CARBOHYDRATES. 315 



C 6 H 10 5 .H 2 O. Other gums occur in the cherry tree, in linseed 

 or flaxseed, in Irish moss, in marsh-mallow root, etc. 



Cellulose, C 6 H 10 5 , perhaps C 18 H 30 15 (Plant-fibre, Lignine}. Cellu- 

 lose constitutes the fundamental material of which all cells and 

 vessels of vegetables are built up, and forms, therefore, the 

 largest portion of the solid parts of every plant; it is well 

 adapted for this purpose on account of its insolubility in water 

 and most other solvents, its resistance to either alkaline or acid 

 liquids, and its tough and flexible nature. Some parts of vege- 

 tables (cotton, for instance) are nearly pure cellulose. 



Pure cellulose is a white, translucent mass, insoluble in all the 

 common solvents, but soluble in an ammoniacal solution of 

 basic cupric carbonate; it is not colored blue by iodine. 



Treated with concentrated sulphuric acid it swells up, and 

 gradually dissolves; water precipitates from such solutions a 

 substance known as amyloid, which is an altered cellulose giving 

 a blue color with iodine. 



Unsized paper (which is chiefly cellulose) dipped into a 

 mixture of two volumes of sulphuric acid and one volume of 

 water, forms, after being washed and dried, the so-called " parch- 

 ment paper," which possesses all the valuable properties of 

 parchment. 



Pyroxyline, Pyroxylinum, C 6 H 8 (N0 2 ) 2 5 (Dinitro-cellulose, Soluble 

 gun-cotton). By the action of nitric acid of various strengths on 

 cellulose, three different substitution products may be obtained, 

 which are distinguished as mono-, di-, and trinitro-cellulose: 



C 6 H 10 5 + HN0 3 = C 6 H 9 (N0 2 )0 5 + H 2 O. 

 C 6 H ]0 5 + 2HN0 3 = C 6 H 8 (N(V 2 5 -f 2H 2 O. 

 C.H 10 5 + 3HN0 3 = C 6 H 7 (N0 2 ) 3 5 + 3H 2 0. 



The trinitro-cellulose is the highly explosive gun-cotton; the 

 dinitro-cellulose or pyroxyline is soluble in a mixture of ether 

 and alcohol; this solution is known as collodion. 



Pyroxyline is best made by immersing cotton for 10 hours in 

 a cooled mixture of 6 parts of sulphuric acid and 5 parts of 

 nitric acid, and washing it with cold water until the washings 

 no longer show an acid reaction. Xeither the mono- nor tri- 

 nitro-cellulose is soluble in a mixture of ether and alcohol. 



