SPECIFIC GRAVITY AND DISPLACEMENT OF SOME SALINE SOLUTIONS. 181 



Concentration of the Solutions (m). — The highest concentrations were those of 

 slightly supersaturated solutions in the case of magnesium and calcium chlorides. The 

 solution of magnesium chloride which is saturated at 19 '50° C. contains 5 "91 82 gram- 

 molecules of salt in 1000 grams of water, and is the second of the series of strong 

 solutions of this salt. The solution containing 5*5 gram-molecules of salt was prepared 

 from this solution, and then solutions were experimented on having a common difference 

 of 1 gram-molecule, and ranging from 5'0 to TO gram-molecule. 



The 6 '6 27 gram-molecule solution of calcium chloride is supersaturated, and the 

 6 "6 13 gram-molecule forms a solution which is saturated with CaClg at 19 "50° C. This 

 solution is of interest as being the mother-liquor obtained after crystallisation from the 

 solution which showed the condition of unrest described in Section XV. The experi- 

 ments on this solution were made at a much earlier date than the others included 

 in this table, but the results are included here in order to give a complete list of the 

 experiments made. 



As will be seen, the solutions for which w = 6'6 to 6-0 decrease regularly in 

 concentration by 0*1 gram-molecule. They were made in order to trace the changes of 

 displacement due to small changes of concentration in nearly saturated solutions. For 

 m = 6'0 to 1"0 gram-molecules the common difference of concentration of consecutive 

 solutions is 1 "0 gram-molecule. 



Discussion of Results. Specific G7'cwity. — With regard to the agreement of 

 the individual results among themselves for a particular series, the analysis of the 

 specific gravity results in the case of the calcium chloride solution containing 6*3 gram- 

 molecules of salt in 1000 grams of water (see § 90) affords a fair criterion, and the 

 usual number of series of observations made for each concentration was six, three with 

 each hydrometer. In all the experiments the results of which are included in these 

 tables, the temperature of the solution remained constant at 19 "50° C. Comparing the 

 specific gravities of solutions of the three salts, having the same molecular concentration, 

 and m being less than 1 "0, the values in all cases increase with increasing molecular 

 weight. Thus, for m=l/2 the specific gravities of the solutions rise from 1*025620 for 

 BeClg to 1-037385 for MgClg and to 1-043739 for CaCl2, and the same feature is 

 observed in comparing the values for all concentrations down to w = 1/1024. 



It is interesting to compare the increments of specific gravity (S— 1), (which for 

 this purpose are conveniently multiplied by 1000), of the solutions with the molecular 

 weights of the salts dissolved in them. We have them in the following table, for 

 solutions for which m = l/2 : — 



MR = BeCl.^. MgCIa. CaCls. 



1/2 MR = 40 47-66 55-5 



1000 (S-1) = 25-620 37-385 43739 



^T^f.7.^^ = 0-640 0-784 0-784 



1/2 MR 



When w = l/16 and 1/128 we have the following values : — 



