PEOGEESS IN EXPLOSIVES GUTTMANN. 297 



In some countries the heat test is still carried out at a temperature 

 of 65° C, and if the exphjsive stands it for, say, thirty minutes, the 

 result is considered satisfactory. Yet how often have we seen this 

 temperature attained during manufacturing operations, and main- 

 tained for hours! Is this reasonable? 



We will assume now that we have taken every precaution to manu- 

 facture an explosive which, as regards purity of its ingredients 

 and as regards care in its preparation, leaves nothing to be desired. 

 We were told everyvrhere until about ten j^ears ago, and are still told 

 so in this country, that the explosive must be heated to a temperature 

 varying from 05° to 82° C. without developing sufficient nitrous acid 

 fumes within, say, ten minutes to color potassium iodide paper. The 

 vagaries of this test are very amusing. Eleven years ago '^ the autlior 

 was the first to show how it could be masked and falsified. Tlie 

 potassium iodide paper itself is an uncertain factor. Great jjrecau- 

 tions must be taken in its preparation, while the thickness of the 

 paper is such a disturbing factor that the paj^ers from one official 

 source give a test nearly double those from another. 



Various other tests on similar lines have been proposed to replace 

 the potassium iodide test, but not one of them is a true test of stabil- 

 ity. The potassium iodide, or the diphenylamine test, if always car- 

 ried out under identical conditions, are good enough as a rough check 

 on the manufacture. They do not, however, show v.hether the ma- 

 terial itself is so constituted as to remain stable. This is, perhaps, of 

 small importance in the case of nitroglycerin or an aromatic nitro- 

 compound with their relatively simple structure, but it is all im- 

 portant for nitrocellulose, where the heat test in the opinion of most 

 experts is of little value as a criterion of the finished article. In order 

 to judge of stability, the critical point at which an explosive breaks 

 down must be found, and it is also necessary to determine whether 

 decomposition proceeds regularly or at a dangerous and increasing 

 rate when this point is passed. A number of tests have been proposed 

 to fulfill these conditions. They are all based on the principle that 

 a small quantity of exj^losive is heated to a temperature which causes 

 decomposition comparatively quickly yet gives sufficient time to dif- 

 ferentiate results. In France this temperature was 110° C., but all 

 the modern so-called " destruction " tests are made between 130° and 

 135° C. 



All these tests require a considerable amount of time and constant 

 supervision by a chemist. A rapid and reliable method is to heat 

 the explosive in long glass tubes immersed in a bath of amyl alcohol 

 provided with a reflux condenser, and to note the time that elapses 



« The Chemical Stability of Niti'o-compound Explosives, " Journal of the 

 Society of Chemical Industry," April 30, 1897. 



