30 



WORK OF C. M. STINE. 



MIXTURE OF CALCIUM CHLORIDE AND STRONTIUM CHLORIDE. 



For the sake of comparison, the lowerings of the freezing-point which would be 

 obtained from the mixture of calcium chloride and strontium chloride are given in 

 table 17, basing them upon the same method of calculation as that already given in 

 detail for table 13. The symbols used have the same significance in the two tables. 



Table 17. Freezing-point Lowering, Calculated and Found 



and Strontium Chloride. 



-Mixture of Calcium Chloride 



m 



0.3 CaCl 2 

 0.3SrCl 2 . 

 0.5 CaCl 2 

 0.5SrCl 2 . 

 0.7 CaCl 2 

 0.7 SrCl 2 . 

 0.9 CaCl 2 

 0.9 SrCl 2 . 

 1.3 CaClo 

 1.3 SrCl 2 . 

 1.7 CaCl 2 

 1.7SrCl 2 . 

 2.1 CaCl 2 

 2.1 SrCl 2 . 



m c 



M 



Mr. 



L' c 



L' 



Sum. 



0.15 

 0.15 

 0.25 

 0.25 

 0.35 

 0.35 

 0.45 

 0.45 

 0.65 

 0.65 

 0.85 

 0.85 

 1.05 

 1.05 



6.0 



3.9 



8.2 



5.5 



9.7 



7.1 



11.7 



9.0 



15.7 



12.4 



18.9 



15.7 



21.9 



18.7 



5.6 

 3.5 

 7.3 

 4.6 

 8.3 

 5.7 

 9.5 

 6.9 



11.7 

 8.5 



12.8 

 9.7 



13.3 



10.3 



4.186 

 4.461 

 4.056 

 4.266 

 3.942 

 4.127 

 3.791 

 4.030 

 3.576 

 3.797 

 3.378 

 3.593 

 3.171 

 3.400 



4.65 

 4.76 

 4.67 



i 



I 



4. 



4. 



4. 



4. 



.65 

 .63 

 .60 

 .57 

 .60 

 .53 

 4.48 

 4.39 

 4.35 

 4.17 

 4.17 



5.001 

 5.32/ 

 5.161 

 5.43/ 

 5.261 

 5.51/ 

 5.361 

 5.70/ 

 5.561 

 5.92/ 

 5.611 

 6.00/ 

 5.49) 

 5.92/ 



It will be noted that in table 17, again, as in the case of the mixture of calcium 

 chloride and magnesium chloride, the difference between the lowering as calculated 

 upon the hypothesis that, for the more dilute solutions, at least, the hydrates formed 

 by a salt in separate solution are related to those formed by the same salt in the 

 mixture at corresponding concentrations as the amount of water present as solvent 

 in the mixture the difference between this and the lowering found experimentally 

 becomes increasingly large. This has been discussed in the preceding case. 



The method of calculating the composition of the hydrates existing in a mixture 

 of two salts with about the same hydrating power, such as calcium chloride and mag- 

 nesium chloride, was based upon the assumption that the values of M in their sepa- 

 rate solutions represent the relative hydrating powers under the same conditions 

 for the two salts in their mixtures. While this applies where the hydrates formed 

 are of approximately the same degree of complexity, it would involve an error in the 

 case of two salts of very different hydrating powers. For, if the power of forming 

 hydrates, i. e., of eliminating water from the sphere of action as solvent, differs, then, 

 when two such substances are mixed, if a decrease in the amount of water eliminated 

 from the sphere of action as solvent occurs, this decrease must be assigned to the 

 two salts inversely as their values of M in separate solutions. This follows from 

 a consideration of the fact that the salt with greater hydrating power will have, 

 consequently, greater power of dehydrating the salt with lesser hydrating power. 

 Therefore, the salt which has less power to unite with water must suffer the greater 

 loss in water of hydration in the presence of the salt with stronger hydrating power. 



Upon this assumption the following method of calculating the approximate 

 composition of the hydrates in such a mixture has been worked out : Take the case 

 of a mixture consisting of one volume of 0.3 N strontium chloride and one volume 

 of 0.3 N calcium chloride. 



