296 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 



nitrocotton. It is in such a loose state of equilibrium that the slight- 

 est reaction will npset its balance. No wonder that when nitrocellu- 

 lose is mixed with another explosive like nitroglycerin to form smoke- 

 less powder it becomes less reliable, and acts detrimentally on the 

 nitroglycerin. This is accentuated still more in the presence of 

 another disturbing factor, such as heat or an alkali. It is a fact that 

 any alkali, however weak, will gradually saponify the nitrocellulose, 

 and although dangerous decomposition would rarely set in, a bad 

 heat test may result and cause the nitrocellulose to be destroyed by 

 the authorities. Chalk in Avater is no exception to this action. 



The case is very much aggravated by the action of heat. It is 

 Avell known that properly purified guncotton has been stored in all 

 climates Avithout giving rise to alarming decomposition, even when 

 the temperature was above the normal. Nitroglycerin and nitro- 

 cellulose, both of which will by themselves give a potassium iodide 

 heat test of, say, twenty minutes, may, however, when mixed, not 

 stand more than ten minutes. It is a convenient excuse to say that 

 this is due to an alteration of the physical state, but no proofs haA^e 

 been given for such an assertion, and I should be curious to hear of 

 them. 



The amount of nitrous acid required to color the test paper is so 

 small (according to Will" it is only 4 X 10"° milligrams, equivalent 

 to 0.0000016 per cent, or about 1 in 60,000,000 for a sample of 2.5 

 grams) that whatever its physical state, there would ahvays be 

 enough material exposed on the surface to give off this quantity of 

 gas in regulation time if the explosive Avere of a low order of stabil- 

 ity. There is much more justification for supposing that a chemical 

 reaction goes on betAveen the nitroglycerin and nitrocellulose at the 

 elcA^atecl temperature of the heat test (82° C), the nitrocellulose being 

 first decomposed, and the nitrous gases developed reacting on the 

 nitroglycerin and thus accelerating the decomposition. 



We next come to the treatment a poAvder undergoes during manu- 

 facture. Whether passed under steam-heated or high-pressure rolls, 

 Avhether kneaded for hours in a mixing machine, squeezed from a die 

 with an unnecessary amount of pressure and friction, due to a defect 

 in or bad construction of the die, AAdiether it be dried for weeks and 

 months at temperatures far above the normal, everything tends to 

 destroy the equilibrium of the nitrocellulose. Years ago the author 

 showed that there is a critical point for mixtures, such as blasting 

 gelatine or smokeless powders at or about 45° C, yet during manu- 

 facture this temperature is frequently approached and sometimes 

 exceeded. 



°Dr. W. Will, " Untersncbnnfren iiber die Stabilitiit von Nitrocellulose 2. 

 Mitteilung. Der Grenzziistand der Nitrocellulose in quautitativer Bezieliung." 

 Neubabelsberg, 1902, p. 28. 



