538 Dr. R. Hare on the Explosiveness of Nitre, 



statu quo, The difference in degrees caused in the height of 

 the barometric column, divided by two, gave the number of 

 cubic inches of gaseous matter evolved. This difference was 

 of course set down. 



28. In the next place, the temperature being carefully ob- 

 served and recorded, about 2 cubic inches of a strong solu- 

 tion of caustic potash were added. The consequent absorption, 

 as it declined in rapidity, was assisted by an agitation conse- 

 quent to moving up and down the rod, and the perforated 

 disc attached to it. When no more absorption could be ob- 

 served to take place, judging by the quiescence of the mercu- 

 rial column in the gauge, and when the temperature had re- 

 turned to the starting-point from which it had been disturbed 

 by the heat generated through the reaction between the alkali 

 and carbonic acid, the height of the column was again re- 

 corded, and the difference of degrees, divided by two, was 

 estimated to give the number of cubic inches of carbonic acid 

 generated. Allowance was made for the mechanical effect of 

 the bulk of the alkaline liquid in lowering the mercurial 

 column founded on actual measurement of the effect of a like 

 quantity of water ; the mercury being brought to the same 

 height in the gauge-tube, in an experiment made for the pur- 

 pose with atmospheric air. 



29. Three samples of Dupont's powder were obtained from 

 the United States Arsenal, severally designated cannon, 

 musket, and rifle powder. Of each, 75 grains were pressed 

 into an indurated cylindrical mass, as above described, and 

 successively burned in the exhausted receiver. 



The following are the results : — 



Cannon powder, gas evolved . . . 55 cubic inches. 



... absorbed . . 23^ 



Musket powder ... evolved ... 52 



... absorbed . . 21i 



Rifle powder ... evolved . . . 51 \ 



... absorbed . . . 20| 



Sporting powder, average of two experiments, — 



Gas evolved 51 cubic inches. 



... absorbed . 25 



30. As the gas left after the removal of the carbonic acid 

 had all the negative characteristics of nitrogen, it may be 

 concluded from the results above given, that the gaseous pro- 

 ducts of deflagrated gunpowder consist of nearly equal volumes 

 of carbonic acid and nitrogen. 



31. I was naturally led to compare the results of the defla- 

 gration of gun-cotton with those of gunpowder. Accordingly, 

 I exposed a tuft of gun-cotton, weighing 25 grains, in the 



