36 



As in the case of all the other salts except sodium carbonate, cal 

 cium chloride is less effective than calcium sulphate, raising the limit 

 only twentj-seven times. In this case, as in the mixture of calcium 

 chloride with magnesium sulphate, a crj^stalline precipitate of calcium 

 sulphate is formed, so that it actualh^ becomes a case of the contact 

 of calcium sulphate with a solution of sodium chloride, and the same 

 limit was obtained b}^ a direct test of this latter mixture. Calcium 

 carbonate is much less effective in neutralizing sodium sulphate than 

 in counteracting the toxic action of magnesium salts. 



Calcium sulphate is more effective as an antidote to sodium sulphate 

 than to any other salt tried except magnesium sulphate. In both 

 these cases the anion of the added salt is the same as that of the more 

 toxic one; hence the cathions alone seem to oiDcrate. Possibly a dou- 

 ble salt of sodium and calcium is formed in this mixture. Since cal- 

 cium sulphate is much less efficacious in neutralizing the chlorides of 

 magnesium and sodium than the corresponding sulphates, while it is 

 generally more beneficial than is calcium chloride, it seems almost 

 certain that the beneficial action of Ca ions is in some way hindered 

 by the presence of CI ions. That CI ions are in themselves less toxic 

 than are SO4 ions would appear from the fact that the chlorides of 

 magnesium and of sodium are less injurious in j)ure solution than are 

 the corresponding sulphates. 



SODIUM CHLORIDE IN MIXTURES. 



Experiments with sodium chloride in mixtures with other salts 

 yielded the results shown in the following table : 



Table VIII. — Limits for sodium chloride in mixtures. 





^ro^n*^c1n??ft^or?fl ^— 5S\«Ted^^*"^ 

 sodium chloride. ^^^^^ ^'^'^^d- 



Name of salt added. 



+w,o ^f ' III parts In fractions In parts per 

 T?n™i per ll»f>-00(' of a normal liJO,0(J() of 

 solution of solution, solution. solution. 



None .. . 



0.02 

 .2 

 .04 

 .06 

 .2 

 .2 



116 i 





1,160 i 0.2 1,101 





232 Saturated. Saturated. 





348 Saturated. 1 Saturated. 



Calcium sulphate 



1.160 Saturated. Saturated. 



Calcium sulphate and calcium carbonate 



1.160 Saturated. Saturated. 



Sodium chloride is probably the most widely distributed and gen- 

 erally abundant of the soluble components of alkali soils, occurring 

 practically wherever the land is notablj^ impregnated with these 

 noxious salts. ^ As the above table shows, calcium sulphate and cal- 

 cium chloride are equally effective in neutralizing the toxicity of 

 sodium chloride, although in the case of sodium sulphate and the 



A notable exception is the Billings area in Montana. 



