DEPRESSIONS FOR ELECTROLYTES—MACGREGOR. 227 
coincides with the lower part, but in the upper part diverges to 
the left. In form the curve is thus probably trustworthy. But 
being plotted with Barnes’ coefficients it may be too high or too 
low. The R—W and J—W curves (see inset) are not open to 
this suspicion, but at the dilutions to which even their lower and 
more trustworthy parts apply, they may have begun to diverge 
unduly rightwards. If the L B—B curve (see inset) be raised 
about 2.5 per cent., as is shown to be necessary by a comparison 
of Whetham’s and Barnes’ coefficients, it comes into a position 
to the left of the R—W and J—W curves, the usual relative 
position of the curves of these observers. Loomis’s own curve 
for somewhat greater dilutions than those of the L B—B curve, 
when plotted with Whetham’s coetticients, coincides very nearly 
with the boundary line of the inset ; Wildermann’s is a little to 
the left of Loomis’s, and somewhat steeper. Both exhibit a 
slight rightward bending, as do all] the others. 
It would be difficult to draw a meaa curve with any confi- 
dence; but any such curve would run about midway between the 
1—2 and 2—4 (1.85) lines, would have a slight rightward bending 
at its upper end, and if produced with diminishing curvature, 
would run out to a point a little to the right of the 1—2 (1.85) 
intersection. 
If this intersection were the starting point of the curve, and 
if there were no association, the curve should lie wholly to the 
right of the 1—2 (1.85) line. If, as dilution diminished, 
sufficient doubling of molecules with unchanged mode of ioniza- 
tion should occur, the curve, after first bending away from that 
line to the right, would change its curvature, bend towards the 
line and cross it, and then run towards, and finally away from, the 
2—4 line, as the inean curve appears to do. 
As the 2—2 line is far to the left, the mean curve might be 
accounted for also, on the assumption of a very slight formation 
of double molecules dissociating into two ions; and a slight 
formation of such molecules would probably involve no greater 
variation of the migration numbers with concentration than 
has been observed. 
