87 



soluble salts of magnesium, the former is decidedly more beneficial 

 than the latter. 



As in the case of magnesium chloride, the presence of calcium 

 carbonate does not affect the neutralizing value of calcium sulphate, 

 althougli decidedl}' diminishing it in the case of magnesium sulphate 

 and sodium sulphate. It has been shown by Cameron and Seidell^ 

 that an excess of solid calcium carbonate has but a very slight effect 

 on the solubility of calcium sulphate in sodium chloride solutions at 

 the concentrations here involved. And from the general resemblance 

 between the phenomena presented by calcium sulphate in contact 

 Avith sodium chloride and magnesium chloride solutions, it is proba- 

 ble that calcium carbonate would have a like effect in the latter cases. 

 It is to be regretted that laboratory investigations of the solubility of 

 solid calcium carbonate and calcium sulphate in contact with solu- 

 tions of soluble sulphates have not yet been made. 



CALCIUM CHLORIDE IN MIXTURES. 



In the experiments with calcium chloride in mixtures with other 

 salts the following: results were obtained : 



Table IX. 



■Limits for calcium chloride in mixtures. 





Greatest endurable 

 concentration of 

 calcium chloride. 



Concentration of the 

 salts added. 



Name of salt added. 



In frac- 

 tions of a 



normal 

 solution. 



In parts 

 per 100,000 

 of solution. 



In fractions 



of a normal 



solution. 



In parts 

 per 100,000 

 of solution. 





0.25 

 a 0.3 



1,377 

 1,377 

 1,377 

 1,653 







Map-iipsinm narhnnatPi 



Saturated. 

 Saturated. 

 Saturated. 



Saturated. 





Saturated. 



Calcium sulphate 



Saturated. 



a About. 



Calcium chloride is quite generally distributed in alkali soils, being 

 usually present in small patches wherever sodium chloride is abun- 

 dant. As would be expected from the relatively very high concentra- 

 tion of the pure solution of this salt endured by roots of the white 

 lupine, the limit can not be materiall}" raised by the addition of other 

 salts. 



SODIUM BICARBONATE IN MIXTURES. 



Sodium bicarbonate was tested in mixture onl}^ with calcium sul- 

 phate and calcium carbonate together, which raised its limit of endur- 

 ance two and one-half times (see Table X). It usually occurs in 

 nature in contact with the normal sodium carbonate. 



CALCIUM SULPHATE AND CALCIUM CARBONATE IN MIXTURES. 



In the tables of limits of endurance in mixtures, as in those of pure 

 solutions, the figures do not perfectly state the case. For example, 



1 Bui. 18, Division of Soils, U. S. Department of Agriculture (1901). 



