546 The Philippine Journal of Science 1920 
the degree of dissociation of a salt is known for a given volume- 
molecular concentration, M, the particulate concentration, iM, 
may be calculated by means of the equation: 
iM =1-+ (n—1) aM. 
In this equation n is the number of ions formed when a molecule 
of the salt is dissociated, and a (given just below) is the degree 
of ionization, or the fraction of the whole number of molecules 
that dissociates at a given concentration. For potassium chlor- 
ide n has a value of 2, and the equation becomes: 
iM = (1 +a) M. 
Values for the degree of ionization a of potassium chloride 
were obtained from Noyes and Falk’s compilation,*® based upon 
determinations of the conductance ratio. The volume-molecular 
concentrations (M) and the corresponding values of a are the ital- 
icized values given in the third and fourth columns, respectively. 
The corresponding values of iM for this salt, calculated by means 
of the last-mentioned formula, are the italicized values in the 
sixth column. Each of these italicized values in the sixth column 
represents the calculated osmotic concentration (1M) , correspond- 
ing to a known volume-molecular concentration (M) of potas- 
sium chloride. 
As has been explained, each of the values in roman type in 
the sixth column represents an osmotic concentration (iM) corre- 
sponding to an unknown volume-molecular concentration (M). 
These unknown values have been calculated by interpolation 
between the italicized values in the third column, assuming a 
linear relationship. The formula +4 used for this interpolation 
was the following: 
Mo = Mi, + [GM)o — (im) 22s _. 
3 ( M);] ((M)2 — (iM), 
In this equation the two given values of M are M, and M,, 
the two given values of iM are (tM), and (iM).,, and the values 
to be interpolated are M, and (iM),, the value for (iM), being 
derived from the formula: 
(iM), =e 
as described above. 
: © Noyes, A. A., and Falk, K. G., The properties of salt solutions in rela- 
tion to the ionic theory. III. Electrical conductance, Journ. Am. Chem. 
Soc. 34 (1912) 474 and 475. 
“See Ashton, C. H., Analytic Geometry. New York (1908) 35. 
