246* DESCRIPTION OF A NITRE CAVE. 



on this subject, (Philosophical Magazine, V. IX. p. 355.) which 

 appear to me very interesting. By his mode of distilling wood 

 in iron cylinders, he deprives it completely, of all the volatile 

 oil, hydrogenous gas and pyroligneous acid. The charcoal 

 prepared in this way, possesses uniformly the same properties, 

 and by the employment of it, the powder now used in the 

 British ordnance, is increased in strength one third. 



The gun-powder manufactured in the United States, is said 

 to be defective, from a disposition either to effloresce or de- 

 liquesce. The salts most liable to effloresce are such as have 

 soda for their base. In many of our saltpetre caves, small 

 quantities of the sulphate of soda have been discovered, which 

 for want of sufficient care or skill in refining, are suffered to 

 remain with the nitre. The disposition to efflorescence ap- 

 pears to be directly opposite to that of deliquescence ; as in 

 the one case, the air has a stronger affinity for the water of 

 combination of the salt than that which exists in the salt for 

 the water; in the other case the salt attracts moisture from its 

 combination with air. It would seem then, that, as the air 

 is capable of depriving the sulphate of soda of its water of 

 combination, and as nitrate of lime attracts moisture from the 

 surrounding air, it is possible, that a mixtui j of these two salts 

 may be so made with nitrate of pot-ash, that the nitrate of 

 lime may deprive the sulphate of soda of its water of combi- 

 nation, and in consequence of this addition of water, deli- 

 quescence may ensue, even when the atmospheric air and 

 moisture are excluded. If Count Rum ford is correct in sup- 

 posing that the explosive force of gun-powder depends not 

 upon the evolution of permanently elastic fluids or gases; but 

 upon the almost instantaneous conversion of the water of com- 

 bination existing in the powder, into steam by the caloric re- 

 suiting from its inflammation ; this explosive force may be di- 

 minished for want of that water which might have escaped by 

 efflorescence, or on account of the slow combustion of the pow- 

 der consequent on deliquescence. 



A concern for the glory and defence of our country should 

 prompt such of our chemists as have talents and leisure to in- 

 vestigate this interesting subject. In 1776, at the request of 



