically in only the two final carbon atoms must yield the same osazone; and since d-mannose, d-glucose, and d-fructose do form the same osazone (d-glucosazone) differences either structural or stereochemical must be placed in the two final carbon atoms.3 It may here be noticed that in the sugars there are asymmetric carbon atoms, and consequently optical isomers are to be expected. Thus glucose, containing four such atoms, can exist in 16 forms; and the realization of many of these isomers by E. Fischer may be regarded as one of the most brilliant achievements in modern chemistry. The general principles of stereochemistry being discussed in Stereoisomerism (q.v.), we proceed to the synthesis of glucose and fructose and then to the derivation of their configurations.

In 1861 Butlerow obtained a sugar-like substance, methylenitan, by digesting trioxymethylene, the solid polymer of formaldehyde, with lime. The work was repeated by 0. Loew, who prepared in 1885 a sweet, unfermentable syrup, which he named formose, C6H120e and, later, by using magnesia instead of lime, he obtained the fermentable methose. Fischer showed that methose was identical with the a-acrose obtained by himself and Tafel in 1887 by decomposing acrolein dibromide with baryta, and subsequently prepared by oxidizing glycerin with bromine in alkaline solution, and treating the product with dilute alkali at o°. Glycerin appears to yield, on mild oxidation, an aldehyde, CH20H CH(OH) CHO, and a ketone, CH 2 OH CO CH 2 OH, and these condense as shown in the equation: CH 2 OH CH (OH) CHO + CH 2 OH [[Coch 2 Oh = Ch20h Ch(Oh) Ch(Oh) Ch(Oh) Co.Ch20h+H20]].

The osazone prepared from a-acrose resembled most closely the glucosazone yielded by glucose, mannose, and fructose, but it was optically inactive; also the ketose which it gave after treatment with hydrochloric acid and reduction of the osone was like ordinary fructose except that it was inactive. It was surmised that a-acrose was a mixture of dextro and laevo fructose, a supposition which was proved correct by an indirect method. The starting point was ordinary(d)mannite (mannitol),C 6 H 14 0 61 a naturally occurring hexahydric alcohol, which only differed from a-acritol, the alcohol obtained by reducing a-acrose, with regard to optical activity. Mannite on oxidation yields an aldose, mannose, C6H12061 which 3 To distinguish the isomerides of opposite optical activity, it is usual to prefix the letters d- and 1-, but these are used only to indicate the genetic relationship, and not the character of the optical activity; ordinary fructose, for example, being represented as d-fructosealthough it exercises a laevorotatory power - because it is derived from d-glucose.

CH20H CH20H CH OH CH OH (CH OH) 2 -> (CH OH)2 CHO CH-OH CN Pentose -> Cyanhydrin on further oxidation gives a mannonic acid, C 5 H 8 (OH) 5 CO 2 H; this acid readily yields a lactone. Also Kiliani found that the lactone derived from the cyanhydrin of natural arabinose (laevo) was identical with the previous lactone except that its rotation was equal and opposite. On mixing the eslactones and reducing (d + l)-mnanitol was obtained, identical with a-acritol. A separation of a-acrose was made by acting with beer yeast, which destroyed the ordinary fructose and left /-fructose which was isolated as its osazone. Also (d +1) mannonic acid can be split into the d and 1 acids by fractional crystallization of the strychnine or brucine salts. The acid yields, on appropriate treatment, d-mannose and d-mannite. Similarly the 1 acid yields the laevo derivatives.

The next step was to prepare glucose. This was effected indirectly. The identity of the formulae and osazones of d-mannose and d-glucose showed that the stereochemical differences were situated at the carbon atom adjacent to the aldehyde group. Fischer applied a method indicated by Pasteur in converting dextro into laevo-tartaric acid; he found that both d-mannonic and d-gluconic acids (the latter is yielded by glucose on oxidation) were mutually convertible by heating with quinoline under pressure at 140°. It was then found that on reducing the lactone of the acid obtained from d-mannonic acid, ordinary glucose resulted.

Fischer's a-acrose therefore led to the synthesis of the dextro and laevo forms Gf mannose, glucose and fructose; and these substances have been connected synthetically with many other sugars by means of his cyanhydrin process, leading to higher sugars, and Wohl and. Ruff's processes, leading to lower sugars. Certain of these relations are here summarized (the starting substance is in italics): l-Glucose f- 1-arabinose --- l-mannose - l-mannoheptose; glucononose fa-gluco-octose F - a-glucoheptose f- d-glucose - 0-glucoheptose - > /-gluco-octose; d-mannose--> d-mannoheptose--> manno-octose--> mannononose; d-glucose --> d-arabinose - i d-erythrose.

l - glucose

? b-arabinose -+ l-erythrose.

Their number is further increased by spatial inversion of the dicarboxylic acids formed on oxidation, followed by reduction; for example: d- and /-glucose yield d-and l-gulose; and also by Lobry de Bruyn and Van Ekenstein's discovery that hexoses are transformed into mixtures of their isomers when treated with alkalis, alkaline earths, lead oxide, &c.

Monosaccharoses. Biose. - The only possible biose is glycollic aldehyde, CHO.CH20H, obtained impure by Fischer from bromacetaldehyde and baryta water, and crystalline by Fenton by heating dihydroxymaleic acid with water to 60°. It polymerizes to a tetrose under the action of sodium hydroxide.

Trioses

The trioses are the aldehyde and ketone mentioned above as oxidation products of glycerin. Glyceric aldehyde, CH 2 OH CH(OH) CHO, was obtained pure by Wohlon oxidizing acrolein acetal, CH 2 CH(OC 2 H 5) 21 and hydrolysing. Although containing an asymmetric carbon atom it has not been resolved. The ketone, dihydroxyacetone, CH 2 OH CO CH 2 OH, was obtained by Piloty by condensing formaldehyde with nitromethane, reducing to a hydroxylamino compound, which is oxidized to the oxime of dihydroxyacetone; the ketone is liberated by oxidation with bromine water: 3H CHO + CH 3 NO 2 -- (CH 2 OH) 3 C NO 2 - (CH 2 OH) 3 C NH OH -- (CH 2 OH) 2 C: NOH - > (CH20H)2CO. The ketone is also obtained when Bertrand's sorbose bacterium acts on glycerol; this medium also acts on other alcohols to yield ketoses; for example: erythrite gives erythrulose, arabite arabinulose, mannitol fructose, &c.

Tetroses

Four active tetroses are possible, and three have been obtained by Ruff and Wohl from the pentoses. Thus Wohl prepared l-threose from l-xylose and l-erythrose from l-arabinose, and Ruff obtained d- and l-erythrose from d- and l-arabonic acids, the oxidation products of d- and l-arabinoses. Impure inactive forms result on the polymerization of glycollic aldehyde and also on the oxidation of erythrite, a tetrahydric alcohol found in some lichens. d-Erythrulose is a ketose of this series.

Pentoses

Eight stereoisomeric pentaldoses are possible, and six are known: d- and l-arabinose, d- and l-xylose, /-ribose, and d-lyxose. Scheibler discovered l-arabinose in 1869, and regarded it as a glucose; in 1887 Kiliani proved it to be a pentose. d-Arabinose is obtained from d-glucose by Wohl's method. l-Xylose was discovered by Koch in 1886; its enantiomorph is prepared from d-gulose by Wohl's method. /-Ribose and d-lyxose are prepared by inversion from l-arabinose and l-xylose; the latter has also been obtained from d-galactose. We may notice that the pentoses differ from other sugars by yielding furfurol when boiled with hydrochloric acid. Rhamnose or isodulcite, a component of certain glucosides, fucose, found combined in seaweeds and chinovose, present as its ethyl ester, chinovite, in varieties of quina-bark, are methyl pentoses. l-Arabinulose obtained from arabite and Bertrand's sorbium bacterium is a ketose.

Hexoses

The hexoses may be regarded as the most important sub-division of the monosaccharoses. The reader is referred to Glucose and Fructose for an account of these substances. The next important aldose is mannose. d-Mannose, first prepared by oxidizing d-mannite, found in plants and manna-ash (Fraxinus ornus), was obtained by Tollens and Gans on hydrolysing cellulose and by Reis from seminine (reserve cellulose), found in certain plant seeds, e.g. vegetable ivory. l-Mannose is obtained from l-mannonic acid. Other forms are: d- and l-gulose, prepared from the lactones of the corresponding gulonic acids, which are obtained from d- and /-glucose by oxidation and inversion; d- and l-idose, obtained by inverting with pyridine d- and l-gulonic acids, and reducing the resulting idionic acids; d- and l-galactose, the first being obtained by hydrolysing milk sugar with dilute sulphuric acid, and the second by fermenting inactive galactose (from the reduction of the lactone of d, l-galactonic acid) with yeast; and d- and l-talose obtained by inverting the galactonic acids by pyridine into d- and l-talonic acids and reduction. Of the ketoses, we notice d-sorbose, found in the berries of mountain-ash, and d-tagatose, obtained by Lobry de Bruyn and van Ekenstein on treating galactose with dilute alkalis, talose and l-sorbose being formed at the same time. The higher sugars call for no special notice.

Configuration of the Hexaldoses. l

The plane projection of molecular structures which differ stereochemically is discussed under Stereoisomerism; in this place it suffices to say that, since the terminal groups of the hexaldose molecule are different and four asymmetric carbon atoms are present, sixteen hexaldoses are possible; and for the hexahydric alcohols which they yield on reduction, and the tetrahydric dicarboxylic acids which they give on oxidation, only ten forms are possible. Employing the notation in which the molecule is represented vertically with the aldehyde group at the bottom, and calling a carbon atom+or - according as the hydrogen atom is to the left or right, the possible configurations are shown in the diagram. The grouping of the forms 5 to Io with II to 16 is designed to show that the pairs 5, II for example become identical when the terminal groups are the same.

				II	1 2	13	14	15	16
				+	+	+	+	+	-
				+	+	+	-	-	+
				+	-	-	+	-	-
+	+	-	-	- -	+ +	- -	- -	- -	_ -
+	-	+	-	+	-	-	+	-	-
+	-	+	-	+	+	+	-	-	+
}	+	-	-	+	+	+	+	+	-
I	2	3	4	5	6	7	8	9	10

We can now proceed to the derivation of the structure of glucose. Since both d-glucose and d-gulose yield the same active (d) saccharic acid on oxidation, the configuration of this and the corresponding /-acid must be sought from among those numbered 5-10 in the above table. Nos. 7 and 8 can be at once ruled out, however, as acids so constituted would be optically inactive and the saccharic acids are active. If the configuration of d-saccharic acid were given by either 6 or To, bearing in mind the relation of mannose to glucose, it would then be necessary to represent d-mannosaccharic acid by either 7 or 8 - as the forms 6 and Io pass into 7 and 8 on changing the sign of a terminal group; but this cannot be done as mannosaccharic acid is optically active. Nos. 6 and 10 must, in consequence, also be ruled out. No. 5, therefore, represents the configuration of one of the saccharic acids, and No. 9 that of the isomeride of equal opposite rotatory power. As there is no means of distinguishing between the configuration of a dextroand laevo-modification, an arbitrary assumption must be made. No. 5 may therefore be assigned to the d- and No. 9 to the /-acid. It then follows that d-mannose is represented by No. 1, and l-mannose by No. 4,as mannose is produced by reversing the sign of the asymmetric system adjoining the terminal COH group.

It remains to distinguish between 5 and I I, 9 and 15 as representing glucose and gulose. To settle this point it is necessary to consider the configuration of the isomeric pentoses - arabinose and xylosefrom which they may be prepared. Arabinose being convertible into /-glucose and xylose into l-gulose, the alternative formulae to be considered are CH 2 (OH) - - - +COH CH 2 (OH) + + - COH.

1 The following account is mainly from H. E. Armstrong's article Chemistry in the 10th edition of this Encyclopaedia; the representation differs from the projection of Meyer and Jacobsen.

If the asymmetric system adjoining the COH group, which is that introduced in synthesizing the hexose from the pentose, be eliminated, the formulae at disposal for the two pentoses are CH 2 (OH) - - - COH CH 2 (OH)+-- COH.

When such compounds are converted into corresponding dibasic acids, CO 2 H.[CH(OH)) 3.00 2 H, the number of asymmetric carbon atoms becomes reduced from three to two, as the central carbon atom is then no longer associated with four, but with only three different radicles. Hence it follows that the " optical " formulae of the acids derived from two pentoses having the configuration given above will be C02H - 0 - C02H CO 2 H + 0 - C02H, and that consequently only one of the acids will be optically active. As a matter of fact, only arabinose gives an active product on oxidation; it is therefore to be supposed that arabinose is the - - - compound, and consequently CH 2 (OH) - - - + COH = /-glucose CH 2 (OH) + - - - COH = l-gulose.

When xylose is combined with hydrocyanic acid and the cyanide is hydrolysed, together with l-gulonic acid, a second isomeric acid, l-idonic acid, is produced, which on reduction yields the hexaldose l-idose. When l-gulonic acid is heated with pyridine, it is converted into l-idonic acid, and vice versa; and d-gulonic acid may in a similar manner be converted into d-idonic acid, from which it is possible to prepare d-idose. It follows from the manner in which l-idose is produced that its configuration is CH 2 (OH) + - - +COH.

The remaining aldohexoses discovered by Fischer are derived from d-galactose from milk-sugar. When oxidized this aldohexose is first converted into the monobasic galactonic acid, and then into dibasic mucic acid; the latter is optically inactive, so that its configuration must be one of those given in the sixth and seventh columns of the table. On reduction it yields an inactive mixture of galactonic acids, some molecules being attacked at one end, as it were, and an equal number of others at the other. On reducing the lactone prepared from the inactive acid an inactive galactose is obtained from which l-galactose may be separated by fermentation. Lastly, when d-galactonic acid is heated with pyridine, it is converted into talonic acid, which is reducible to talose, an isomeride bearing to galactose the same relation that mannose bears to glucose. It can be shown that d-galactose is CH 2 (OH) + - + - COH, and hence d-talose is CH 2 (OH) + - + + COH.

The configurations of the pentaand tetra-aldoses have been determined by similar arguments; and those of the ketoses can be deduced from the aldoses.

Disaccharoses. The disaccharoses have the formula C12H22011 and are characterized by yielding under suitable conditions two molecules of a hexose: C12H22011+H20=C6H1206+C6H1206. The hexoses so obtained are not necessarily identical: thus cane sugar yields d-glucose and d-fructose (invert sugar); milk sugar and melibiose give d-glucose and d-galactose, whilst maltose yields only glucose. Chemically they appear to be ether anhydrides of the hexoses, the union being effected by the aldehyde or alcohol groups, and in consequence they are related to the ethers of glucose and other hexoses, i.e. to the alkyl glucosides. Cane sugar has no reducing power and does not form an hydrazone or osazone; the other varieties, however, reduce Fehling's solution and form hydrazones and osazones, behaving as aldoses, i.e. as containing the group CH(OH) CHO. The relation of the disaccharoses to the aand l3-glucosides was established by E. F. Armstrong (Journ. Chem. Soc., 1903, 85, 1305), who showed that cane sugar and maltose were a-glucosides, and raffinose an a-glucoside of melibiose. These and other considerations have led to the proposal of an alkylen oxide formula for glucose, first proposed by Tollens; this view, which has been mainly developed by Armstrong and Fischer, has attained general acceptance (see Glucose and Glucosjde). Fischer has proposed formulae for the important disaccharoses, and in conjunction with Armstrong devised a method for determining how the molecule was built up, by forming the osone of the sugar and hydrolysing, whereupon the hexosone obtained indicates the aldose part of the molecule. Lactose is thus found to be glucosido-galactose and melibiose a galactosido-glucose.

Several disaccharoses have been synthesized. By acting with hydrochloric acid on glucose Fischer obtained isomaltose, a disaccharose very similar to maltose but differing in being amorphous and unfermentable by yeast. Also Marchlewski (in 1899) synthesized cane sugar from potassium fructosate and acetochloroglucose; and after Fischer discovered that acetochlorohexoses readily resulted from the interaction of the hexose penta-acetates and liquid hydrogen chloride, several others have been obtained.

Cane sugar, saccharose or saccharobiose, is the most important sugar; its manufacture is treated below. When slowly crystallized it forms large monoclinic prisms which are readily soluble in water but difficultly soluble in alcohol. It melts at 160°, and on cooling solidifies to a glassy mass, which on standing gradually becomes opaque and crystalline. When heated to about 200° it yields a brown amorphous substance, named caramel, used in colouring liquors, &c. Concentrated sulphuric acid gives a black carbonaceous mass; boiling nitric acid oxidizes it to d-saccharic, tartaric and oxalic acids; and when heated to 160° with acetic anhydride an octa-acetyl ester is produced. Like glucose it gives saccharates with lime, baryta and strontia.

Milk sugar, lactose, lactobiose, C12H22011, found in the milk of mammals, in the amniotic liquid of cows, and as a pathological secretion, is prepared by evaporating whey and purifying the sugar which separates by crystallization. It forms hard white rhombic prisms (with 1H 2 0), which become anhydrous at 400 and melt with decomposition at 205°. It reduces ammoniacal silver solutions in the cold, and alkaline copper solutions on boiling. Its aqueous solution has a faint sweet taste, and is dextro-rotatory, the rotation of a fresh solution being about twice that of an old one. It is difficultly fermented by yeast, but readily by the lactic acid bacillus. It is oxidized by nitric acid to d-saccharic and mucic acids; and acetic anhydride gives an octa-acetate.

Maltose, malt-sugar, maltobiose, C12H22011, is formed, together with dextrine, by the action of malt diastase on starch, and as an intermediate product in the decomposition of starch by sulphuric acid, and of glycogen by ferments. It forms hard crystalline crusts (with 1H 2 0) made up of hard white needles.

Less important disaccharoses are: Trehalose or mycose, C12H22011.2H20, found in various fungi, e.g. Boletus edulis, in the Oriental Trehala and in ergot of rye; melibiose, C12H22011, formed, with fructose, on hydrolysing the trisaccharose melitose (or raffinose), C18H32016.5H20, which occurs in Australian manna and in the molasses of sugar manufacture; touranose, C12H22011, formed with d-glucose and galactose on hydrolysing another trisaccharose, melizitose, C,8H32016 2H20, which occurs in Pinus larix and in Persian manna; and agavose, C12H22011, found in the stalks of Agave americana. (X.) Sugar Manufacture Sugar-cane is a member of the grass family, known botanically as Saccharum officinarum, the succulent stems of which are the source of cane sugar. It is a tall perennial grass-like plant, giving off numerous erect stems 6 to 12 ft. or more in height from a thick solid jointed root-stock. The stems are solid and marked with numerous shining, polished, yellow, purple or striped joints, 3 in. or less in length, and about II in. thick. They are unbranched and bear in the upper portion numerous long narrow grass-like leaves arranged in two rows; the leaf springs from a large sheath and has a more or less spreading blade 3 ft. in length or longer, and 3 in. or more wide. The small flowers or spikelets are borne in pairs on the ultimate branches of a much branched feathery plume-like terminal grey inflorescence, 2 ft. or more long. Production of flowers is uncertain under cultivation and seed is formed very rarely. The plant is readily propagated by cuttings, a piece of the stem bearing buds at its nodes will root rapidly when placed in sufficiently moist ground. The sugar-cane is widely cultivated in the tropics and some sub-tropical countries, but is not known as a wild plant. Its native country is unknown, but it probably originated in India or some parts of eastern tropical Asia where it has been cultivated from great antiquity and whence its cultivation spread westwards and eastwards. Alphonse de Candolle (Origin of Cultivated Plants, p. 158) points out that the epoch of its introduction into different countries agrees with the idea that its origin was in India, Cochin-China or the Malay Archipelago, and regards it as most probable that its primitive range extended from Bengal to Cochin-China. The sugar-cane was introduced by the Arabs in the middle ages into Egypt, Sicily and the south of Spain where it flourished until the abundance of sugar in the colonies caused its cultivation to be abandoned. Dom Enrique, Infante of Portugal, surnamed the Navigator (1394-1460) transported it about 1420, from Cyprus and Sicily to Madeira, whence it was taken to the Canaries in 1503, and thence to Brazil and Hayti early in the 16th century, whence it spread to Mexico, Cuba, Guadeloupe and Martinique, and later to Bourbon. It was introduced into Barbadoes from Brazil in 1641, and was distributed from there to other West Indian islands. Though cultivated in sub-tropical countries such as Natal and the Southern states of the Union, it is essentially tropical in its requirements and succeeds best in warm damp climates such as Cuba, British Guiana and Hawaii, and in India and Java in the Old World. The numerous cultivated varieties are distinguished mainly by the colour of the internodes, whether yellow, red or purple, or striped, and by the height. of the culm. Apart from the sugar-cane and the beet, which are dealt with in detail below, a brief reference need only be made here to maple sugar, palm sugar and sorghum sugar.

Maple Sugar

This is derived from the sap of the rock or sugar maple (Ater saccharinum), a large tree growing in Canada and the United States.

The sap is collected in spring, just before the foliage develops, and is procured by making a notch or boring a hole in the stem of the tree about 3 ft. from the ground. A tree may yield 3 gallons of juice a day and continue flowing for six weeks; but on an average only about 4 lb of sugar are obtained from each tree, 4 to 6 gallons of sap giving 1 lb of sugar. The sap is purified and concentrated in a simple manner, the whole work being carried on by farmers, who themselves use much of the product for domestic and culinary purposes.

Palm Sugar

That which comes into the European market as jaggery or khaur is obtained from the sap of several palms, the wild date (Phoenix sylvestris), the palmyra (Borassus flabellifer), the coco-nut (Cocos nucifera), the gomuti (Arenga saccharifera) and others. The principal source is Phoenix sylvestris, which is cultivated in a portion of the Ganges valley to the north of Calcutta. The trees are ready to yield sap when five years old; at eight years they are mature, and continue to give an annual supply till they reach thirty years. The collection of the sap (toddy) begins about the end of October and continues, during the cool season, till the middle of February. The sap is drawn off from the upper growing portion of the stem, and altogether an average tree will run in a season 350 lb of toddy, from which about 35 lb of raw sugar - jaggery - is made by simple and rude processes. Jaggery production is entirely in native hands, and the greater part of the amount made is consumed locally; it only occasionally reaches the European market.

Sorghum Sugar

The stem of the Guinea corn or sorghum (Sorghum saccharatum) has long been known in China as a source of sugar. The sorghum is hardier than the sugar-cane; it comes to maturity in a season; and it retains its maximum sugar content a considerable time, giving opportunity for leisurely harvesting. The sugar is obtained by the same method as cane sugar.

Cane Sugar Manufacture

The value of sugar-canes at a given plantation or central factory would at first sight appear to vary directly as the amount of saccharine contained in the juice expressed from them varies, Sugar-canes. and if canes with juice indicating 9° Beaume be made a basis of value or worth, say at ios. per ton, then canes with juice indicating in degrees Beaume to° 9° 8° 7° 6° and containing in sugar.. 18.05%' 1 6.23% 14.42% 12.61% IO. 80% would be worth per ton. .. ii/14 to/- 8/102 7/94 6/8 But this is not an accurate statement of the commercial value of sugar-canes - that is, of their value for the production of sugar to the planter or manufacturer - because a properly equipped and balanced factory, capable of making ioo tons of sugar per day, for ioo days' crop, from canes giving juice of 9° B., or say Io,000 tons of sugar, at an aggregate expenditure for manufacture (i.e. the annual cost of running the factory) of £3 per ton, or f30,000 per annum, will not be able to make as much sugar per day with canes giving juice of 8° B., and will make still less if they yield juice of only 6° B. In practice, the expenses of upkeep for the year and of manufacturing the crop remain the same whether the canes are rich or poor and whether the crop is good or bad, the power of the factory being limited by its power of evaporation. For example, a factory able to evaporate 622 tons of water in 24 hours could treat I 000 tons of canes yielding juice of 9° B., and make therefrom too tons of sugar in that time; but this same factory, if supplied with canes giving juice of 6° B., could not treat more than 935 tons of canes in 24 hours, and would only make therefrom 62.2 tons of sugar.

The following table may be useful to planters and central factory owners. It shows the comparative results of working with juice of the degrees of density mentioned above, under the conditions described, for one day of 24 hours, and the real value, as raw material for manufacture, of cane giving juice of 6° B. to Io° B., with their apparent value based solely on the percentage of sugar in the juice.

The canes in each case are assumed to contain 88% of juice and 12% of fibre, and the extraction by milling to be 75% of the weight of canes - the evaporative power of the factory being equal to 622 tons per 24 hours. The factory expenses are taken at £30,000 per annum, or £3 per ton on a crop of 10,000 tons (the sugar to cost £8 per ton all told at the factory) - equivalent to £300 per day for the loo working days of crop time.

Degrees Beaume.	6°	7°	8°	9°	10°
Tons of canes crushed per day	935' 6	95 6 ' 2	977.4	1000	1023.8
Tons of juice ex- pressed.. .	701.7	7 1 7.2	733.1	750	767.9
Tons of water evaporated	622	622	622	622	622
Tons of 1st Mas- secuite	79.7	95.2	III I	128	145'9
Tons sugar of all classes recovered	. 62.2	74'3	86.7	100	114.0
Total output of sugar in loo days. Tons	6220	7430	8670	10,000	11,400
Total value of all sugars per day
at £8 per ton	£497, 6 /-£594,		4/-£ 6 93, 6/-	£800	£912
Less factory ex- penses per day .	£300	£300	£300	£300	£300
Leaves for canes
crushed.. .	£197, 6 /-£ 2 94,		4/-£393, 6 /-	£5 00	£612
Real value of canes per ton	4/21-	6/2	8/-	10/-	I Oil
Apparent value (see preceding
Table)	6/8	7/94	8/Io	to/-	II/14

But it is obvious that it would not pay a planter to sell canes at 4s. 21d. a ton instead of at ios. a ton, any more than it would pay a factory to make only 62.2 tons of sugar in 24 hours, or 6220 tons in the crop of loo days, instead of 10,000 tons. Hence arises the imperative necessity of good cultivation by the planter, and of circumspection in the purchase and acceptance of canes on the part of the manufacturer.

The details of manufacture of sugar from canes and of sugar from beetroots differ, but there are five operations in the production of the sugar of commerce from either material which are common to both processes. These are: - I. The extraction of the juice.

2. The purification or defecation of the juice.

3. The evaporation of the juice to syrup point.

4. The concentration and crystallization of the syrup.

5. The curing or preparation of the crystals for the market by separating the molasses from them.

Extraction of Juice

The juice is extracted from canes by squeezing them between rollers. In India at the present day there are thousands of small mills worked by hand, through which extraction the peasant cultivators pass their canes two or three at a time, squeezing them a little, and extracting per haps a fourth of their weight in juice, from which they make a substance resembling a dirty sweetmeat rather than sugar. In Barbadoes there are still many estates making good Mascabado sugar; but as the juice is extracted from the canes by windmills, and then concentrated in open kettles heated by direct fire, the financial results are disastrous, since nearly half the yield obtainable from the canes is lost. In the best organized modern cane sugar estates as much as 122% of the weight of the canes treated is obtained in crystal sugar of high polarizing power, although in Louisiana, where cultivation and manufacture are alike most carefully and admirably carried out, the yield in sugar is only about 7% of the weight of the canes, and sometimes, but seldom, as much as 9%. This is due to conditions of climate, which are much less favourable for the formation of saccharine in the canes than in Cuba. The protection afforded to the planters by their government, however, enables them to pursue the industry with considerable profit, notwithstanding the poor return for their labour in saleable produce. As an instance of the influence of climatic conditions combined with high cultivation the cane lands of the Sandwich Islands may be cited. Here the tropical heat is tempered by constant trade winds, there is perfect immunity from hurricanes, the soil is peculiarly suited for cane-growing, and by the use of specially-prepared fertilizers and an ample supply of water at command for irrigation the land yields from 50 to 90 tons of canes per acre, from which from 12 to 14% of sugar is produced. To secure this marvellous return, with an annual rainfall of 26 in., as much as 52,000,000 gallons of water are pumped per 24 hours from artesian wells on one estate alone. With an inexhaustible supply of irrigation water obtainable, there is no reason why the lands in Upper Egypt, if scientifically cultivated and managed, should not yield as abundantly as those in the Sandwich Islands.

In the Paris Exhibition of 1900 a cane-crushing mill was shown with three rollers 32 in. in diameter by 60 in. long. It is driven by a powerful engine through triple gearing of 42 to 1, and speeded to have a surface velocity of rollers of 15 ft. 9 in. per minute. This mill is guaranteed to crush thoroughly and efficiently from 250 to 300 tons of canes in 24 hours. In Louisiana two mills, set one behind the other, each with three rollers 32 in. in diameter by 78 in. long, and driven by one engine through gearing of 15 to 1, are speeded to have a surface velocity of rollers of 25 ft. 6 in. per minute (or 60% more than that of the French mill described above), and they are efficiently crushing 900 to 1200 tons of canes in 24 hours. In Australia, Demerara, Cuba, Java and Peru double crushing and maceration (first used on a commercial scale in Demerara by the late Hon. William Russell) have been generally adopted; and in many places, especially in the Hawaiian Islands, triple crushing (i.e. passing the canes through three consecutive sets of rollers, in order to extract everything possible of extraction by pressure) is employed. In the south of Spain, in some favoured spots where sugar-canes can be grown, they are submitted even to four successive crushings.

It has been found in practice advantageous to prepare the canes for crushing in the mills, as above described, by passing them through a pair of preparing rolls which are grooved or indented in such manner as to draw in and flatten down the canes, no matter in which way they are thrown or heaped upon the canecarrier, and thus prepare them for feeding the first mill of the series; thus the work of crushing is carried on uninterruptedly and without constant stoppages from the mills choking, as is often the case when the feed is heavy and the canes are not prepared.

Although it cannot be said that any one system of extraction is the best for all places, yet the following considerations are of general application: - a. Whatever pressure be brought to bear upon it, the vegetable or woody fibre of crushed sugar-canes will hold and retain for the from moment a quantity of moisture equal to its own weight, Yield . and in practice 10% more than its own weight; or in Crushing other words, loo lb of the best crushed megass will consist of 47.62 lb of fibre and 52.38 lb of moisture - that is, water with sugar in solution, or juice.

b. Canes vary very much in respect of the quality and also as to the quantity of the juice they contain. The quantity of the juice is the test to which recourse must be had in judging the efficiency of the extraction, while the quality is the main factor to be taken into account with regard to the results of subsequent manufacture.

For the application of the foregoing considerations to practice, the subjoined table has been prepared. It shows the greatest quantity of juice that may be expressed from canes, according to the different proportions of fibre they contain, but without employing maceration or imbibition, to which processes reference is made hereafter. The percentages are percentages of the original weight of the uncrushed canes.

	Per Cent.	Per Cent.	Per Cent.	Per Cent.	Per Cent.	Per Cent.
Percentage of fibre in canes .	10	II	12	13	14	15
Percentage of juice in canes .	90	89	88	87	86	85
Percentage of juice retained in me- gass. .. .	10	II	12	13	14	15
Percentage of maxi- mum expression.	80	78	76	74	72	70
Percentage of best average expres- sion, in practice.	79	76.9	74.9	72.9	70.6	68.5
Percentage of juice left in megass, in practice. .	II	12.1	13.2	14.3	15.4	16.5

The British Guiana Planters' Association appointed a sub-committee to report to the West India Commission on the manufacture of sugar, who stated the following: With canes containing 12% fibre the following percentages of sugar are extracted from the canes in the form of juice: Single crushing 76% Double crushing 85% Double crushing with 12% dilution 88% Triple crushing with Io% dilution. Diffusion with 25% dilution.. These results are equivalent to 66.88% extraction for single crushing. „ double crushing.

„ double crushing with 12% dilution. 0 „ triple to /o „ diffusion with 25% To prevent the serious loss of juice left in the megass by even the best double and triple crushing, maceration or imbibition was introduced. The megass coming from the first mill was saturated with steam and water, in weight equal to between 20% and 30% and up to 40% of the original weight of the uncrushed canes. Consequently, after the last crushing the mixture retained by the residual megass was not juice, as was the case when crushing was employed without maceration, but juice mixed with water; and it was found that the loss in juice was reduced by one-half. A further saving of juice was sometimes possible if the market prices of sugar were such as to compensate for the cost of evaporating an increased quantity of added water, but a limit was imposed by the fact that water might be used in excess. Hence in the latest designs for large factories it has been proposed that as much normal juice as can be extracted by double crushing only shall be treated by itself, and that the megass shall then be soused with twice as much water as there is juice remaining in it; after which, on being subjected to a third crushing, it will yield a degraded juice, which would also be treated by itself. It is found that in reducing the juice of these two qualities to syrup, fit to pass to the vacuum pans for cooking to crystals, the total amount of evaporation from the degraded j uice is about half that required from the normal juice produced by double crushing.

Great improvements have been made in the means of feeding the mills with canes by doing away with hand labour and substituting mechanical feeders or rakes, which by means of a simple steam-driven mechanism will rake the canes from the cane waggons on to the cane-carriers. By the adoption of this system in one large plantation in the West Indies, crushing upwards of 1200 tons of canes per day, the labour of sixty-four hands was dispensed with, and was thus made available for employment in the fields. In Louisiana the use of mechanical feeders is almost universal.

With a view of safeguarding themselves from breakdowns caused by the inequality of feeding, or by the action of malicious persons introducing foreign substances, such as crowbars, bolts, &c., among the canes, and so into the mills, many planters have adopted socalled hydraulic attachments, applied either to the megass roll or the top roll bearings. These attachments, first invented by Jeremiah Howard, and described in the United States Patent Journal in 1858, are simply hydraulic rams fitted into the side or top caps of the mill, and pressing against the side or top brasses in such a manner as to allow the side or top roll to move away from the other rolls, while an accumulator, weighted to any desired extent, keeps a constant pressure on each of the rams. An objection to the top cap arrangement is, that if the volume or feed is large enough to lift the top roll from the cane roll, it will simultaneously lift it from the megass roll, so that the megass will not be as well pressed as it ought to be;' and an objection to the side cap arrangement on the megass roll as well as to the top cap arrangement is, that in case more canes are fed in at one end of the rolls than at the other, the roll will be pushed out farther at one end than at the other; and though it may thus avoid a breakdown of the rolls, it is apt, in so doing, to break the ends off the teeth of the crown wheels by putting them out of line with one another. The toggle-joint attachment, which is an extremely ingenious way of attaining the same end as the hydraulic attachments, is open to the same objections.

Extraction of cane juice by diffusion (a process more fully described under the head of beetroot sugar manufacture) is adopted in a few plantations in Java and Cuba, in Louisiana Etr cti o n and the Hawaiian Islands, and in one or two factories y f i in Egypt; b u t hitherto, except under exceptional conditions (as at Aska, in the Madras Presidency, where the local price for sugar is three or four times the London price), it would not seem to offer any substantial advantage over double or triple crushing. With the latter system practically as much sugar is obtained from the canes as by diffusion, and the resulting megass furnishes, in a well-appointed factory, sufficient fuel for the crop. With diffusion, however, in addition to the strict scientific control necessary to secure the benefits of the process, fuel - that is, coal or wood - has to be provided for the working off of the crop, since the spent chips or slices from the diffusers are useless for this purpose; although it is true that in some plantations the spent chips have to a certain extent been utilized as fuel by mixing them with a portion of the molasses, which otherwise would have been sold or converted into rum. The best results from extraction by diffusion have been obtained in Java, where there is an abundance of clear, good water; but in the Hawaiian Islands, and in Cuba and Demerara, diffusion has been abandoned on several well mounted estates and replaced by double and triple crushing; and it is not likely to be resorted to again, as the extra cost of working is not compensated by the slight increase of sugar produced. In Louisiana diffusion is successfully worked on two or three large estates; but the general body of planters are shy of using it, although there is no lack of water, the Mississippi being near at hand.

Purification

The second operation is the coagulation of the albumen, and the separation of it with other impurities from the Maceration or Imbibition.  ? 90% 94% 74.80% 77.44% 79.20% 82.72% Mechanical ments. juice which holds them in suspension or solution. The moment the juice is expelled from the cells of the canes chemical inversion commences, and the sooner it is stopped the better. This is effected by the addition of lime to neutralize the free acid. As cold juice has a greater affinity for lime than hot juice, it is best to treat the juice with lime when cold. This is easily done in liming or measuring tanks of known capacity, into which the juice is run from the mill. The requisite amount of milk of lime set up at to° Beaume is then added. Cream of lime of 17° Beaume is sometimes used, but the weaker solution is preferable, since the proper proportion is more easily adjusted. In Demerara and other places the juice is then heated under pressure up to 220° F. to 250° F. for a few moments, on its way to a steam and juice separator, where the steam due to the superheated juice flashes off, and is either utilized for aiding the steam supplied to the multiple effect evaporators, or for heating cold juice on its way to the main heater, or it is allowed to escape into the atmosphere. The boiling juice is run down into subsiding tanks, where it cools, and at the same time the albumen, which has been suddenly coagulated by momentary exposure to high temperature, falls to the bottom of the tank, carrying with it the vegetable and other matters which were in suspension in the juice. After reposing some time, the clear juice is carefully decanted by means of a pipe fixed by a swivel joint to an outlet in the bottom of the tank, the upper end of the pipe being always kept at the surface of the liquor by a float attached to it. Thus clear liquor alone is run off, and the mud and cloudy liquor at the bottom of the tank are left undisturbed, and discharged separately as required.

In Australia a continuous juice separator is generally used, and preferred to ordinary subsiding or filtering tanks. It is a cylin drical vessel about 6 ft. deep, fitted with a conical bottom of about the same depth. Such a vessel is a. conveniently made of diameter which will give the cylindrical portion sufficient capacity to hold the juice expressed from the cane-mill in one hour. The hot liquor is conducted downwards in a continuous steady stream by a central pipe to eight horizontal branches, from which it issues into the separator at the level of the junction of the cylindrical and conical portions of the vessel. Since the specific gravity of hot liquor is less than that of cold liquor, and since the specific gravity of the scum and particles of. solid matter in suspension varies so slightly with the temperature that practically it remains constant, the hot liquor rises to the top of the vessel, and the scums 'and particles of solid matter in suspension separate themselves from it and fall to the bottom. By the mode of admission the hot liquor at its entry is distributed over a large area relatively to its volume, and while this is necessarily effected with but little disturbance to the contents of the vessel, a very slow velocity is ensured for the current of ascending juice. In a continuous separator of which the cylindrical portion measures 13 ft. in diameter and 6 ft. deep (a suitable size for treating a juice supply of 4000 to 4500 gallons per hour), the upward current will have a velocity of about i inch per minute, and it is found that all the impurities have thus ample time to separate themselves. The clear juice when it arrives at the top of the separator flows slowly over the level edges of ,a cross canal and passes in a continuous stream to the service tanks of the evaporators or vacuum pan. The sloping sides of the conical bottom can be freed from the coating of scum which forms upon them every two or three hours by two rotatory scrapers, formed of L-irons, which can be slowly turned by an attendant by means of a central shaft provided with a suitable handle. The scums then settle down to the bottom of the cone, whence they are run off to the scum tank. Every twenty-four hours or so the flow of juice may be conveniently stopped, and, after all the impurities have subsided, the superincumbent clear liquor may be decanted by a cock placed at the side of the cone for the purpose, and the vessel may be washed out. These separators are carefully protected by non-conducting cement and wood lagging, and are closed at the top to prevent loss of heat; and they will run for many hours without requiring to be changed, the duration of the run depending on the quality of the liquor treated and amount of impurities therein. Smaller separators of the same construction are used for the treatment of syrup.

In Cuba, Martinique, Peru and elsewhere the old-fashioned double-bottomed defecator is used, into which the juice is run direct, and there limed and heated. This defecator is made with a hemispherical copper bottom, placed in. an outer cast-iron casing, which forms a steam jacket, and is fitted with a cylindrical curb or breast above the bottom. If double-bottomed defecators are used in sufficient number to allow an hour and a half to two hours for making each defecation, and if they are of a size which permits any one of them to be filled up by the cane-mill with juice in ten to twelve minutes, they will make as perfect a defecation as is obtainable by any known system; but their employment involves the expenditure of much high-pressure steam (as exhaust steam will not heat the juice quickly enough through the small surface of the hemispherical inner bottom), and also the use of filter presses for treating the scums. A great deal of skilled superintendence is also required, and first cost is comparatively large. When a sufficient number are not available for a two hours' defecation, it is the practice in some factories to skim off the scums that rise to the top, and then boil up the juice for a few minutes and skim again, and, after repeating the operation once or twice, to run off the juice to separators or subsiders of any of the kinds previously described. In Java and Mauritius, where very clean canes are grown, double-bottomed defecators are generally used, and to them, perhaps as much as to the quality of the canes, may be attributed the very strong, fine sugars made in those islands. They are also employed in Egypt, being remnants of Lhe plant used in the days when the juice passed through bone-black before going to the evaporators.

A modification of the system of double-bottom defecators has lately been introduced with considerable success in San Domingo and in Cuba, by which a continuous and steady discharge of clear defecated juice is obtained on the one hand, and on the other a comparatively hard dry cake of scum or cachaza, and without the use of filter presses. These results are brought about by adding to the cold juice as it comes from the mill the proper proportion of milk of lime set up at 8° B., and then delivering the limed juice in a constant steady stream as near the bottom of the defecator as possible; it is thus brought into immediate contact with the heating surface and heated once for all before it ascends, with the result of avoiding the disturbance caused in the ordinary defecator by pouring cold juice from above on to the surface of the heated juice, and so establishing down-currents of cold juice and up-currents of hot juice. In the centre of the defecator an open-topped cylindrical vessel is placed, with its bottom about 6 in. above the bottom of the defecator and its top about 12 in. below the top of the defecator. In this vessel is placed the short leg of a draw-off siphon, reaching to nearly the bottom. The action of the moderate heat, 210° F., on the limed juice causes the albumen in it to coagulate; this rising to the surface collects the cachazas, which form and float thereon. The clear juice in the meantime flows over the edge of the cylindrical vessel without disturbance and finds its way out by the short leg of the siphon, and so passes to the canal for collecting the defecated juice. The admission of steam must be regulated with the greatest nicety, so as to maintain an equable temperature, 208° to 210° F., hot enough to act upon the albumen and yet not enough to cause ebullition or disturbance in the juice, and so prevent a proper separation of the cachazas. This is attained by the aid of a copper pipe, 4 in. in diameter, which follows the curve of the hemispherical bottom, and is fitted from one side to the other of the defecator; one end is entirely closed, and the other is connected by a small pipe to a shallow circular vessel outside the defecator, covered with an india-rubber diaphragm, to the centre of which is attached a light rod actuating a steam throttle-valve, and capable of being adjusted as to length, &c. The copper pipe and circular vessel are filled with cold water, which on becoming heated by the surrounding juice expands, and so forces up the india-rubber diaphragm and shuts off the steam. By adjusting the length of the connecting rod and the amount of water in the vessel, the amount of steam admitted can be regulated to a nicety. To make this apparatus more perfectly automatic, an arrangement for continually adding to and mixing with the juice the proper proportion of milk of lime has been adapted to it; and although it may be objected that once the proportion has been determined no allowance is made for the variation in the quality of the juice coming from the mill owing to the variations that may occur in the canes fed into the mills, it is obviously as easy to vary the proportion with the automatic arrangement from time to time as it is to vary in each separate direction, if the man in charge will take the trouble to do so, which he very seldom does with the ordinary defecators, satisfying himself with testing the juice once or twice in a watch. The scums forming on the top of the continuous defecator become so hard and dry that they have to be removed from time to time with a specially constructed instrument like a flat spade with three flat prongs in front. These scums are not worth passing through the filter presses, and are sent to the fields direct as manure.

The scums separated from the juice by ordinary defecation entangle and carry away with them a certain amount of the juice with its contained saccharine. In some factories they are collected in suitable tanks, and steam is blown into them, which further coagulates the albuminous par Scums. tides. These in their upward passage to the top, where they float, free themselves from the juice, which they leave below them comparatively clear. The juice is then drawn off and pumped up to one of the double-bottomed defecators and redefecated, or, where juice-heaters have been used instead of defecators, the scums from the separators or subsiders are heated and forced through filter presses, the juice expressed going to the evaporators and the scum cakes formed in the filter presses to the fields as manure.

In diffusion plants the milk of lime is added, in proper proportion, in the cells of the diffusion battery, and the chips or slices themselves act as a mechanical filter for the juice; while in the Sandwich Islands coral-sand filters have been employed for some years, in addition to the chips, to free the juice from impurities held in mechanical suspension. In Germany very similar filters have also been used, pearl-quartz gravel taking the place of coral sand, which it closely resembles. In Mexico filters filled with dry powdered megass have been found very efficient for removing the large quantity of impurities contained in the juice expressed from the very vigorous but rank canes grown in that wonderfully fertile country, but unless constant care is taken in managing them, and in changing them at the proper time, there is great risk of inversion taking place, with consequent loss of sugar.

After the juice has been defecated or purified by any of the means above mentioned it is sent to the evaporating apparatus, hereinafter described, where it is concentrated to 26° or 28° Beaume, and is then conducted in a continuous stream either into the service tanks of the vacuum pan, if dark sugars are required, or, if a better colour is wanted, into clarifiers. The latter are circular or rectangular vessels, holding from 500 to 1500 gallons each, according to the capacity of the factory, and fitted with steam coils at the bottom and skimming troughs at the top. In them the syrup is quickly brought up to the boil and skimmed for about five minutes, when it is run off to the service tanks of the vacuum pans. The heat at which the syrup boils in the clarifiers, 220° F., has the property of separating a great deal of the gum still remaining in it, and thus cleansing the solution of sugar and water for crystallization in the vacuum pans; and if after skimming the syrup is run into separators or subsiders of any description, and allowed to settle down and cool before being drawn into the vacuum pan for crystallization, this cleansing process will be more thorough and the quality of the final product will be improved. Whether the improvement will be profitable or not to the planter or manufacturer depends on the market for the sugar, and on the conditions of foreign tariffs, which are not infrequently hostile.

Evaporation of the Juice to Syrup. - The third operation is the concentration of the approximately pure, but thin and watery, juice to syrup point, by driving off a portion of the water in vapour through some system of heating and evaporation. Since on an average 70% by measurement of the normal defecated cane juice has to be evaporated in order to reduce it to syrup ready for final concentration and crystallization in the vacuum pan, and since to attain the same end as much as 90 to 95% of the volume of mixed juices has to be evaporated when maceration or imbibition is employed, it is clear that some more economical mode of evaporation is necessary in large estates than the open-fire batteries still common in Barbados and some of the West Indian islands, and in small haciendas in Central America and Brazil, but seldom seen elsewhere. With open-fire batteries for making the syrup, which was afterwards finished in the vacuum pan, very good sugar was produced, but at a cost that would be ruinous in to-day's markets.

In the best days of the so-called Jamaica Trains in Demerara, three-quarters of a ton of coal in addition to the megass was burned per ton of sugar made, and with this for many years planters were content, because they pointed to the fact that in the central factories, then working in Martinique and Guadeloupe, with charcoal filters and triple-effect evaporation, 750 kilos of coal in addition to the megass were consumed to make woo kilos of sugar. All this has now been changed. It is unquestionably better and easier to evaporate in vacuo than in an open pan, and with a better system of firing, a more liberal provision of steam generators, and multiple-effect evaporators of improved construction, a far larger yield of sugar is obtained from the juice than was possible of attainment in those days, and the megass often suffices as fuel for the crop.

The multiple-effect evaporator, originally invented and constructed by Norberto Rilleux in New Orleans in 1840, has under gone many changes in design and construction since Effect that year. The growing demand for this system of evaporation for application in many other industries, besides that of sugar has brought to the front a large number of inventors. Forgetful or ignorant of the great principle announced and established by Rilleux, they have mostly devoted their energies and ingenuity to contriving all sorts of complicated arrangements to give the juice the density required, by passing and repassing it over the heating surface of the apparatus, the saving of a few square feet of which would seem to have been their main object. In some instances the result has been an additional and unnecessary expenditure of high-pressure steam, and in all the weld-known fact - of the highest importance in this connexion - appears to have been disregarded, that the shorter the time the juice is exposed to heat the less inversion will take place in it, and therefore the less will be the loss of sugar. But this competition among inventors, whatever the incentive, has not been without benefit, because to-day, by means of very simple improvements in details, such as the addition of circulators and increased area of connexions, what may be taken to be the standard type of multiple-effect evaporator (that is to say, vertical vacuum pans fitted with vertical heating tubes, through which passes the liquor to be treated, and outside of which the steam or vapour circulates) evaporates nearly double the quantity of water per square foot of heating surface per hour which was evaporated by apparatus in use so recently as 1885 - and this without any increase in the steam pressure. That evaporation in vacuo, in a multiple-effect evaporator, is advantageous by reason of the increased amount of sugar obtained from a given quantity of juice, and by reason of economy of fuel, there is no doubt, but whether such an apparatus should be of double, triple, quadruple or quintuple effect will depend very much on the amount of juice to be treated per day, and the cost of fuel. Thus, supposing that moo lb of coal were required to work a single vacuum pan, evaporating, say, 6000 lb of water in a given time, then 500 lb of coal would be required for a double-effect apparatus to do the same work, 333 lb for a triple effect, 250 for a quadruple effect, and 200 lb for a quintuple effect. In some places where coal costs 60s. a ton, and where steam is raised by coal, as in a beetroot factory, it might pay to adopt a quintuple-effect apparatus, but on a cane-sugar estate, where the steam necessary for the evaporator is raised by burning the megass as fuel, and is first used in the engines workifig the mills, the exhaust alone passing to the evaporator, there would be very little, if any, advantage in employing a quadruple effect instead of a triple effect, and practically none at all in having a quintuple-effect apparatus, for the interest and sinking fund on the extra cost would more than counterbalance the saving in fuel.

With the juice of some canes considerable difficulty is encountered in keeping the heating surfaces of the evaporators clean and free from incrustations, and cleaning by the use of acid has to be resorted to. In places where work is carried on day and night throughout the week, the standard type of evaporator lends itself more readily to cleaning operations than any other. It is obviously easier to brush out and clean vertical tubes open at both ends, and about 6 ft. long, on which the scale has already been loosened by the aid of boiling with dilute muriatic acid or a weak solution of caustic soda in water, than it is to clean either the inside or the outside of horizontal tubes more than double the length. This consideration should be carefully, remembered in the future by the planter who may require an evaporator and by the engineer who may be called upon to design or construct it, and more especially by a constructor without practical experience of the working of his constructions.

Concentration and Crystallization

The defecated cane juice, having lost about 70% of its bulk by evaporation in the multipleeffect evaporator, is now syrup, and ready to enter the vacuum pan for further concentration and crystallizaHoward's tion. In a patent (No. 3607, 1812) granted to E. C.

Howard it is stated, among other things, that " water Pan. dissolves the most uncrystallizable in preference to that which is most crystallizable sugar," and the patentee speaks of " a discovery I have made that no solution, unless highly concentrated, of sugar in water can without material injury to its colouring-and crystallizing power, or to both, be exposed to its boiling temperature during the period required to evaporate such solution to the crystallizing point." He stated that " he had made a magma of sugar and water at atmospheric temperature, and heated the same to 190° or 200° F. in a water or steam bath, and then added more sugar or a thinner magma, and the whole being then in a state of imperfect fluidity, but so as to close readily behind the stirrer, was filled into moulds and purged " (drained). " I do further declare," he added, " that although in the application of heat to the refining of sugar in my said invention or process I have stated and mentioned the temperature of about 200° F. scale as the heat most proper to be used and applied in order to secure and preserve the colour and crystallizability of the sugars, and most easily to be obtained with precision and uniformity by means of the water bath and steam bath, yet when circumstances or choice may render the same desirable I do make use of higher temperatures, although less beneficial." Howard at any rate saw clearly what was one of the indispensable requisites for the economical manufacture of fine crystal sugar of good colour - the treatment of saccharine solutions at temperatures very considerably lower than 212° F., which is the temperature of water boiling at normal atmospheric pressure. Nor was he long in providing means for securing these lower temperatures. His patent (No. 3754 of 1813) describes the closed vacuum pan and the air pump with condenser for steam by injection, the use of a thermometer immersed in the solution in the pan, and a method of ascertaining the density of the solution with a proof stick, and by observations of the temperature at which, while fluid and not containing grain, it could be kept boiling under different pressures shown by a vacuum gauge. A table is also given of boiling points from 115° F. to 175° F., corresponding to decimal parts of an inch of mercury of the vacuum gauge. Since Howard published his invention the vacuum pan has been greatly improved and altered in shape and power, and especially of recent years, and the advantages of concentrating in vacuo having been acknowledged, the system has been adopted in many other industries, and crowds of inventors have turned their attention to the principle. In endeavouring to make a pan of less power do as much and as good work as one of greater power, they have imagined many ingenious mechanical contrivances, such as currents produced mechanically to promote evaporation and crystallization, feeding the pan from many points in order to spread the feed equally throughout the mass of sugar being cooked, and so on. All their endeavours have obtained at best but a doubtful success, for they have overlooked the fact that to evaporate a given weight of water from the syrup in a vacuum pan at least an equal weight (or in practice about 15% more) of steam must be condensed, and the first cost of mechanical agitators, together with the expenditure they involve for motive power and maintenance, must be put against the slight saving in the heating surface effected by their employment. On the other hand, the advocates of admitting the feed into a vacuum pan in many minute streams appeal rather to the ignorant and incompetent sugarboiler than to a man who, knowing his business thoroughly, will boil 150 tons of hot raw sugar in a pan in a few hours, feeding it through a single pipe and valve io in. in diameter. Nevertheless, it has been found in practice, when syrups with low quotient of purity and high quotient of impurity are being treated, injecting the feed at a number of different points in the pan does reduce the time required to boil the pan, though of no practical advantage with syrups of high quotient of purity and free from the viscosity which impedes circulation and therefore quick boiling. Watt, when he invented the steam engine, laid down the principles on which it is based, and they hold good to the present day. So also the principles laid down by Howard with respect to the vacuum pan hold good to-day: larger pans have been made and their heating surface has been increased, but it has been found by practice now, as it was found then, that an ordinary worm or coil 4 in. in diameter and 50 ft. long will be far more efficient per square foot of surface than a similar coil ioo ft. long. Thus the most efficient vacuum pans of the present day are those which have their coils so arranged that no portion of them exceeds 50 or 60 ft. in length; with such coils, and a sufficient annular space in the pan free from obstruction, in order to allow a natural down-current of the cooking mass, while an up-current all round is also naturally produced by the action of the heated worms or coils, rapid evaporation and crystallization can be obtained, without any mechanical adjuncts to require attention or afford excuse for negligence.

The choice of the size of the crystals to be produced in a given pan depends upon the market for which they are intended. It is of course presupposed that the juice has been properly defecated, because without this no amount of skill and knowledge in cooking in the pan will avail; the sugar resulting must be bad, either in colour or grain, or both, and certainly in polarizing power. If a very large firm grain like sugar-candy is required the syrup when first brought into the pan must be of low density, say 20° to 21° Beaume, but if a smaller grain be wanted it can easily be obtained from syrup of 27° to 28° Beaume. On some plantations making sugar for particular markets and use in refineries it is the custom to make only one class of sugar, by boiling the molasses produced by the purging of one strike with the sugar in the next strike. On other estates the second sugars, or sugars produced from boiling molasses alone, are not purged to dryness, but when sufficiently separated from their mother-liquor are mixed with the defecated juice, thereby increasing its saccharine richness, and after being converted into syrup in the usual manner are treated in the vacuum pan as first sugars, which in fact they really are.

In certain districts, notably in the Straits Settlements, syrup is prepared as described above for crystallization in a vacuum pan, but instead of being cooked in vacuo it is slowly boiled up in open double-bottom pans. These pans are sometimes heated by boiling oil, with the idea that under such conditions the sugar which is kept stirred all the time as it thickens cannot be burnt or caramelized; but the same object can be attained more economically with steam of a given pressure by utilizing its latent heat. The sugar thus produced, by constant stirring and evaporation almost to dryness, forms a species of small-grained concrete. It is called " basket sugar," and meets with a brisk sale, at remunerative prices, among the Chinese coolies; and as the sugar as soon as cooled is packed ready for market, without losing any weight by draining, this branch of sugar-making is a most lucrative one whereever there is sufficient local demand. Very similar kinds of sugar are also produced for local consumption in Central America and in Mexico, under the names of " Panela " and " Chancaca," but in those countries the sugar is generally boiled in pans placed over special fire-places, and the factories making it are on a comparatively small scale, whereas in the Straits Settlements the " basket sugar " factories are of considerable importance, and are fitted with the most approved machinery.

Curing or Preparation of Crystals for the Market

The crystallized sugar from the vacuum pan has now to be separated from the molasses or mother-liquor surrounding the crystals. In some parts of Mexico and Central America this separation is still effected by running the sugar into conical moulds, and placing on the top a layer of moist clay or earth which has been kneaded in a mill into a stiff paste. The moisture from the clay, percolating through the mass of sugar, washes away the adhering molasses and leaves the crystals comparatively free and clear. It may be noted that sugar that will not purge easily and freely with clay will not purge easily and freely in centrifugals. But for all practical purposes the system of claying sugar is a thing of the past, and the bulk of the sugar of commerce is now purged in centrifugals, as indeed it has been for many years. The reason is obvious. The claying system involved the expense of large curing houses and the employment of many hands, and forty days at least were required for completing the operation and making the sugar fit for the market, whereas with centrifugals sugar cooked to-day can go to market to-morrow, and the labour employed is reduced to a minimum.

When Cuba was the chief sugar-producing country making clayed sugars it was the custom (followed in refineries and found advantageous in general practice) to discharge the strike of crystallized sugar from the vacuum pan into a receiver heated below by steam, and to stir the mass for a certain time, and then distribute it into the moulds in which it was afterwards clayed. When centrifugals were adopted for purging the whole crop (they had long been used for curing the second or third sugars), the system then obtaining of running the sugar into wagons or coolers, which was necessary for the second and third sugars' cooked only to string point, was continued, but latterly " crystallization in movement, a development of the system which forty years ago or more existed in refineries and in Cuba, has come into general use, and with great advantage, especially where proprietors have been able to erect appropriate buildings and machinery for carrying out the system efficiently. The vacuum pan is erected at a height which commands the crystallizers, each of which will, as in days gone by in Cuba, hold the contents of the pan, and these in their turn are set high enough to allow the charge to fall into the feeding-trough of the centrifugals, thus obviating the necessity of any labour to remove the raw sugar from the time it leaves the vacuum pan to the time it falls into the centrifugals. For this reason alone, and without taking into consideration any increase in the yield of sugar brought about by " crystallization in movement," the system is worthy of adoption in all sugar factories making crystal sugar.

The crystallizers are long, horizontal, cylindrical or semi-cylindrical vessels, fitted with a strong horizontal shaft running from end to end, which is kept slowly revolving. The shaft Crystal- carries arms and blades fixed in such a manner that the mass of sugar is quietly but thoroughly moved, while at the same time a gentle but sustained evaporation is produced by the continuous exposure of successive portions of the mass to the action of the atmosphere. Thus also the crystals already formed come in contact with fresh mother-liquor, and so go on adding to their size. Some crystallizers are made entirely cylindrical, and are connected to the condenser of the vacuum pan; in order to maintain a partial vacuum in them, some are fitted with cold-water pipes to cool them and with steam pipes to heat them, and some are left open to the atmosphere at the top. But the efficiency of all depends on the process of almost imperceptible yet continuous evaporation and the methodical addition of syrup, and not on the idiosyncrasies of the experts who manage them; and there is no doubt that in large commercial processes of manufacture the simpler the apparatus used for obtaining a desired result, and the more easily it is understood, the better it will be for the manufacturer. The sugar made from the first syrups. does not require a crystallizer in movement to prepare it for purging in the centrifugals, but it is convenient to run the strike into the crystallizer and so empty the pan at once and leave it ready to commence another strike, while the second sugars will be better for twenty-four hours' stirring and the third sugars for forty-eight hours' stirring before going to the centrifugals. To drive these machines electricity has been applied, with indifferent success, but they have been very efficiently driven, each independently of the others in the set, by means of a modification of a Pelton wheel, supplied with water under pressure from a pumping engine. A comparatively small stream strikes the wheel with a pressure equivalent to a great head, say 300 ft., and as the quantity of water and number of jets striking the wheel can be regulated with the greatest ease and nicety, each machine can without danger be quickly brought up to its full speed when purging high-class sugars, or allowed to run slowly when purging low-class sugars, until the heavy, gummy molasses have been expelled; and it can then be brought up to its full speed for finally drying the sugar in the basket, a boon which all practical sugar-makers will appreciate. The water forced by the force-pump against the Pelton wheels returns by a waste-pipe to the tank, from which the force-pump takes it again.

Recent Progress

The manufacture of cane sugar has largely increased in volume since the year 1901-1902. This, apart from the effect of the abolition of the sugar bounties, has been mainly the result of the increased employment of improved processes, carried on in improved apparatus, under skilled supervision, and with due regard to the importance of the chemical aspects of the work.

Numerous central factories have been erected in several countries with plant of large capacity, and many of them work day and night for six days in the week. There were 173 of these factories working in Cuba in 1908-1909, among which the " Chaparra," in the province of Oriente, turned out upwards of 69,000 tons of sugar in the crop of about 20 weeks, and the " Boston " had an output of about 61,00o tons in the same time. Of the 178 factories at work in Java in 1908-1909, nearly all had most efficient plant for treating the excellent canes grown in that favoured island. (See Jaarboek voor suikerfabrikanten op Java, 13 e Jaargang 1908-1909, pp. 22-61, Amsterdam, J. H. de Bussy.) The severance of the agricultural work, i.e. cane-growing, from the manufacturing work, sugar-making, must obviously conduce to better and more profitable work of both kinds.

The use of multiple-effect evaporation made it possible to raise the steam for all the work required to be done in a well-equipped factory, making crystals, under skilful management, by means of the bagasse alone proceeding from the. canes ground, without the aid of other fuel. The bagasse so used is now commonly taken straight from the cane mill to furnaces specially designed for burning it, in its moist state and without previous drying, and delivering the hot gases from it to suitable boilers, such as those of the multitubular type or of the water-tube type. The value of fresh bagasse, or as it is often called " green " bagasse, as fuel varies with the kind of canes from which it comes, with their treatment in the mill, and with the skill used in firing; but it may be stated broadly that I lb of fresh bagasse will produce from I a lb to 24 lb of steam, according to the conditions.

The use of preparing rolls with corrugations, to crush and equalize the feed of canes to the mill, or to the first of a series of mills, has become general. The Krajewski crusher has two such E steel rolls, with V-shaped corrugations extending longi tudinally across them. These rolls run at a speed about 30% greater than the speed of the first mill, to which they deliver the canes well crushed and flattened, forming a close mat of pieces of cane 5 to 6 in. long, so that the subsequent grinding can be carried on without the stoppages occasioned by the mill choking with a heavy and irregular feed. The crusher is preferably driven by an independent engine, but with suitable gearing it can be driven by the mill engine. The Krajewski crusher was invented some years ago by a Polish engineer resident in Cuba, who took out a patent for it and gave it his name. The patent has expired. The increase in the output for a given time obtained by the use of the Krajewski crusher has been estimated at 20 to 25% and varies with the quality of the canes; while the yield of juice or extraction is increased by I or 2%.

The process of continuous defecation which was introduced into Cuba from Santo Domingo about 1900 had by 1910 borne the test of some ten years' use with notable success. The Hatton defecator, which is employed for working it, has been already described, but it may be mentioned that the regulation of the admission of steam is now simplified and secured. by a patent thermostat - a self-acting apparatus in which the unequal expansion of different metals by heat actuates, through compressed air, a diaphragm which controls the steam stop-valve - and by this means a constant temperature of 210° F. (98.8° C.) is maintained in the juice within the defecator during the whole time it is at work.

Earthy matter and other matter precipitated and fallen on the copper double bottom may be dislodged by a slowly revolving scraper - say every twelve hours - and ejected through the bottom discharge cock; and thus the heating surface of the copper bottom will be kept in full efficiency. With ordinary care on the part of the men in charge Hatton defecators will work continuously for several days and nights, and the number required to deal with a given volume of juice is half the number of ordinary defecators of equal capacity which would do the same work; for it must be borne in mind that an ordinary double-bottomed defecator takes two hours to deliver its charge and be in readiness to receive a fresh charge, i.e. 20 minutes for filling and washing out after emptying; 60 minutes for heating up and subsiding; and 40 minutes for drawing off the defecated juice, without agitating it. Apart from increased yield in sugar of good quality, we may sum up the advantages procurable from the use of Hatton defecators as follows: cold liming; heating gently to the temperature required to coagulate the albumen and not beyond it, whereby disturbance would ensue; the continuous separation of the scums; the gradual drying of the scums so as to make them ready for the fields, without carrying away juice or requiring treatment in filter presses; and the continuous supply of hot defecated juice to the evaporators, without the use of subsiding tanks or eliminators; and, finally, the saving in expenditure on plant, such as filter presses, &c., and wages.

Beetroot Sugar Manufacture

The sugar beet is a cultivated variety of Beta maritima (nat. ord. Chenopodiaceae), other varieties of which, under the name of mangold or mangel-wurzel, are grown as feeding roots for cattle.

About 1760 the Berlin apothecary Marggraff obtained in his laboratory, by means of alcohol, 6.2% of sugar from a white variety of beet and 4.5% from a red variety. At the present day, thanks to the careful study of many years, the improvements of cultivation, the careful selection of seed and suitable manuring, especially with nitrate of soda, the average beet worked up contains 7% of fibre and 93% of juice, and yields in Germany 12.79% and in France 11.6% of its weight in sugar. In Great Britain in 1910 the cultivation of beet for sugar was being seriously undertaken in Essex, as the result of careful consideration during several years. The pioneer experiments on Lord Denbigh's estates at Newnham Paddox, in XXVI. 2 a Warwickshire, in 1900, had produced excellent results, both in respect of the weight of the beets per acre and of the saccharine value and purity of the juice. The average weight per acre was over 252 tons, and the mean percentage of pure sugar in the juice exceeded Isl. The roots were grown under exactly the same cultivation and conditions as a crop of mangel-wurzel - that is to say, they had the ordinary cultivation and manuring of the usual root crops. The weight per acre, the saccharine contents of the juice, and the quotient of purity compared favourably with the best results obtained in Germany or France, and with those achieved by the Suffolk farmers, who between 1868 and 1872 supplied Mr Duncan's beetroot sugar factory at Lavenham; for the weight of their roots rarely reached 15 tons per acre, and the percentage of sugar in the juice appears to have varied between 10 and 12. On the best-equipped and most skilfully managed cane sugar estates, where the climate is favourable for maturing the cane, a similar return is obtained. Therefore, roughly speaking, one ton of beetroot may be considered 'to-day as of the same value as one ton of canes; the value of the refuse chips in one case, as food for cattle, being put against the value of the refuse bagasse, as fuel, in the other. Before beetroot had been brought to its present state of perfection, and while the factories for its manipulation were worked with hydraulic presses for squeezing the juice out of the pulp produced in the raperies, the cane sugar planter in the West Indies could easily hold his own, notwithstanding the artificial competition created and maintained by sugar bounties. But the degree of perfection attained in the cultivation of the roots and their subsequent manipulation entirely altered this situation and brought about the crisis in the sugar trade referred to in connexion with the bounties (see History below) and dealt with in the Brussels convention of 1902.

In beetroot sugar manufacture the operations are washing, slicing, diffusing, saturating, sulphuring, evaporation, concentration and curing.

Slicing

The roots are brought from the fields by carts, canals and railways. They are weighed and then dumped into a washing machine, consisting of a large horizontal cage, submerged in water, in which revolves a horizontal shaft carrying arms. The arms are set in a spiral form, so that in revolving they not only stir the roots, causing them to rub against each other, but also force them forward from the receiving end,of the cage to the other end. Here they are discharged (washed and freed from any adherent soil) into an elevator, which carries them up to the top of the building and delivers them into a hopper feeding the slicer. Slicers used to be constructed with iron disks about 33 to 40 in. diameter, which were fitted with knives and made 140 to 150 revolutions per minute, under the hopper which received the roots. This hopper was divided into two parts by vertical division plates, against the bottom edge of which the knives in the disk forced the roots and sliced and pulped them. Such machines were good enough when the juice was expelled from the small and, so to speak, chopped slices and pulp by means of hydraulic presses. But hydraulic presses have now been abandoned, for the juice is universally obtained by diffusion, and the small slicers have gone out of use, because the large amount of pulp they produced in proportion to slices is not suitable for the diffusion process, in which evenly cut slices are required, which present a much greater surface with far less resistance to the diffusion water. Instead of the small slicers, machines made on the same principle, but with disks 7 ft. and upwards in diameter, are used. Knives are arranged around their circumference in such a way that the hopper feeding them presents an annular opening to the disk, say 7 ft. outside diameter and 5 ft. inside, with the necessary division plates for the knives to cut against, and instead of making 140 to 150 revolutions the disks revolve only 60 to 70 times per minute. Such a slicer is capable of efficiently slicing 300,000 kilos of roots in twenty-four hours, the knives being changed four times in that period, or oftener if required, for it is necessary to change them the moment the slices show by their rough appearance that the knives are losing their cutting edges.

Diffusion

The diffusion cells are closed, vertical, cylindrical vessels, holding generally 60 hectolitres, or 1320 gallons, and are arranged in batteries of 12 to 14. Sometimes the cells are erected in a circle, so that the spout below the slicing machine revolving above them with a corresponding radius can discharge the slices into the centre of any of the cells. In other factories the cells are arranged in lines and are charged from the slicer by suitable telescopic pipes or other convenient means. A circular disposition of the cells facilitates charging by the use of a pipe rotating above them, but it renders the disposal of the hot spent slices somewhat difficult and inconvenient. The erection of the cells in straight lines may cause some little complication in charging, but it allows the hot spent slices to be discharged upon a travelling band which takes them,to an elevator, an arrangement simpler than any which is practicable when the cells are disposed in a circle. Recently, however, a well-known sugar maker in Germany has altered his battery in such manner that instead of having to open a large door below the cells in order to discharge them promptly, he opens a comparatively small valve and, applying compressed air at the top of the cell, blows the whole contents of spent slices up a pipe to the drying apparatus, thus saving not only a great deal of time but also a great deal of labour of a kind which is both arduous and painful, especially during cold weather. The slices so blown up, or elevated, are passed through a mill which expels the surplus water, and are then pressed into cakes and dried until they hold about 12% of water and 88% of beet fibre. These cakes, sold as food for cattle, fetch as much as £4 per ton in Rumania, where four or five beetroot factories are now at work. A cell when filled with fresh slices becomes the head of the battery, and where skilled scientific control can be relied upon to regulate the process, the best and most economical way of heating the slices, previous to admitting the hot liquor from the next cell, is by direct steam; but as the slightest inattention or carelessness in the admission of direct steam might have the effect of inverting sugar and thereby causing the loss of some portion of saccharine in the slices, water heaters are generally used, through which water is passed and heated up previous to admission to the freshly-filled cell. When once a cell is filled up and the slices are warmed through, the liquor from the adjoining cell, which hitherto has been running out of it to the saturators, is turned into the new cell, and beginning to displace the juice from the fresh slices, runs thence to the saturators. When the new cell comes into operation and becomes the head of the battery, the first or tail cell is thrown out, and number two becomes the tail cell, and so the rounds are repeated; one cell is always being emptied and one filled or charged with slices and heated up, the latter becoming the head of the battery as soon as it is ready.

Saturation

The juice, previously treated with lime in the diffusion battery, flows thence into a saturator. This is a closed vessel, into which carbonic acid gas (produced as described hereafter) is forced, and combining with the lime in the juice forms carbonate of lime. The whole is then passed through filter presses, the clear juice being run off for further treatment, while the carbonate of lime is obtained in cakes which are taken to the fields as manure. The principal improvement made of recent years in this portion of the process has been the construction of pipes through which the carbonic acid gas is injected into the juice in such a manner that they can be easily withdrawn and a clean set substituted. The filter presses remain substantially unchanged, although many ingenious but slight alterations have been made in their details. The juice, which has now become comparatively clear, is again treated with lime, and again passed through a saturator and filter presses, and comes out still clearer than before. It is then treated with sulphurous acid gas, for the purpose of decolorization, again limed to neutralize the acid, and then passed through a third saturator wherein all traces of lime and sulphur are removed.

A process for purifying and decolorizing the juice expressed from beetroots by the addition of a small quantity of manganate of lime (20 to 50 grammes per hectolitre of juice), under the influence of an electric current, was worked with considerable success in a sugar factory in the department of Seine-et-Marne in the year 1900-1901. A saving of 40% is stated to be effected in lime. The use of sulphurous acid gas is entirely abandoned, and instead of three carbonatations with corresponding labour and plant only one is required. The coefficient of purity is increased and the viscosity of the juice diminished. The total saving effected is stated to be equivalent to 3 francs per ton of beetroot worked up. This system is also being tried on a small scale with sugar-cane juice in the West Indies. If by this process a more perfect defecation and purification of the juice is obtained, it will no doubt be highly beneficial to the cane p lanter, though no great economy in lime can be effected, because but very little is used in a cane factory in comparison with the amount used in a beet factory.

Evaporation and Crystallization

The clear juice thus obtained is evaporated in a multiple-effect evaporator and crystallized in a vacuum pan, and the sugar is purged in centrifugals. From the centrifugal the sugar is either turned out without washing as raw sugar, only fit for the refinery, or else it is well washed with a spray of water and air until white and dry, and it is then offered in the market as refined sugar, although it has never passed through animal charcoal (bone-black). The processes of evaporation and concentration are carried on as they are in a cane sugar factory, but with this advantage, that the beet solutions are freer from gum and glucose than those obtained from sugar-canes, and are therefore easier to cook.

Curing

There are various systems of purging refined, or socalled refined, sugar in centrifugals, all designed with a view of obtaining the sugar in lumps or tablets, so as to appear as if it had been turned out from moulds and not from centrifugals, and great ingenuity and large sums of money have been spent in perfecting these different systems, with more or less happy results. But the great achievement of recent manufacture is the production, without the use of animal charcoal, of a cheaper, but good and wholesome article, in appearance equal to refined sugar for all intents and purposes, except for making preserves of fruits in the old-fashioned way. The wholesale jam manufacturers of the present day use this sugar; they boil the jam in vacuo and secure a product that will last a long time without deteriorating, but it lacks the delicacy and distinctive flavour of fruit preserved by a careful housekeeper, who boils it in an open pan with cane sugar to a less density, though exposed for a short time to a greater heat.

Carbonatation

The carbonic acid gas injected into the highly limed juice in the saturators is made by the calcination of limestone in a kiln provided with three cleaning doors, so arranged as to allow the lime to be removed simultaneously from them every six hours. The gas generated in the kiln is taken off at the top by a pipe to a gas-washer. In this it passes through four sheets of water, by which it is not only freed from any dust and dirt that may have come over with it from the kiln, but is also cooled to a temperature which permits an air-pump to withdraw the gas from the kiln, through the gas-washer, and force it into the saturators, without overheating. In some factories for refining sugar made from beet or canes this system of carbonatation is used, and enables the refiner to work with syrups distinctly alkaline and to economize a notable amount of animal charcoal.

Refining

Briefly, sugar-refining consists of melting raw or unrefined sugar with water into a syrup of 27° to 28° Beaume, or 1230 specific gravity, passing it through filtering cloth to remove the sand and other matters in mechanical suspension, and then through animal charcoal to remove all traces of colouring matter and lime, thus producing a perfectly clear white syrup, which, cooked in the vacuum pan and crystallized, becomes the refined sugar of commerce.

Melting Pans

The melting pans are generally circular vessels, fitted with a perforated false bottom, on which the sugar to be melted is dumped. The pans are provided with steam worms to keep the mass hot as required, and with mechanical stirrers to keep it in movement and thoroughly mixed with the water and sweet water which are added to the sugar to obtain a solution of the specific gravity desired. Any sand or heavy matter in suspension