516 AGRICULTURAL ANALYSIS 



sulfate with seven molecules of water of crystallization appears as 

 an additional salt. The deposit having been removed, this hy- 

 drate of magnesium sulfate and potassium chlorid is now depos- 

 ited until finally magnesium sulfate with six molecules of water 

 of crystallization is added to these two salts as a new constituent. 

 From this point onward the hexahydrate of magnesium sulfate 

 with potassium chlorid crystallizes until carnallit makes its ap- 

 pearance. After this the hexahydrate of magnesium sulfate with 

 carnallit constitutes the deposit until magnesium chlorid appears 

 and now the solution dries up completely to a mixture of the three 

 last named substances. 



Collecting once more the quantitative measurements connected 

 with these deposits, we have the following table: 



In mols. per 1000 mols. H S O 

 Saturation with K 2 C1 S MgCl 2 MgSO 4 



M. Potassium chlorid, potassium sulfate, schonit 25 21 n 



N. Potassium chlorid, MgSO 4 .7H 2 O, schb'nit 9 55 16 



P. Potassium chlorid, MgSO 4 .7H 2 O, MgSO 4 .6H,O 8 62 15 



Q. Potassium chlorid, carnallit, MgSO 4 .6H 2 O-. 4.5 70 13.5 



R. Magnesium chlorid, carnallit, MgSO 4 .6H 2 O- 2 99 12 



The next thing is to represent these numbers graphically, and 

 when this has been done we are presented with a complete view 

 of the whole process of crystallization. 



To do this a third dimension is obviously required. We add 

 a third axis passing through O, vertical to the former system of 

 axes (Fig. 45), and along this we lay off the number of molecules. 

 In practice this may be done conveniently by means of a model 

 consisting of a piece of wood in which vertical needles are set 

 at the proper places, with their lengths adjusted to the number of 

 molecules. A horizontal projection on this model is shown in 

 Fig. 46, whose border obviously coincides with the outline of Fig. 

 45, and whose points, M,N,P,Q, and R, represent the above data. 

 This having been done, each pair of points representing satura- 

 tion with the same two salts, for example, M and L, where in 

 both cases saturation with the sulfate and chlorid of potassium 

 exists, is connected by a line. 



These lines divide the figure into areas, each of which corres- 

 ponds to saturation with a definite salt, as follows : 



