LIGNIN, OR CELLULOSE. 81 



means of coagulating albumen. The uncrystallizable portion is 

 named molasses. 



Grape sugar, C^^Jd^, exists in many vegetable juices, especially 

 in grapes. Examples of it are seen in candied sweetmeats, and in 

 raisins ; it also occurs in the urine in diabetes. Grape sugar differs 

 from cane sugar in several particulars : it is less sweet, less soluble, 

 and does not form such regular crystals. Strong mineral acids 

 have but little effect on grape sugar ; the alkalies, on the contrary, 

 produce a decided effect. 



Sugar of milk, lactine, C^O^H^ ;— this is the sweet principle of 

 milk : it is procured by evaporating whey. It undergoes fermenta- 

 tion, like other sugars, but is believed to be converted into grape 

 sugar in the process. 



Mannite or Manna sugar CgHyOg; — this differs from other sugars 

 in not undergoing the vinous fermentation. There is also a sugar 

 from mushrooms and liquorice. 



FECULA, OR STARCH. 



A very abundant proximate vegetable principle, abounding in roots, 

 stems, and seeds. It is procured from flour or potatoes by the action 

 of a stream of water upon them so as to wash of the insoluble par- 

 ticles of fecula. 



Prop. — Insoluble in cold water, alcohol, or ether ; appears to be 

 a homogeneous substance, but if examined by the microscope, it is 

 found to consist of granules, having a thin insoluble envelope ; when 

 starch is put into hot water, the envelope bursts, liberating the con- 

 tents, which form with the water a gelatinous mass. The most 

 delicate test for starch is iodine, which forms with it a blue colour. 



The size of the granules of fecula varies very much, according to 

 the source from which it is derived. Arrow-root, sago, and tapioca, 

 are examples of pure fecula. 



In the process of the germination of seeds, and of the fermentation 

 of malt, the starchy matter of the grain is converted into a sweetish, 

 gummy matter, called dextrine, and ultimately into grape sugar. 

 The cause of this remarkable change is due to a peculiar principle 

 found resident in the grain at that period, named t^zastose, which 

 acts by catalysis, — itself undergoing no change. 



Dextrine has the same composition as starch. It is used in the 

 arts as a substitute for gum. Sulphuric acid also has the power of 

 converting starch into sugar. Nitric acid converts it into oxalic 

 acid. 



LIGNIN, OR CELLULOSE. 



This constitutes the basis of vegetables and of wood. It is pro- 

 cured from sawdust by dissolving it successively in water, alcohol, 

 ether, dilute acid, and an alkaline solution. It has no taste, but may 



