280 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1908. ' 



complete, the centrifugal is set in motion and the acid wrung out. In 

 other words, the removal of the nitrocotton and nitrating acids from 

 the pots into the centrifugal machines is avoided. I am perhaps an 

 heretic, but I have never been able to see the advantage of these nitrat- 

 ing centrifugal machines. They cost a great deal of mone}^ ; they are 

 liable to get out of order ; one can only nitrate about 8 kilograms of 

 cotton in each, and with a nitrating period of, say, half an hour, one 

 can at the best make 10 charges a day in each ; further, if the nitrating 

 time is an hour, the number of nitrations is about 7 only. This 

 means that for a fairly large production one requires a large number 

 of centrifugals, and it is easy to calculate what this would mean in an 

 artificial silk factory producing, say, 3 tons of nitrocellulose per day. 

 The quantity of acid used for nitration must be greater, because the 

 space between the basket containing the cotton and the jacket of the 

 machine has to be filled up with acid, and similarly there are a good 

 many other disadvantages. There is no difficulty in arranging pots 

 or basins in such a way that the fumes arising from them are led away 

 by means of an earthenware fan into an absorbing tower, just as is 

 done in nitrating centrifugals and discharging these nitrating vessels 

 into a wringing machine without its being necessary to expose the 

 workmen to fumes or spilt acid. Such factories have been working 

 very manj^ years and give every satisfaction. 



Since there is an excess of waste acid produced in revivification, 

 this waste acid is sometimes denitrated in the same way as the acid 

 from nitroglycerin manufacture, but may more advantageously be 

 used in manufacturing fresh nitric acid, because in this case the nitric 

 acid contained in the waste acid is recovered as pure monohydrate. 



Revivification is nowadays very frequently carried out with sul- 

 phuric acid containing 20 per cent of suliDhuric anhydride (oleum). 



When the gun cotton is pulped and finished it is frequently packed 

 and pressed into boxes. Gun cotton can become moldy on the out- 

 side through fungi and, according to v. Forster, have its structure 

 destroyed ; °' and v. F()rster found this was promoted by paper in the 

 cases, whilst Malenkowicz ^ showed this to be due to moisture acting 

 on the wood of the boxes. It is very important to select proper pack- 

 ing material on account of the possibility of detrimentally influencing 

 the stability. 



A new process for the nitration of cotton is due to Messrs. James 

 Milne Thomson and William Thomson, of Waltham Abbey," and it 

 has already been introduced in some factories. An earthenware fun- 

 nel-shaped vessel can be connected at its stem by means of cocks, 



"- Max V. Forster, " Versnche niit compriniirter Sehiessbaumwolle," r>erlin. 

 1883, p. 11. 



^ '' Mittheilnngen fiber GegenstJliKle des Artillerieweseus," 1907, p. 599. 

 <' British patent No. 8278, of 1903. 



