472 Dr. A. Findlay. On a Method of Calculating Sohibilities, 



Table I. Calculation of the Vapour Pressures of Carbon Disulphide 



from the Vapour Pressures of Water. 



c = 0-0006568. 



ties ; c is a constant which may, possibly, have the value 0, but which, 

 in all the cases I have examined, has a small positive or negative value ; 

 t' and t are the temperatures at which one of the substances has the 

 two values of the solubility in question. The above equation also holds 

 no matter wlietlier the substances are ionised or are non-ionised, or whether 

 their heat of solution is positive or negative. 



A method, which is in all points analogous to that employed by 

 Ramsay and Young*' for the calculation of vapour presstires, can thus 

 be made use of for the calculation of solubilities. In order to calcu- 

 late the solubility of any substance B by means of the known values 

 of the solubility of another substance A, one proceeds as follows : 

 The solubility of B at any two absolute temperatures T'j and T'. 2 

 is determined. On dividing these temperatures into the tempera- 

 tures Tj and To, at which A has the same solubility, the ratios 

 Ti/T'i and T 2 /T' 2 are obtained. These ratios are now plotted as 

 abscissae against the corresponding temperatures of the substance A as 

 ordinates, and a straight line drawn through the two points thus 

 obtained. From this straight line curve, now, different ratios can be 

 read off, and also the corresponding values of the absolute tempera- 

 tures of substance A. By dividing the absolute temperature T of 

 substance A by the corresponding value of the temperature ratio, the 



* Loc. cit. 



