CANE SUGAR. 747 



by Mr. E. A. Parnell, when dried at 212, to consist of 

 C 24 H 21 O 21 . Two compounds which it forms with oxide of 

 lead are thus constituted, C 24 H 21 O 21 + 5PbO, and C 24 I1 18 O 18 

 + 3PbO.* 



Lichen starch. Several species of lichens, particularly the 

 Cetraria Islandica (Iceland moss), contain a variety of starch, 

 closely resembling common starch. It gives a white and opaque 

 jelly. It is feebly coloured by iodine, the tint produced being 

 between brown and green. This starch contains, according to 

 the analysis of Guerin-Vary, C 10 H n O 10 , but this result re- 

 quires confirmation, 



SUGARS. 



Several substances are known as sugars which agree in having 

 a sweet taste, but differ in other respects. Those which un- 

 dergo a peculiar decomposition and are converted into carbonic 

 acid and alcohol, when their solution is mixed with yeast, are 

 fermentable sugars, and form the most important class ; they 

 are Cane sugar, Grape and Starch sugar, which appear to be 

 identical, Milk sugar, Mushroom sugar, and the insipid sugar 

 of Thenard, of which the two first-mentioned varieties are the 

 most abundant and best understood. 



CANE SUGAR, OR ORDINARY SUGAR, 



Its formula in the crystallised state is C 12 H n O n ; in com- 

 bination with oxide of lead, C 12 H 9 O 9 + 2PbO (Peligot). 



Loaf sugar, sugar-candy, or the purest granular muscovado 

 may be taken to represent this species. It exists in many 

 plants, but is derived in large quantity only from the juice of 

 the sugar-cane, from beet-root and the maple-tree. These 

 juices are rapidly evaporated with a small addition of lime, to 

 neutralise free acid, being sometimes clarified first by albumen, 

 and afford on cooling a brown granular sugar, from which a 

 dark coloured syrup, molasses, separates. The latter contains 

 a portion of crystallizable sugar, which may be separated from 

 it by evaporation, and leaves treacle, which differs in taste from 

 crystallizable sugar, and is certainly a distinct species of sugar, 

 although highly impure. To refine sugar, it is dissolved in 



* Phil. Mag. 3rd series, vol. 17, p. 126. 



