HEAT LIBERATED. 509 



Noble and Abel and the other authorities, is certainly less. But 

 nothing can be definitely settled with regard to this point till a 

 special study has been made of the heat of combustion of the 

 charcoal used in the manufacture of each of the classes of 

 powder which have been the object of the thermal measurements 

 and the chemical analysis ; as also the real proportion of the iron 

 sulphide, and even of the double iron and potassium sulphide 

 formed during combustion in the interior of an iron vessel. 



6. Heat liberated. These reservations having been made, we 

 shall give the figures found by the authorities who have measured 

 the heat liberated by the combustion of powder in closed 

 vessels. Bunsen and Schiskhoff found for 1 kgm., 619*5 Gal. ; 

 but this number, far lower than those of the other operators, 

 appears to be invalidated by some error. 



Koux and Sarrau found for 1 kgm. at constant volume in a 

 bomb filled with air, of which the oxygen contributed to increase 

 the heat liberated 



Cannon powder 753 Cal. 



Fine sporting powder 807 



B rifle powder 731 



Powder of commerce .' ... 694 



Blasting powder 570 



Tromeneuc found from 729 to 890 Cal., viz. 



Ordnance powder 840 Cal. 



English powder 891 



Blasting powder 729 



Noble and Abel gave at first (dry powder) 



KLG 696 to 706 Cal. 



FG 701 to 706 



mean, 705 Cal. They since discovered that these figures were 

 slightly too low, and they supplied after correction the following 

 new mean values : 



QUANTITIES OF HEAT LIBERATED BY THE COMBUSTION OP 

 IJ&RM. OF POWDER SUPPOSED PERFECTLY DRY. 



Pebble powder 721-4 Cal. 



R.L.G., W.A. powder 725-7 



F.G., W.A. powder 



No. 6 Curtis and Harvey's powder 



Blasting powder 



Spanish spherical 



738-3 



764-4 (733 to 784) Cal. 



516-8 Cal. 



767-3 , 



In order to be able to compare these figures with the numbers 

 calculated, we must first take into account the ash, oxygen, and 

 hydrogen contained in the charcoal, and, finally, the nitre which 

 has escaped combustion. The weight of these various substances 

 is properly known only for Noble and Abel's experiments. It 

 amounts to about four per cent, of the weight of dry powder 

 (more than one per cent, of moisture in ordinary powder). 



