PROGEESS IN EXPLOSIVES — GUTTMANN. 279 



ity of factories to produce soluble nitrocellulose by taking equal jDarts 

 of nitric acid of 75 per cent monohydrate and sulphuric acid of 96 

 per cent monohydrate and nitrating the cotton at a temperature of 

 40° C. This nitrating acid therefore contains 1-1.5 per cent of Avater. 

 Yet by merely altering the proportions of acid it is quite possible to 

 make very good soluble nitrocellulose in the cold, and some modern 

 factories nmke it in this way. It seems to be very difficult, if not im- 

 possible, to obtain good and stable completely insoluble nitrocellulose 

 from wood pulp. 



It is now recognized on all sides that there are no definite stages of 

 nitration in nitrocellulose, but that the change in composition goes on 

 without a break, if the conditions are suitable. The manufacturer of 

 gun cotton and nitrocellulose is face to face with great difficulties. 

 Almost ever3'thing he does tends to act detrimentally. From the 

 nitration his nitrocellulose contains a number of lower nitro com- 

 pounds, nitrated oxycellulose and hydrocellulose, nitrosaccharoses, 

 etc., which he has to get rid of. The usual way to do this is to boil the 

 nitro cotton for a long time. It is not quite clear why one should keep 

 on boiling the long and closed-up fibers of unpulped gun cotton for, 

 say, fift}^ hours, as is done in some factories. One would imagine that 

 if after a preliminary washing or boiling the gun cotton were pulped 

 and then boiled this could be done much quicker. As a matter of fact, 

 I have found that by heating the gun cotton whilst pulping the in- 

 crease in stability is very much accelerated, and several factories use 

 the method with advantage. In France they boil for one hundred 

 hours, and I have quite lately seen nitrocellulose that was boiled for 

 two hundred hours without, however, being much the better for it. 

 It must, however, be mentioned that the Waltham Abbey gun cotton 

 as at present made is a very stable and good gun cotton, as judged 

 both by the iodide test and by the destructive test, of which more will 

 be said later on. This is due, in the first instance, to an investigation 

 carried out b}^ Doctor Robertson. He showed that the former method 

 of giving short boilings of two hours and following them up with 

 long boilings of eight and twelve hours was erroneous, and that two 

 long boilings of twelve hours each would liberate acid from the nitro- 

 cellulose, giving an acid water which hydrolizes all the impurities 

 without attacking the gun cotton itself, and that subsequent short 

 washings are useful in eliminating the products of hydrolysis. 

 Having had frequent occasion to put Doctor Robertson's principles to 

 a practical test, I consider it to be one of the most useful pieces of 

 work accomplished since the invention of gun cotton. 



Messrs. Selwig and Lange. of Braunschweig, have invented the so- 

 called " nitrating centrifugal machine," wherein the cotton is dipped 

 and allowed to stand for the requisite time, and, the nitration being 

 S8292— SM 1908 19 



