514 POWDERS WITH A NITRATE BASE. 



the preponderating proportion of potassium sulphate and car- 

 bonate which is produced in every case. The production of 

 potassium sulphide and carbonic oxide is due to the secondary 

 reaction of the sulphur and charcoal on the above salts ; it plays 

 an essential part in the study of powder, as it contributes to 

 increase the volume of the gases. 



6. This being established, it may in general be admitted that 

 the heat liberated by any powder is nearly proportional to the 

 weight of saltpetre which it contains. The heat liberated by 

 blasting powder will therefore be to that of service powder in 

 the ratio of 62 to 75 ; Eoux and Sarrau actually obtained 570 Cal. 

 instead of 751 Cal. 



7. Sarrau and Vieille since found the volume of the gases 

 equal to 304 c.c. for French blasting powder at the density of 

 charge 0*6. 



This volume is greater by a tenth than that developed by 

 service powder. 



The pressures observed by them were 



Density of charge. Pressure. 



0-3 800 kgm. 



0-6 2730 



4540 



from which would result the pressure - ; a formula in which 



n 



the volume of the solid substances is not taken into account. 



8. These gases contained in 100 volumes 



C0 2 ... ... 49-4 



CO ;.. 20-5 



H 2-0 to 1-4 



CH 4 0-3 to l-4i 



H 2 S 7-0 to 5-5 



N 2 21-3 



The proportion of sulphuretted hydrogen is far larger than that 

 for ordinary powder (4 per cent.). 



The carbonic oxide forms a fifth of the volume of the gases, 

 or 20 c.c., whilst with ordinary powder it amounts only on an 

 average to one-eighth, viz. 12*5 c.c. Hence it will be seen that 

 the volume of deleterious gases is nearly double, in the case of 

 blasting powder, the volume of the s.ame gases yielded by 

 ordinary powder. 



Noble and Abel found also 7*0 of sulphurettted hydrogen; 

 but nearly equal volumes of carbonic oxide (33 '7) and carbonic 

 acid (321), which is still more disadvantageous. They obtained 

 less heat and more gas with blasting than with service powder ; 

 which affords a compensation from the point of view of 

 strength. 



1 The proportion of methane increases with the pressure (see p. 288 and 

 464). 



