SPECIFIC GRAVITY AND DISPLACEMENT OF SOME SALINE SOLUTIONS. 189 



SO obtained as CaClaG-SHaO and CaCl^e-dHgO respectively. It is obvious, therefore, that 

 the crystals which were deposited had the composition CaClaGfTaO, and that the excess 

 of water indicated by the analyses was due to some adherent mother-liquor, from which 

 it is almost impossible to free the crystals. 



That the crystals deposited in the first experiment had the composition CaCLGHaO 

 is confirmed by the thermal data already set forth. 



The weight of original calcium chloride solution which crystallised in the cylinder 

 was 806'61 grams. It contained 44'48 per cent. CaClz. 



The mean of the first series of specific gravities— 1 '4 460 19 — is taken as the specific 

 gravity of this solution when at rest. 



The concentration of the solution is therefore : — I 



Per Cent. By Weight. 



CaClj . . 44-48 359 '0 grams. 



Water . . 55-52 447 6 „ 



Total . . 100-00 806-6 „ 



After the crystallisation was ended, and with the solution at a temperature of 

 I9'5° C, one determination of the specific gravity of the mother-liquor gave the 

 result 1-423500. 



The concentration of the mother-liquor determined by analysis was 42'33 per cent., 

 equivalent to 734"0 grams, or 6'613 gram-molecules CaCla per 1000 grams water. 



The crystals (CaClgeHgO) contain 50"685 per cent. CaCla- 



The cooling observations showed that the heat evolved in the act of crystallising 

 was 4276 gr.° C. 



According to Thomsen, the heat of solution of CaClaeHgO is - 4340*0 gr.° C. ; there- 

 fore on thermal evidence alone 215'5 grams, or 0'984 CaClzBHaO, has separated out. 

 But, on the basis of the analytical estimations made on the supersaturated solution 

 and the mother-liquor, we find that 210*3 grams of crystals separated out of 80661 grams 

 of solution, or 096 gram-molecule CaClaeHaO. The agreement of these two computed 

 values is excellent. 



We accept then as the quantities of crystals and mother-liquor 210*3 grams and 

 596 '3 grams respectively. 



§ 110. The nature of the experiments having been indicated, and the general 

 character of the thermal change and the alterations in specific gravity mentioned, the 

 following table, IIa., gives a complete account of the individual observations of specific 

 gravity made, together with the corresponding displacements calculated from them. 



Table IIb, gives a similarly complete account of the individual observations of 

 specific gravity in five series made in the solution 6*3 CaClg-f- 1000 grams of water at 

 19*5° C, with the corresponding displacements calculated therefrom. The solution of 

 calcium chloride saturated at 19*5° C. is 6613 CaClg-t-lOOO grams of water; therefore 

 the 6*3 CaClg solution, though of high concentration, is sufficiently removed from 

 saturation to exhibit the tranquillity of a dilute solution. 



