50 PHYSIOLOGICAL CHEMISTRY. 



Ex. Prepare Schweitzer's reagent by first precipitating copper hydrox- 

 ide from copper sulphate solution, in the presence of a little ammonium 

 chloride, by addition of sodium hydroxide in excess. Wash the precipi- 

 tate thoroughly and then dissolve it in the smallest possible quantity of 

 strong ammonia water. This yields a deep blue solution, the reagent in 

 question. It dissolves cotton rather easily. This solution may be filtered 

 after dilution, and from the filtrate a pure cellulose is thrown down by 

 addition of acids. 



By action of strong nitric acid, aided by sulphuric acid, cellulose is con- 

 verted into a series of nitrates or " nitro-celluloses." The number of NO 3 

 groups added depends on the strength of the acid mixture and time of its 

 action. The more highly nitrated products constitute the well-known ex- 

 plosives. Products not so highly nitrated are used in the preparation of 

 collodion and celluloid. This latter is essentially a mixture of camphor 

 and nitrated cellulose from cotton or paper. These bodies are esters and 

 therefore may be decomposed by alkalies. 



x \Mevs\ty of Ca,'/f n 

 *^**O % 







