1879.] 



Researches on Explosives. 



133 



those occurring when small quantities are fired under feeble tensions, 

 the original explosion-apparatus was designedly adopted in the earlier 

 stages of these experiments, so as to determine the heat generated 

 when gunpowder is fired under high tensions, for which purpose 

 vessels of great strength and weight, and therefore not well suited for 

 calorimetric observations, were indispensable. 



A further investigation of this branch of the subject has shown, 

 however, that the difference between the authors' earlier determina- 

 tions of heat and those of other experimenters referred to by MM. 

 Morin and Berthelot are due, not to errors in the former, but to 

 essential differences in the decomposition of different descriptions of 

 powder. 



In continuing their heat experiments the authors made use of two 

 explosion-vessels, similar in general form to the larger vessel described 

 in the first memoir, but of small capacity and weight.* The specific 

 heats of both these vessels were carefully determined, and the amount 

 of heat absorbed by the calorimeter for various changes of temperature 

 was also carefully determined. Thermometers specially made for the 

 purpose, and capable of being read to 0°'01 F. ('006 C), were used in 

 these experiments. 



To determine the heat generated, a charge of from 150 to 200 grs. 

 (9*72 to 1296 grms.) in the smaller cylinder, of 400 grs. (25"92 grins.) 

 in the larger cylinder was carefully weighed and placed in the explo- 

 sion-vessel. The explosion- vessel was then immersed in the water of 

 the calorimeter and the charge fired in the usual way, the attached 

 thermometer being read before the explosion and afterwards, continu- 

 ously, until the maximum temperature (which was reached in from two 

 to three minutes) was attained. 



To make the new calorimetric determinations as complete as possi- 

 ble, and with the view of exhibiting the differences in the heat evolved 

 due to differences in the composition of the powder, determinations 

 have been made of the heat given off by the three principal powders 

 described in the first memoir, and of three other powders differing 

 widely in their composition, and which have been made the subject of 

 analyses and experiments in these researches, viz. : — Ordinary English 

 mining, Curtis and Harvey's sporting powder, No. 6, and Spanish 

 spherical powder. 



With the small explosion-vessel the mean results obtained (Experi- 

 ments 146 to 166) were as follows, the numbers given below indicating 

 the gramme-units evolved by the combustion of 1 grm. of each de- 

 scription of powder employed. 



* One of these weighed 1,381 grms., haying a capacity of 32'5 grins. ; the other 

 weighed 3,130 grms., and had a capacity of 11883 grms. 



