334 CHEMISTEY. 



down considerably, and then cooling it. This sugar is so 

 hard as to appear gritty when crushed between the teeth, 

 and is both less soluble and less sweet than cane-sugar. In 

 Switzerland and some other countries, where great quanti- 

 ties of cheese are made, there is some trade in this sugar ; 

 but very little of it is sold in the markets of the world in 

 comparison with other kinds of sugar. Milk-sugar is used 

 in pharmacy. 



460. Grape-Sugar. This is by no means as sweet as cane- 

 sugar, as you can readily see by comparing the taste of a 

 candied raisin with that of common sugar. A gramme of 

 common sugar has as much sweetening power as two and 

 a half grammes of grape-sugar. Cane-sugar is also twice 

 as soluble in water as grape-sugar, consequently the sirup 

 made with cane-sugar has a more tenacious consistency. 

 Their difference in composition may be shown thus: 



Two molecules of One molecule of One molecule of 



glucose. sucrose. water. 



2(C 6 H 12 6 ) =' C i2 H 22 O u + H a O 



461. Sugar made from Starch and Wood. Grape-sugar 

 can be made from either starch or wood by the agency of 

 heat and sulphuric acid. You saw in 454 that sulphuric 

 acid with a certain degree of heat converts starch into the 

 gum called dextrin. Now with a higher degree of heat 

 you can make it convert the starch into sugar. Bring to 

 brisk boiling five tablespoonfuls of water, in which are 

 twenty drops of sulphuric acid, and add gradually thirty 

 grammes of starch made into a paste, keeping the water all 

 the while boiling. Let the boiling continue about half an 

 hour, and the requisite change is effected you have a 

 sirup, that is, sugar dissolved in water. But the sulphuric 

 acid, which is not at all changed in the operation, is in the 

 sirup. This you can get rid of in the way described in 

 454, and then on evaporating the sirup you have the 



