\ 



338 ' Oil t lie Formation of Sail pet re. 



the sv>ow which is combinefl with the salifiable bases of the 

 .tile : in summer the former is brought bv tlie rains. 



li.' it be easy, from the above theory, to explain how the 

 nitric acid comes to be found in the earth of India and 

 Spain, as well as in the tiles of the roof, it gives us no as- 

 sistance in explaining why nitrate of potash is found there 

 in preference to nitrates of lime and of alumine, since tiles 

 are made of these salifiable bases ; and without doubt they 

 help to fonn the soils of Spain and Tndia, while no potash 

 at all enters into their composition. My object was to 

 point out the origin of the nitric acid in raost salt()etre 

 substances, and not that of potash : I shall merely add, for 

 the sake of those who ask reasons for every thing because 

 they wish to account for every thing, that it is a fact of 

 observation, uaiuely, that tlic same njaterials which are 

 applied to the formation of nitrates, when exposed to a 

 damp and ^tagnant air, yield nothins; for the most part but 

 nitrate of lime ; whereas, when they «re exposed to a dry 

 and agitated air, they yield almost nothing but nitrate of 

 potash*. 



It is not enough to establish a tlieory, we must also rea- 

 der it as useful as possible; and for this reasou I have pub- 

 lished this paper. 



The most direct application that can be made of these 

 hints is without doubt the manufacture of saltpetre. In 

 fact, there arc about three millions of pounds of saltpetre 

 rnade annually ; and for this it requires at least 796 mil- 

 lions of saltpetre materials, since f estimate about six 

 ounces an being the produce of each cut. of materials. At 

 least an equal quantity of water is used in lixiviating these 

 materials ; and if we admit thai there is only 0*0001 of ni- 

 tric acid in this water, it follows that it would give as the 

 result 79,800 pounds of acid; which, adopting the propor- 

 tions given by Bcrthollel for the component parts of nitrate 

 of potash, would give 164,130 pounds of this salt. 



Rain and snow water may therefore be advantageously 

 employed, not only in lixiviating saltpetre substances, but 

 for watering artificial nitre-works, and by this means the 

 produce will be greatly increased. 



• Recueil de Mcmuires sur U Sal^t'trc. 



XLVIl. Neip 



