o'l 
The nitric acid in union with potash forms another impor¬ 
tant mineral. Saltpetre , or JYitre , as it is called, is observed at 
various places in Europe and Asia, in the form of an efflor¬ 
escence, on limestone rocks and caverns,* but the article 
used in commerce is generally the result of artificial pro¬ 
cesses. It is usually made from the decomposition of ani¬ 
mal and vegetable matter, formed into beds, and exposed to 
the action of the air. The oxygen of the atmosphere, and 
the azote originating from the disorganization of the materi¬ 
als used, unite and form nitric acid, which is combined with 
•the potash of the beds.f This compound undergoes puri¬ 
fication, and is then used in manufactures. Mitre was made 
in 1810, in several of the southern states together with 
Massachusetts to the amount of near half a million of 
pounds.f in the state of Kentucky, calcareous caves are 
found in considerable number, containing this mineral in 
combination with the earth. From this, it is extracted by 
lixiviation, and afterwards boiled to the crystalizing point. 
This is the mode commonly pursued both in this and in for¬ 
eign countries. In France, however, at the eventful crisis 
of her revolution, it was found too tedious, and indeed insuf¬ 
ficient to supply the armies with this important constituent 
in the making of gun powder. Purification by repeated ab¬ 
lutions, which carries off the deliquescent salts, was then 
adopted with success, and from that period to the present 
has been universally followed in that country.§ In one cav¬ 
ern alone, in Kentucky, it is calculated by Dr. Brown, that 
* This is annually re-produced. The theory of its formation 
is stated in Murray’s Chemistry, vol. 3, p. 453. 
f Vide an account of the modes pursued in Prussia, Sweden, 
Malta, and Switzerland, for the making of nitre, in C.haptal, vol. 
4 , p. 158. 
^ Virginia, 59,175 
Kentucky, 201,937 
Massachusetts, 23,600 
East Tennessee, 17,531 
West Tennessee, 144,895 
447,138 Ibp, 
Mitchill’s View, $tc. A. R. vol. 2, p. 295. 
§ Chaptal’s Chemistry, vol. 4, p. 138. 
