786 



SUGAR 



cannose, &c. ) is a solid crystallising in tlio fnnu of 

 monoclinic prisms generally with hcmihedral faces 

 which are transparent, colourless, and have a 

 sweet taste, a specific gravity of about 1 '6, a melt- 

 ing point of aliotit 160 C. , aud strongly rotate the 

 plane of polarisation to the right (see In-low '. 

 Sucrose is soluble in aliout half its weight of cold 

 water and in boiling water in all proportions ; it is 

 nearly insoluble in absolute alcohol and soluble in 

 dilute alcohol, the solubility increasing with the 

 dilution in an ascending ratio. I'.tlici. chloroform, 

 carbon dUulphide, oil of turpentine, petroleum 

 spirit, and liquids immiscible with water generally, 

 .have no solvent action upon this sugar. Sucrose 

 melts at about 160 C. (320 !'.), and assumes on 

 cooling the condition known as ' barley-sugar,' 

 which is probably an allotropic form; at a little 

 above the fusing-point it passes into a mixture of 

 dextrose and lievulosan without loss of water. 

 When still further heated water is given off, and 

 the mass begins to blacken with evolution of fumes 

 having a characteristic odour ; and at about 200 C. 

 caramel, a mixture of caramelan, CHiO, cara- 

 nieleii, CjuHsoOs, and caramelin, CWHunOsi, is 

 obtained. Caramel is largely used for the colour- 

 ing of wines, beer, vinegar, &c. Alkaline hydrox- 

 ides in the cold have little or no action on sucrose, 

 but when fused with caustic potash this sugar 

 yields oxalate and acetate of potassium. 



Solutions of sucrose possess tin- property of dis- 

 solving the oxides of the alkaline earths, with which 

 the sugar forms compounds of definite composition. 

 The Liquor Colds iMccharatiu of pharmacy is a 

 solution of lime in syrup, and with baryta sucrose 

 forms the coni|K>una CHn(BaOH)Oii, which falls 

 as a precipitate when syrup is mixed with a con- 

 centrated solution of barium hydroxide. With 

 strontia sucrose forms the compound CuHjo 

 (SrOH)iOn as a precipitate, and this reaction is 

 employed commercially for the separation of crys- 

 tallisa'ble sugar from molasses. The precipitate is 

 granular, easily separates, and after being washed 

 with hot water is decomposed with carbonic acid. 



Sucrose in the solid condition, or in the form of 

 a strong syrup, is decomposed iji the cold by con- 

 centrated sulphuric acid, with formation of a 

 spongy carbonaceous mass, and evolution of 

 sulphur dioxide and other volatile products. 

 Nitric acid acte upon sucrose, forming nitro- 

 ancrose, saccharic acid, oxalic acid, or carbonic 

 acid, according to the concentration of the nitric 

 acid ; the fuming acid in the cold produces nitro- 

 sucrose. Sucrose, like all the members of the 

 saccharose group, is hydrolysed when heated in 

 solution with dilute acids ; in the case of sucrose 

 a mixture of dextrose and In-vulose results, the 

 change consisting in the assimilation of the ele- 

 ments of water and bisection of the sucrose mole- 

 cule. This action is termed 'inversion,' twaMM 

 the solution after the action of the acid rotates 

 the plane of ]M>larisation to the left, but the term 

 is now applied generally to the hydrolysis of sac- 

 charoses by acid. Inversion takes place slowly 

 even in the cold with hydrochloric or sulphuric 

 acid, and with dilute solutions of sucrose, but at 

 70 C. the change is very rapid ; acetic, tartaric, 

 citric, and the other weak acids have much less 

 jMiwer in this respect. The process of inversion is 

 of value in analysis of mixtures of \ai ions sugars. 



Sucrose is a strong reducing agent, which is 

 another way of saying that it is readily oxidised. 

 It quickly decolorises solutions of potassium 

 permanganate even in the cold, and on Ixiiling 

 with this reagent yields oxalic and carbonic acids. 

 \\ hen heated with solutions of silver or mercury 

 it causes separation of the metals, and it precipi- 

 tate* gold from the chloride. When Imilcd with 

 cupric salts in presence of alkaline hydroxides 



there is no separation of cuprous oxide, but after 

 continued ebullition a partial reaction occurs. 

 After mi. lei-going inversion by dilute acids or 

 imcrtase it quickly and completely reduces alka- 

 line solution-, of copper (see below). 



The iH-haviour of sugar under the influence of 

 living ferments is of great interest theoretically, 

 and of imixirtance from a practical point of view. 

 Some of the mould fungi (Hyphomycctes), nearly 

 all the yeasts (Saccharomycetes), and many torula 

 forms ferment solutions of sugar with formation of 

 alcohol and carbonic acid in presence of some forms 

 of albuinenoid matter, and of certain inorganic 

 substances. The mould fungi, particularly those 

 of the genus Mucor, function as alcoholic ferments, 

 that property being especially but not exclusively 

 possessed by the budding spores of these organisms, 

 which in many instances closely resemble the yeasts 

 in appearance. The commonly occurring mould 

 PentciUium glaucum possesses the power of secret- 

 ing an invcrtive ferment which is able to com, -it, 

 sucrose into other sugars. Jtfonilia Camliiln directly 

 ferments solutions of this sugar without previous 

 inversion, a property not possessed by the strong 

 yeasts ; Mucor racemosus secretes invertase and fer- 

 ments sucrose after inversion ; several <>i her M uc.n s, 

 as M. erectus, M. spinosus, M. mucedo, M. fir--, 

 loiden, \c. , have no inverting action, but can pro- 

 duce fermentation after the sugar has been inverted 

 by extraneous means. But the chief interest attaches 

 to the action of yeast, which are par excellence the 

 true alcoholic ferments. The strong yeasts, ,SW. 

 charomyces cerevisias (both top and bottom forms), 

 the two forms of S. ellipsoideus (liottom foi i 

 and the three forms of a. pastorianus, all secrete 

 invertase and vigorously ferment sucrose, i if the 

 feeble yeasts S. mnrxiatius and S. rsii/inm i Han- 

 son), which have little action on maltose, invert 

 sucrose and ferment it with energy, lit the other 

 species of Saccharomyces in some instances little is 

 known regarding their fermentative action ; but >'. 

 mtmbrantefacietu! is believed to be the only s 

 charomyces which neither inverts nor incites fer- 

 mentation of one kind or another. N. ii/tii-n/i<tu*(Mt 

 called, although not a true Saccharoniycus liecause it 

 forms no gonidia) secretes no invertase, and there- 

 fore cannot act upon sucrose. The. act ion even of tin- 

 stronger yeasts ujxm this saccharose is very feeble 

 in the absence of albumenoids of the peptone class 

 and of the necessary salts, but in the presence of 

 these latter ammonium compounds, asparagin, and 

 some other nitrogenous bodies can toa great extent 

 supply the place of the albumenoids. I'ndt-r favour- 

 able conditions viz. the presence of these necessary 

 yeast foods and of sucrose to an extent not too 

 great the introduction of a small quantity of 

 healthy yeast is quickly followed by the multipli- 

 cation of the organism, accompanied by inversion 

 of the sugar and the production of alcohol and car- 

 bonic acid. The process of inversion takes place 

 at an early stage of the fermentation, and is a 

 chemical reaction capable of In-ing i-lfccted hy the 

 enzyme (invertase), separately presented in the 

 absence of the organism ; the production of alcohol 

 is a function of the living cell, ami becomes slower 

 and more difficult as the percentage of spirit in- 

 creases, the alcohol constantly ten. ling to inhibit 

 the fermentative act, until at length, when about 

 14 per cent, of alcohol has been produced, it ceases 

 altogether. Pasteur, who was the first to show the 

 true character of yeast, formerly considered the 

 fermentation of sugar to be an anaerobic pin 

 in. 'ii. .n. taking place only in the absence of oxygen, 

 in order to obtain which the yeast tears up the 

 sugar molecule ; this view , however, is not now 

 held, it being believed that the Saccharomycetes 

 are to a great extent indifferent in this respect, 

 playing their part equally well in presence oi 



