142 THE CARBOHYDRATES 



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 

 recently 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. i'52) with 3 

 parts sulphuric acid (sp. gr. r84); 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. 



A substance known as artificial india-rubber* is produced 

 by kneading together a mixture of tri- and tetra-nitrocelluloses 

 partially dissolved in ether alcohol with castor oil. The 

 resulting substance may be made to have any degree of elas- 

 ticity, according to the materials which are mixed with it. 

 It forms a more or less satisfactory substitute for rubber and 

 possesses a high electric resistance. Though not explosive, it 

 is inflammable, but to do away with this inconvenience the 



* This substance must be carefully distinguished from so-called Synthetic 

 rubber, which is an artificially synthesized hydrocarbon of the formula (C^Hg)" ; 

 this substance, if not actually identical with natural rubber, is at any rate closely 

 related to it, whereas the artificial india-rubber mentioned above is a nitrated 

 cellulose. 



