142 
Proceedings of the Royal Society of Edinburgh. [Sess. 
of the acid in water, from which, by saturation with salt, the solution 
investigated may be supposed to be derived. 
I. 
II. 
III. 
IV. 
V. 
Per cent. HCI 
Per cent. NaCl 
HCI X 100 
X\. 
IV 18 °. 
in mixture. 
in mixture. 
HCI + H 2 O. 
240 
•6650 
15-26 
5-98 
16-23 
220 
•6941 
17-14 
4-39 
17-93 
•7161 
19-36 
2-90 
19-94 
•7226 
20-58 
2-23 
21-05 
55 
•7246 
21-50 
1-85 
21-90 
55 
•7235 
22-50 
1-45 
22 84 
55 
•7196 
23-83 
MO 
24-00 
5 ? 
•6979 
26-61 
0-60 
26-77 
The figures in Columns IV and V are given in graphical form by the 
broken curve in fig. 2. Determinations of the solubility of sodium chloride 
in aqueous hydrochloric acid of the same range of concentration have been 
made by Engel at 0° and by Irvine Masson f at 30°. 
The lower unbroken curve of fig. 2 is plotted from the results of 
conductivity measurements given in Column II, and the calculated con- 
centrations of hydrogen chloride given in Column V. The relation between 
conductivity and concentration in the case of aqueous hydrochloric acid 
is shown by the uppermost curve. For this the data are given by 
Kohlrausch.+ Only five of Kohlrausch’s figures are useful here, and two 
of them represent interpolated values, but they are ample for a general 
comparison. This comparison can readily be made by noting that any 
vertical line in fig. 2 will cut the curves in three points wliich represent 
respectively, beginning with the uppermost, (I) the conductivity of a 
solution of hydrogen chloride ; (2) the conductivity of the same solution 
after saturation with salt ; (3) the percentage of salt in the same solution 
after saturation. 
It is evident that the infiuence of the salt is to lower the conductivity 
over the range investigated. With higher concentrations of acid, owing 
to the falling off of the solubility of the salt, its diminishing effect on the 
conductivity becomes less and less marked. With low concentrations of 
acid, however, this need not be the case. Since a solution containing no 
acid but saturated with salt has a considerable conductivity, it follows 
that the upper curve, in descending to the origin, must cut the lower curve. 
* Bull. Soc. Chiw., (2) 45, 654. 
f Trans. Chem. Soc., 99, 1911, 1132. 
J Leitvermogen der Electrolyte, 1898, p. 154. 
