OF AQUEOUS SOLUTIONS.—BARNES. oe 
In this table it will be noticed in the first series of observa- 
tions, where the concentration of the constituent solution of 
sulphuric acid is constant, while the constituent solution of hydro- 
chloric acid has a variable concentration, that the calculated 
values are all greater than the observed, and that the differences 
gradually increase as the concentration of the hydrochloric acid 
increases. This is also true for the second and third series, 
except in the case of the weaker hydrochloric acid solutions 
where the calculated is now less than the observed value. Prof. 
MacGregor has shown in a note to my former ‘paper, in which 
I drew attention to a regular progression similar to the above 
for series of solutions of potassium chloride and potassium sul- 
phate, which were for the most part of moderate concentration, 
that the regular progression observed may be due to two sources 
of error. The second source, namely, the impossibility of draw- 
ing with perfect accuracy the dilution-ionic-concentration 
curves, has, I think, been considerably reduced, for in place of 
drawing these curves, which for moderate concentration curve 
quite rapidly, concentration-specific-conductivity curves were 
employed, these curves having but slight curvature and being 
thus easily interpolated. The other source of error, namely, 
the using for the value of the ionization coefficient the quotient 
of the specific molecular conductivity by the specific molecular 
conductivity at infinite dilution, still remains. In the above 
fourth series where the first two mixtures are of moderate con- 
centration and the other four may be called dilute solutions, this 
regular progression has disappeared and the differences are all 
negative, except in the first mixture. The disappearance of 
the progression is consistent with its being due to the above 
sources of error; for in dilute solutions they both produce a 
very small effect upon the result. Two reasons may be assigned 
for the signs being all negative in the fourth series:—(1) The 
use of the above values of the specific molecular conductivity at 
infinite dilution ; for if either of the values used should not be 
correct then it would clearly produce an error of the same sign 
1 Loc. cit. 
