GRAPE SUGAR. 



ceases to be gelatinous, and passes first into dextrin and then 

 into sugar. Under some pressure, and at a higher temperature, 

 the change is effected more quickly and by means of a less 

 quantity of acid. A small quantity of oxalic acid -&* may be 

 substituted with advantage in this process instead of the 

 sulphuric acid. The acid is afterwards neutralised with chalk, 

 the solution filtered from the insoluble salt of lime, and evapo- 

 rated to a syrup, which solidifies as a crystalline sugar. Starch 

 is also converted into sugar by means of diastase. Eight 

 parts of ground malt are infused at 158 (70 centigrade) in 400 

 parts of water, and then mixed with 100 parts of starch, which 

 soon dissolves, and by continued digestion at the same tempe- 

 rature is entirely changed into sugar. By calculation, 100 parts 

 of fecula, combining with the elements of four atoms of water, 

 should produce 122.03 parts of crystallized grape sugar ; De 

 Saussure obtained 110 parts, and Brunner from 104 to 106 

 parts. In the transformation of starch into sugar, a variable 

 quality of mannite is always formed at the same time, according 

 to the observations of Fremy. 



To prepare grape sugar from lignin or woody fibre, 12 parts 

 of wood shavings or shreds of paper are gradually mixed with 

 5 parts of oil of vitriol diluted with 1 part of water, care being 

 taken to avoid any rise of temperature ; after twenty-four hours' 

 digestion, the pitchy mass is dissolved in much water, and 

 boiled for ten hours, and the acid afterwards separated as in the 

 former process for sugar from starch. 



Grape sugar does not crystallize so distinctly as cane sugar, 

 but is obtained from its alcoholic solution in square tables or 

 cubes, which are hard and transparent. It is soluble in 1 i parts 

 of cold water, and in all proportions of hot water. It dissolves 

 less rapidly than cane sugar, and gives a more fluid syrup. In 

 alcohol, at a low temperature, it is very sparingly soluble, but 

 at 77 (25 cent.) it is soluble in 8 parts of alcohol of 85 per 

 cent and in 20 parts of absolute alcohol. It fuses with loss of 

 water at 212, and is converted into caramel when not heated 

 above 284 (140 cent.). 



The chemical action of acids and alkalies upon grape and cane 

 sugars are essentially different. Grape sugar dissolves in con- 

 centrated sulphuric acid, colouring it slightly yellow or brown, 

 and forms a compound with it, the sulphosaccharic acid, while 



2 D D 



