COMMERCIAL CELLULOSE PRODUCTS 161 



produced. In the preparation of inferior quality papers there 

 is no chemical treatment of the disintegrated wood pulp ; the 

 material is, therefore, known as mechanical pulp, and paper 

 made from it gives reactions for lignocellulose. Cellulose 

 used for the preparation of filter "papers is, after the ordinary 

 methods of purification, treated with hydrofluoric acid to re- 

 move silica. 

 i 



COMMERCIALLY VALUABLE DERIVATIVES OF CELLULOSE. 



When heated in a concentrated solution of zinc chloride, 

 cellulose is converted into a viscid syrup. This syrup, when 

 forced through glass nozzles into alcohol, forms threads which, 

 after being washed and carbonized, become hard and are 

 used for electric lamp filaments ; they have also been employed 

 for the basis of incandescent lamp mantles. 



Gun Cotton or Pyroxylin. That a variety of different pro- 

 ducts may be obtained by the action of various strengths of 

 nitric acid, either alone or in the presence of sulphuric acid, on 

 cellulose, has already been mentioned. The substance known 

 as gun cotton is a hexanitrate ; it is obtained by immersing 

 dry cotton waste, freed from grease by treatment with alkali, 

 in a mixture of I part nitric acid (sp. gr. 1*52) with 3 

 parts sulphuric acid (sp. gr. I -84) ; the resulting substance is 

 then rapidly and thoroughly washed with water, moulded into 

 discs, and dried on heated plates. On explosion it produces 

 corrosive gases and therefore is not suitable for use, as such, 

 in firearms; when, however, the gun cotton is dissolved in 

 ethyl acetate or acetone and the solution is evaporated, a new 

 substance is obtained which has the same composition as gun 

 cotton, but different properties ; it explodes with less violence 

 and produces no corrosive vapours, and is therefore employed 

 in the manufacture of smokeless powder. 



Blasting Gelatine is a mixture of gun cotton and nitro- 

 glycerine. Gun cotton mixed with a variety of other sub- 

 stances enters into the composition of numerous explosives, 

 such as ballastite, melanite, cordite, etc. etc. 



Collodion is the name applied to a solution of cellulose tri- 

 and tetra-nitrates in a mixture of equal parts of 95 per cent 

 alcohol and ether. 



