194 GRAPE-SUGAR. 



2. Cane-sugar group, C 12 H 22 O n . The bodies of 

 this group are formed by the combination of two 

 molecules of the aldehydes, water being eliminated. 

 They contain eight OH groups, and are readily con- 

 verted into the bodies of the first group by assimila- 

 tion of water. 



3. Cellulose group. The bodies of this group have 

 the composition expressed by the empirical formula 

 C 6 H 10 5 ; most of them, however, appear to have a 

 higher (double or triple) molecular weight. They 

 assimilate water readily, and are thus converted into 

 the aldehydes of the first group. 



1. Grape-Sugar (Glucose). 

 C 6 H i2 6 = CH 2 .OH(CH.OH) 4 .CHO. 



Occurrence. In the juice of grapes, plums, cherries, 

 figs, and other sweet fruits ; in honey ; in the urine of 

 diabetic patients, and in other animal fluids. 



Formation. It is formed, together with fruit, sugar, 

 from cane-sugar by the action of acids or ferments; 

 from starch or cellulose by boiling them with dilute 

 sulphuric acid, or by the action of diastase; from 

 amygdalin, salacin, tannic acid, etc. (See Glucosides.) 



Preparation. The juice of grapes is neutralized with 

 chalk, clarified by the white of eggs, and evaporated 

 to the point of crystallization. 50 parts starch are 

 added gradually to a boiling mixture of 100 parts 

 water and 5 parts sulphuric acid; the starch dis- 

 solves, is at first converted into dextrin, and, after 

 being boiled for several hours, into sugar. The acid is 

 then saturated with calcium carbonate, the saccharine 

 solution filtered from the gypsum, treated with 

 animal charcoal, and evaporated to a syrupy consist- 

 ence. 400 parts water are heated to 60-62 with 8 parts 

 barley malt,* and 100 parts starch stirred into the mix- 

 ture in small portions. The starch is soon dissolved, 

 and, by the action of the diastase in the malt, is coii- 



* Germinated and then thoroughly dried barley. 



