520 POWDEKS WITH CHLORATE BASE. 



plex and advanced combinations, such as potassium sulphate 

 and carbonate, or carbonic acid, which are produced by nitrate 

 powder. It is for this reason that the pressures developed in 

 the first instance will be nearer the theoretical pressures with 

 chlorate than with nitrate powder, and the variation in the 

 pressures produced during the expansion of the gases will be 

 more abrupt, being less checked by the action of the combina- 

 tions successively reproduced during the cooling. 



5. The explanations just given apply not only to powders in 

 which potassium chlorate is mixed with charcoal and sulphur, 

 compared with analogous powders with nitre as base, but also 

 comprise all powders formed by the association of the same 

 salts with other substances. It can be shown that this is so, 

 without entering into special calculations, for which the exact 

 values would in the majority of cases be wanting. 



Now, our comparisons are based on the following data, which 

 present a general character : 



1st. Both salts employed in equal weights supply to the 

 bodies which they oxidise the same quantity of oxygen. 122*6 

 grms. of chlorate yield 6 equiv. or 41 grms. of oxygen ; that is to 

 say, 8 grms. of oxygen for 20 grms. of chlorate ; whilst 101 grms. 

 of potassium nitrate yield only 5 equiv., or 40 grms. of available 

 oxygen, viz. 8 grms. of oxygen to 20*2 grms. of salt. Hence 

 it follows that both salts must be employed in equal weights 

 in the greater number of cases. 



Now, one and the same weight of oxygen, 8 grms., yielded by 

 potassium chlorate liberates + 11 Gal. more than free oxygen ; 

 if it be yielded by the nitrate, it produces on the contrary 

 + 8*3 Cal. less j 1 which makes a difference of 19'3 CaL, or 6*95 

 Cal. per gramme of salt employed. 



The formation of the same compounds will therefore liberate 

 more heat with the chlorate than with the nitrate, and the 

 excess will subsist, even in taking into account the union of 

 the acids of sulphur and carbon with the potash of the nitrate. 



This greater quantity of heat will give rise to a higher 

 temperature, since the mean specific heat of the products is less 

 with the chlorate than the nitrate. The mean specific heat of 

 the products at constant volume may be calculated theoretically 

 by multiplying the number of atoms by 2 '4, and dividing the 

 product by "the corresponding weight. Now, the weight of the 

 combustible body being the same will require the same 

 respective weights of nitrate and chlorate, according to what 

 has just been said ; but the latter will correspond to a less 

 number of atoms, since the equivalent of chlorine is greater 

 than that of nitrogen. 



2nd. The volume of the permanent gases is greater, or at the 



1 Supposing it to act upon a carbonated body, the carbon of which is 

 changed into potassium carbonate. 





