1894.] Researches on Modern Explosives. 13 



The other branch of the three-way tap was connected with a 

 separate drying apparatus. When the water surrounding the bomb 

 was boiling, by starting the vacuum pump the steam and water were 

 drawn into the absorbing apparatus ; after a good vacuum had been 

 made in the bomb the three-way tap was turned so that dry air 

 rushed in, then connexion was made with the drying apparatus, the 

 bomb again exhausted, and so on, alternately, until (as experience 

 showed) all the water had been removed from the bomb and collected 

 in the drying tubes, which were then weighed. The weights of water 

 thus obtained were calculated for comparison into volumes of H 2 

 gas at C. and 760 mm. 



The analyses of gas were carried out in duplicate in Dittmar's 

 apparatus as improved by Lennox. 



In most of the experiments the bomb, previous to firing, was ex- 

 hausted, and the amount of residual pressure, varying from 24 to 

 40 mm., noted on closing it. The amount of air corresponding to 

 these pressures left in the bomb has the effect of increasing the heat 

 generated by a small quantity amounting to 5 to 7 calories. This 

 quantity being within the limits of error of the calorimetric observa- 

 tion no correction was made for the same, but the quantity of 

 residual air was taken into account when comparing the weights of 

 the products found with the weight of the explosive used. Thus in 

 Tables I and II the volumes of gas of the given composition and 

 of aqueous vapour were obtained from the given weight of ex- 

 plosive increased by the weight of the air corresponding to the 

 vacuum indicated. 



When firing in an exhausted bomb it was found necessary to have 

 the explosive surrounding the firing wire in comparatively small 

 pieces in order to ensure ignition of the whole charge. 



Table I gives the principal results obtained with the several 

 gunpowders above mentioned, Tables II and III give the results 

 obtained with samples of ballistite made with different proportions 

 of the component parts, Table IV indicates the effect of firing 

 different weights of the same explosive in a closed vessel from which 

 the air has not been exhausted, and Table V gives the original elemen- 

 tary composition of several explosives compared with the products of 

 combustion, both being represented as weights. 



With the exception of the results given in Table IV, all the others 

 were obtained from the firing of 4 grams of the explosive. 



In Tables I and II we have expressed the results of firing some 

 powders now in use as well as certain specially prepared powders, so 

 as to show the quantity of heat and the volumes and analyses of 

 the gases produced, and have in the column headed " Coefficient of 

 potential energy," given figures which serve as a measure of com- 

 parison of the power of the several explosives. These figures are 



