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) a M. 
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, 43 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 ( iM ) , 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 44 used for this interpolation 
was the following: 
Mo = Mi + [(UO. - 
In this equation the two given values of M are M 1 and M v 
the two given values of iM are ( iM) x and (iM) 2 , and the values 
to be interpolated are M 0 and (iM) 0 , the value for (iM) 0 being 
derived from the formula: 
(iM) o = -~ T 
as described above. 
43 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. 
44 See Ashton, C. H., Analytic Geometry. New York (1908) 35. 
