44 HOW CROPS GROW. 



to a coarse powder by machinery, thon heated with a weak soda lye, 

 and finally bleached with chloride of lime. 



Though cellulose is insoluble in, or but slightly affected 

 by, weak or dilute acids -and alkalies, it is altered and dis- 

 solved by these agents, when they are concentrated or 

 hot. The result of the action of strong acids and alka- 

 lies is various, according to their kind and the degree of 

 strength in which they are employed. 



Cellulose Nitrates. Strong nitric acid transforms 

 cellulose into various cellulose nitrates according to its 

 concentration. In these bodies portions of the hydrogen 

 and oxygen of cellulose are replaced by the atomic group 

 (radicle), N0 3 . Cellulose hexanitrate, C 12 H 14 (X0 3 ) 6 0i , 

 is employed as an explosive under the name gun cotton. 

 The collodion employed in photography is a solution 

 in ether of the penta- and tetranitrates, C ] 2H 15 (N03) 5 1 o 

 and C 12 H 16 (N0 3 )40 10 . Sodium hydroxide changes these 

 cellulose nitrates into cellulose and sodium nitrate. 



Hot nitric acid of ordinary strength destroys cellulose 

 by oxidizing it with final formation of carbon dioxide 

 gas and oxalic acid. 



Cellulose Sulphates. When cold sulphuric acid 

 acts on cellulose the latter may either remain apparently 

 unaltered or swell up to a pasty mass, or finally dissolve 

 to a clear liquid, according to the strength of the acid, 

 the time of its action, and the quality (density) of the 

 cellulose. In excess of strong oil of vitriol, cellulose 

 (cotton) gradually dissolves with formation of various 

 cellulose sulphates, in which OH groups of the cellulose 

 are replaced by S0 4 of sulphuric acid. These sulphcites 

 are soluble in water and alcohol, and when boiled with 

 water easily decompose, reproducing sulphuric acid, but 

 not cellulose. Instead of the latter, dextrin and dextrose 

 (grape sugar) appear. 



Soluble Cellulose, or Amyloid. In a cooled mix- 

 ture of oil of vitriol, with about its volume of water, 



