88 MATTHEW HAY AND ORME MASSON ON THE 



obtained from various sources. He used different methods and got results 

 varying from 137 to 16*6 per cent., the percentage required by the formula of 

 glyceryl tri-nitrate being 18*5. From this he concluded that commercial nitro- 

 glycerine contains the mono- and di-nitrate, as well as the tri-nitrate. 



Beckerhinn,* in 1876, described an extremely elaborate method for the 

 estimation of the carbon and hydrogen, but gave no results. 



Hess and ScHWAB,t in 1877-78, made some nitrogen determinations by 

 Dumas's method. In one sample they found 15*72 and 15*65 per cent., and in 

 another (from Nobel's Zamky manufacture of 1872) they found 16*13, 1612, 

 and 16*12 per cent., though this was the same liquid which four years earlier 

 had yielded Hess only 14*0 per cent. 



Sauer and Ador,| in 1877, estimated by three methods the nitrogen in nitro- 

 glycerine obtained from dynamite. First they used Reichardt's modification 

 of Schloesing's method, after decomposing the liquid with potash, and obtained 

 from 12*3 to 14 per cent. Next they tried the ignition with soda-lime process, 

 but found that only 2 to 3 per cent, of the nitrogen was evolved as ammonia. 

 Finally they made four determinations by Dumas's method, using nitroglycerine 

 obtained from three different samples of dynamite ; and in this case they 

 obtained from 18*35 to 18*52 per cent., which agrees very closely with the per- 

 centage calculated from the formula, but differs widely from that obtained by 

 Hess and Schwab by the same method. 



The nitroglycerine which we employed in our analyses was made by adding, 

 drop by drop, one part by weight of Price's pure glycerine to a mixture of two 

 parts of nitric acid (sp. gr. 1*49) and six parts of sulphuric acid (sp. gr. 1*84), 

 the mixture being surrounded with ice and kept at a temperature never 

 exceeding 10° C. Five minutes were allowed to elapse before pouring the 

 mixture into water ; and the precipitated nitroglycerine was then well washed 

 eight times with large volumes of distilled water, and dried for seven hours in 

 an air-bath at a temperature of from 70° to 80° C. Finally, it was allowed to 

 stand twelve days over sulphuric acid in the exhausted receiver of an air-pump. 

 Not the slightest sign of decomposition ensued ; and it was found that the 

 nitroglycerine, after standing one week in vacuo, had lost less than one-tenth 

 per cent, of its weight, which shows that it was practically dry from the first. 

 It was perfectly colourless and transparent. Its specific gravity at 14°*5C. 

 was 1*601. 



The carbon and hydrogen were estimated by ignition in a tube closed and 

 drawn out at one end and filled with copper oxide and metallic copper in the 

 usual manner. At the termination of the ignition the drawn-out point was 



* Beckerhinn, Sitzgsber. Wien. Akad., Bd. lxxiii., Abth. ii. S. 240. 

 t Hess u. Schwab, Ber. Deutsch. chem. Gesellschft., Bd. xi. S. 192. 

 % Sauer u. Ador, Ibid., Bd. x. S. 1982. 



