866 



DR S. M. JOHNSTON ON THE BOILING AND FREEZING POINTS OF 



Jones and West have given some conductivity values for acids for which I have 

 also obtained data ; consequently, it is possible to compare their results with mine. 

 It may be noted that the differences between the values obtained, which are not large, 

 are covered by the errors which have resulted from the volumetric analysis of the acids 

 supplied made to obtain their concentration, the errors attaching to making up and 

 diluting solutions perhaps several times, the error of temperature or of the experimental 

 observation of conductivity, and difference in the purity of the water # used. 



Nitric Acid. 

 Mine. 



Nitric Acid. 

 Jones and West. 





Potassium 



Nitrate. 





Litres per 

 Grm. eq. 



Conductivity. 



Litres per 

 Grm. eq. 



Conductivity. 



Litres per 

 Grm. eq. 



Conductivity. 



KOHLRAUSCH. 



Conductivity. 

 Krannhals. 



Conductivity. 



Jones and 



West. 



095 



40 







2 



8 



83-9 



83-3 

 96-6 



83-1 

 95-6 



•190 



98-7 







10 



103-7 







•380 



146-4 





... • 



16 

 20 



106-7 



101-4 



1003 



1 



1942 



4 



222-4 



32 

 100 

 128 



114 



105-7 

 1127 



104-3 

 1093 



10 



227-1 



8 



16 



32 



128 



226-9 

 231-3 

 235-4 

 238-3 



... 









1000 



235-0 



1024 



231-4 











The following tables contain the results of computations showing the amount and 

 character of the hydration which, according to the hydration theory, must be assumed in 

 order to account for the variation with concentration of the so-called boiling point constant. 



These computations assume (l) that the ionization coefficients can be determined 

 with sufficient accuracy from observations of electrical conductivity ; and (2) that the 

 elevation produced in the boiling point (or depression of the freezing point, as the case 

 may be) by each gramme molecule or gramme ion (hydrated or unhydrated) in a 

 given quantity of water to which salt has been added is independent of the concentra- 

 tion of the solution thus formed. 



1 am quite aware of the doubtfulness of these assumptions, but it may be pointed 

 out with regard to the first that in the computation formulas which are given below the 

 factors involving the ionization coefficients a are 1 + a, 1 + 2a, etc., and that, con- 

 sequently, the percentage error of the result, due to errors in the coefficients, is much 

 less than the percentage errors themselves ; and, with regard to the second, it should be 

 noted tli at through considerable concentration ranges the diminution of vapour pressure 

 has been found to be at any rate roughly proportional to concentration. 



* Trans. Roy. Soc. Edin., 45, 211, 1906. 



