508 AGRICULTURAL ANALYSIS 



its have been deposited according to the conditions of concentra- 

 tion and temperature to which the original solutions have been 

 subjected. The laws which govern the cooling, concentration and 

 deposition of chemical compounds in different degrees of solu- 

 bility are now well known. The theories of solution have been 

 fully expounded and verified by actual demonstration. 



It is evident that the depositions of potash salts must have come 

 from the gradual concentration or cooling, or both, of the original 

 solution. It is further evident that these original solutions were 

 secured by the action of fresh or salt water upon rock deposits 

 rich in potash. In going into solution the potash salts, in re- 

 sponse to the law of equilibrium, have combined with different 

 acids, producing salts of different degrees of solubility. The 

 salts of the same solubility, obeying a well-known law, tend to 

 be precipitated in certain given conditions of concentration and 

 temperature. Thus, nature separates sometimes completely and 

 sometimes incompletely, not only the similar salts of potash, but 

 also other saline compounds whose deposition depends upon sim- 

 ilar conditions. By the combined action of these forces the vast 

 potash deposits which are found in different parts of the world 

 but especially near Stassfurt, in Germany, have been produced. 



It is well known that almost all chemical substances which exist 

 in rocks, as incidental or principal constituents thereof are found 

 in the water which comes in contact with these rocks, whether 

 fresh or salt. It is, in fact, the accumulation of these dissolved 

 portions which gradually transforms fresh into salt water. There 

 are found in this solution, therefore, all the common metallic 

 oxids in combination with all the common mineral acids. 



The principal mineral bases are those of calcium, magnesium, 

 potassium, sodium, iron, etc., and the principal acid bases are 

 chlorin, sulfur, boron, carbon, bromin, iodin, etc. The deposits of 

 these salts may be regarded as having arisen in two series ; namely, 

 the original deposit resting upon a foundation of rock salt and 

 which consisted primarily of compounds of calcium or calcium 

 in conjunction with magnesium and potash. The pure deposits 

 of calcium sulfate are known as anhydiit and the compounds of 

 calcium magnesium and potassium sulfate as polyhalit correspond- 



