398 INCANDESCENT MANTLES. 



One of the nio.st reiiuii kable developments of the last fifty ^^ears has 

 been the wonderful way in which the lower form of gun cotton, known 

 as collodion cotton, has l)een utilized for commercial purposes, and at 

 the present time it bids fair to invade the territory of incandescent 

 mantle making-. It was in 1838 that the chemist Pelouze drew atten- 

 tion to the fact that when paper was acted upon by the strongest nitric 

 acid it increased in weight and acquired the property of burning with 

 enormous rapidity, while as early as 1S82 Braconnot had prepared a 

 substance called ""xyloidin" by acting upon starch, linen, and sawdust 

 iri the same way. It was not, however, until 1S45 that any serious 

 attention was directed to the use of such su))stances as explosives, 

 when Schonbein first called attention to nitrated cotton wool and advo- 

 cated its use as a substitute^ for gunpowdor, showing that in explosive 

 energy it was far superior to it. 



Experiments were at once instituted on a large scale and its manu- 

 facture carried on in Kngland and also on the Continent, but in lS-t7 

 a very serious cxpiosioM occurred at the works in which it was maiui- 

 factured l)y the Messrs. Hail, at Faversham, while a year later an 

 even more serious ex])losion followed in the gun-cotton factory at 

 Bouchet, near Paris, and as no reason could l)e assigned for these and 

 other similar explosions, gun cotton was lookinl upon as too danger- 

 ous an explosive for ordinary use. and its maiuifacture was for a time 

 discontinued. 



During this brief period, however, it had been discovered that if 

 the strength of the nitric acid emi)loyed in the manufacture were 

 slightly reduced, a compound was formed which had the property of 

 dissolving in a mixtui-e of alcohol and ether, which was not the case 

 with the true gun cotton, and that on allowing the solvent to evaporate, 

 a semitransparent mass was left in which no trace of the structure of 

 the original material remained. This solution was eminently adapted 

 for forming thin films on glass plates, and as this was a great desid- 

 eratum at this particular period for photographic purposes, the new 

 material began to ])e manufactured on a fairly large scale. It was 

 soon found that by slight modifications in the method of manufacture 

 and by loading it with various foreign materials, excellent imitations 

 of amber, ivorj^, and tortoise shell could be obtained, with the result 

 that the manufacture of collodion has now attained considerable 

 importance. 



One of the most beautiful applications of collodion is the manufac- 

 ture from it of artificial silk. In the interesting but little-known 

 town of Besanfon, the French inventor Chardonet has established a 

 manufactory in which collodion made by nitrating wood pulp is dis- 

 solved in the smallest possible quantity of alcohol and ether, and the 

 emulsion is then squeezed out under a pressure of 750 pounds to the 

 square inch through capillary glass tubes, the clear way of which is 



