DEPRESSIONS FOR ELECTROLYTES—MACGREGOR. 2925 
So do Ponsot’s, and probably Wildermann’s (not plotted), and I 
gather from Ponsot’s diagrams of Pickering’s observations, to 
which I have not access, that Pickering’s also have the leftward 
tendency. Archibald’s and Barnes’ curves show less tendency to 
diverge than those of any other observers. And although this 
may be partially, it is not wholly, due to their having worked at 
moderate dilutions only. For in several cases, pointed out below, 
the curves of other observers start on a divergent course within 
their limit of dilution. But the fact that their curves usually 
agree with Loomiss, would lead one to suspect them of a left- 
ward tendency. 
The divergence, as shown on the diagram, is most marked in 
the case of highly dissociated electrolytes (NaCl, HCl, ete.) in 
which, at great dilution, the rate of increase of ionization with 
dilution is small, the curves being crushed up, therefore, into a 
small space. But it is obvious also, in the K,SO, curves (espec- 
ially Abege’s) and the BaCl, curves (including Ponsot’s, not 
shown). And although for MgSO, and H,PO,, whose ionization 
increases rapidly with dilution, the single curves do not reveal it, 
the relative positions of the two curves in each case are what 
they might be expected to be, if they were tending unduly, 
Jones’s to the right, and Loomis’s to the left. 
This tendency is explicable at once, when we reflect that as 
it is equivalent depression that is plotted, the errors of the obser- 
vations are brought into greater and greater prominence as 
dilution increases. According, therefore, as the characteristic 
error of an observer's method of measuring total depression is 
positive or negative, will his curves of equivalent depression 
diverge at great dilution to the right or left of their true 
course. And they must diverge even if the error is very 
small, 
The equivalent depression curves of single observers are 
therefore open to grave suspicion at high dilutions ; and since one 
can never be sure that the errors of different methods will even 
approximately neutralise one another, mean curves are, at high 
Proc. & TRANS. N. S. INST. ScI., VoL. X. TRANS.—O. 
