176 MR J. Y. BUCHANAN ON THE 



Thus the value of d^ for a 4 gram- molecule solution of potassium bromide, 

 which is 39'358, diminishes to 36"753 for the 1 gram-molecule solution, while that 

 for rubidium chloride diminishes from 39'608 to 36*486 for the same range of con- 

 centration, and for the potassium salt of the mixed halides the two values are 41 '224 

 and 38-887. 



If we express these pairs of values as ratios, the following values are obtained : — 



RbCl. K^l+i. KBr. 



2 



Actual values = 39-358: 36-753 41-224 : 38-887 39-608:36-486 



Ratio = 1:0-9212 1:0-9433 1:0-9338 



While, therefore, the values of (iA closely approximate in the case of rubidium 

 chloride and potassium bromide, yet the ratios given above show that the rate of 

 decrease in the value of d^ for potassium bromide lies between those for the other 

 salts, but closer to that for the potassium salt of the mixed halides. 



An inspection of the values of vjm shows that all the values for RbCl are lower 

 than the corresponding values for the other two salts, although the values for potassium 

 bromide approach very close to them, while those for the potassium salt of the mixed 

 halides are much higher. 



The values of vjm for the 5 and 1 gram-molecule concentrations for each of the 

 salts are 37-468 and 34-341 for rubidium chloride, 37-557 and 35-043 for potassium 

 bromide, and 39-620 and 37-186 for the potassium salt of the mixed halides; and 

 expressed as ratios, as in the case of the values for c?A, we have for 



RbCl. 



2 



KBr. 



Actual values = 37-468 : 34-341 



37-557:35-043 



39-620:37-186 



Ratio = 1 : 0-9165 



1 : 0-9386 



1 : 0-9331 



Here, the similarity of the ratios for the potassium salt of the mixed halides and 

 potassium bromide shows a similar rate of decrease of this value vjm for these two salts, 

 while that for rubidium chloride shows a considerable departure from either of them. 



The agreements which exist, when the values ^ — and — for the three salts are 



dm m 



compared, seem to indicate that the molecules of rubidium chloride and potassium 



bromide exert almost equal effects in the displacement of solution, but the nature of 



change of displacement with change of concentration shows that the potassium salts 



are more allied in this respect. 



§ 96. The Displacement of Solutions of the Potassium Salt of the Mixed Halides 

 when considered in reference to the Displacement of Solutions of the Constituent 

 Salts. — The following table gives full data relating to the displacement, difference of 

 displacement, and mean increment of displacement of solutions of different concentra- 

 tions of potassium chloride, potassium salts of the mixed halides, and potassium iodide. 



The experiments were made with the open hydrometers A and B (see § 82) at 

 the constant temperature 19-50° C. 



