SOLUTIONS 183 



very numerous. A very important research was undertaken a 

 few years ago on the formation of oceanic salt deposits by 

 Professor Van 't Hoff, and carried on by him with the aid of his 

 students for many years, till shortly before his death in 1911. 

 This had special reference to the famous salt deposits at Stass- 

 furth in Prussia, from which supplies of potassium and magnesium 

 salts have been distributed in large quantities during many years 

 past, and the lack of which has caused some inconvenience out- 

 side Germany during the war. The salts from Stassfurth which 

 have become familiar in commerce are : 



Carnalite . . KC1, MgCl 2 , 6 H 2 0> 



Kainite . . KC1, MgS0 4 , 3 H 2 0, 



Kieserite . . MgS0 4 , H 2 0, 



Sylvite . . KC1. 



There are many other double salts in these deposits, but the 

 result of Van 't HofPs work has been to explain how it came 

 about that these compounds were formed and in what order. 

 Temperature has a good deal to do with it, but pressure is also 

 a condition which may modify the composition of some of the 

 salts in the solid state as they occur in the veins under- 

 ground. 



Another important question which has been studied within 

 recent years is that which relates to the formation of the double 

 carbonate of magnesium and calcium which constitutes the 

 mineral called dolomite, which is so abundant as to form whole 

 mountains in some parts of the world, the Eastern Alps for 

 example. The substitution of magnesium carbonate for calcium 

 carbonate in such rocks is the problem which has occupied 

 chemical geologists without the discovery of a definite answer in 

 each case. The examination and analysis of the core obtained 

 from a bore hole drilled into the atoll of Funafuti led Professor 

 Judd in 1904 to the conclusion that the original calcium carbonate, 

 secreted by the corals, has been partly replaced by magnesium 

 carbonate after the death of the organisms. While the pro- 

 portion of magnesium carbonate near the surface is from 12 to 16 

 per cent, at a depth of 637 to 1114 feet, it increases and is main- 

 tained with some variations at 40 per cent, a proportion which 

 approaches the amount required (45-65) to form dolomite. The 

 true explanation of this change is yet to be sought, but a further 



