POTASSIUM PERCHLORATE. 521 



lowest equal, with potassium chlorate than with the nitrate, 

 because the potassium of the former salt remains in the form 

 of chloride, the whole of the oxygen acting on the sulphur and 

 carbon to produce gases ; whereas the potassium of the nitrate 

 retains a part of the oxygen, at the same time as it brings a 

 portion of the sulphur and carbon to the state of saline and 

 fixed compounds, the formation of the salts more than com- 

 pensating for the volume of nitrogen set free. 



3rd. In the case where only the carbon or a hydrocarbon 

 burns, the compensation in the gaseous volumes is exactly 

 effected because each volume of nitrogen liberated from the 

 nitrate replaces an equal volume of carbonic acid combined 

 with the potassium yielded by the said nitrate. Nevertheless 

 the pressure will be increased, even in this case, with the 

 chlorate, because its temperature is higher. 



4th. The compounds formed with the chlorate being in 

 general simpler than with the nitrate, dissociation will be less 

 marked, and consequently the action of the pressures will be at 

 once more extended, because the initial pressure is greater, and 

 more abrupt, because the state of combination of the elements 

 varies between narrower limits. Hence arise shattering effects 

 rather than those of dislocation or projection. 



6. Potassium chlorate possesses another property which has 

 sometimes been utilised. Its mixture with organic substances, 

 or with sulphur or other combustible bodies, takes fire under 

 the influence of a few drops of concentrated sulphuric acid ; 

 which is due to the formation of chloric acid, which is immedi- 

 ately decomposed into hypochloric acid, an extremely explosive 

 compound and a very powerful combustive. 



This property has been utilised to cause the ignition by 

 shock of torpedoes and hollow projectiles charged with 

 potassium chlorate powder. It is sufficient to place in them 

 a tube or glass balls, filled with concentrated sulphuric acid. 



This artifice may even be employed to ignite chlorate fuses 

 for exploding dynamite or gun-cotton. 



But all these arrangements are very dangerous for those who 

 put them into execution, and they have not been practically 

 adopted. 



7. We have yet to say a few words about potassium perchlorate, 

 which is generally regarded as equivalent to the chlorate, but 

 by a mere theoretical generalisation, for it is a salt which is 

 expensive, difficult to prepare pure, and it has hardly formed 

 the object of real experiments as an explosive agent. 



Weight for weight it yields a little more oxygen than the 

 chlorate; about a sixth, viz. 46 '2 per cent, instead of 391. 



C10 4 K = KC1 + 4 . 

 But this liberation of oxygen absorbs heat; - 7 '5 Cal. per 



