752 SACCHARINE SUBSTANCES. 



Hydrated saccharic field . . C 12 H 5 O n 



TCO 

 Acid saccharate of potash . C 12 H 5 O n 



Saccliarate of ammonia . . . CHO n 



First saccharate of lead . . CHO 



Saccharate of zinc . . . . CHO 



Second saccharate of lead . . CHO 



Third saccharate of lead . . C 12 H 5 O n + 5PbO 



It is remarkable that hydrated saccharic acid contains the 

 elements of 2 atoms of mucic acid ; C 12 H 10 O 16 =2 (C 6 H 5 Og) ; 

 a substance produced by the same mode of oxidation of milk 



sugar.* 



GRAPE SUGAR. 



Syn. Starch sugar, diabetic sugar, the sugar of fruits, glucose 

 (Dumas). The formula of crystallised grape sugar is C 12 H 14 O 14 , 

 but at 212 it fuses and loses 2 atoms of water. This is the 

 sweet principle of raisins, figs, and of most acid fruits ; it exists 

 also in honey, and is the sugar of diabetic urine. It is also a 

 product of the decomposition or transformation of several other 

 substances, as of cane sugar, starch, lignin and milk sugar, when 

 treated with dilute acids. Grape sugar is not so soluble in cold 

 water as cane sugar, and about 2i times less sweet. 



It isobtainedfrom the grape, by neutralising the expressed juice 

 with chalk, clarifying with white of egg, evaporating and setting 

 aside to crystallize. From the urine of diabetes, by evaporating 

 the latter to dryness in a water-bath, washing the dark crystal- 

 line mass on a filter with cold alcohol, and submitting the white 

 residue, dissolved in water, to repeated crystallizations. But 

 this sugar is most largely prepared from starch, and indeed, 

 forms a considerable article of commerce. One part of potato 

 starch is boiled with from l-100th to l-10th of its weight of 

 sulphuric acid and four parts of water, for thirty-six or forty 

 hours, the water being replaced as it evaporates. The solution 



* Thaulow, sur 1'Acide Saccharique, An; de Chiraie, &c. Ixix, 52. 



