32 



MAGNESIUM CHLORIDE IN MIXTURES. 



The results of experiments with magnesium chloride in mixtures 

 with other salts are shown in the following table : 



Table V. — Limits for magnesium chloride in mixtures. 



Name of salt added. 



None 



Sodium carbonate -.- 



Sodium sulphate 



Sodium chloride. 



Calcium chloride 



Magiiesium carbonate 



Calcium carbonate 



Calcium sulphate ■ 



Calcium sulphate and calcium carbonate 



Greatest endurable 

 concentration of 

 magnesium chloride. 



In frac- 

 tions of a 

 normal 

 solution. 



0.0025 

 .0025 

 .01 

 .01 

 .1 



.0025 

 .04 

 .2 



In parts 

 per 100,000 

 of solu- 

 tion. 



12 

 12 

 48 

 48 

 480 

 12 

 192 

 960 

 960 



Concentration of the 

 salts added. 



In fractions 



of a normal 



solution. 



0.00375 



.01 



.02 



.15 

 Saturated. 

 Saturated. 

 Saturated. 

 Saturated. 



In parts per 

 100,000 of 

 solution. 



19.5 



80 



116 



726 



Saturated. 



Saturated. 



Saturated. 



Saturated. 



In the alkali soils of the Western United States magnesium chloride 

 rarely occurs in such large quantities as to be regarded as more than 

 secondary in importance.^ 



As in tlie case of magnesium sulphate, calcium is found to be much 

 more effective than sodium in neutralizing magnesium, but here cal- 

 cium chloride is relatively more effective than with magnesium sul- 

 phate, raising the limit for magnesium chloride one-half (instead of 

 only one-third) as far as does calcium sulphate. But calcium is much 

 less effective with the chloride than with the sulphate of magnesium, 

 as is evident from the relative efficac}^ of calcium sulphate in raising 

 the limits of endurance of the two magnesium salts. Hence we have 

 here another indication (as in the case of calcium chloride added to 

 magnesium sulphate) that chlorine ions by their presence lower the 

 neutralizing efficacy of calcium; although in the absence of the latter 

 base, magnesium chloride is only one-half as toxic as is magnesium 

 sulphate. While the beneficial effect of calcium sulphate upon mag- 

 nesium sulphate is decreased by the addition of an excess of calcium 

 carbonate, the presence of the carbonate does not affect the value of 

 calcium sulphate as an antidote to magnesium chloride. 



While calcium carbonate is equally effective in raising the limits 

 of the two soluble magnesium salts (sixteen times), magnesium car- 

 bonate, which raised the limit of magnesium sulphate eight times, 



1 Magnesium rarely makes its specific effects upon plant life felt in the " alkali " 

 soils, owing to the omnipresence there of considerable calcium salts. In certain 

 areas of the Eastern States, notably in the so-called " serpentine barrens " of Penn- 

 sylvania and Maryland, it appears to be relatively more important, probably 

 because it is .there present in excess oyer calcium, although the actual amount of 

 both, which may be present in the soil solutions at any given time, must be 

 extremely small. 



