PROFESSOR 0. MASSON ON IONIC VELOCITIES. 
345 
Experimental Results. 
In Table I., the first column gives the salt used, the formula specifying the quantity 
required, in grammes per litre, for a normal solution, i.e., for one in which n = 1. 
The values of n given in the second coliunn refer to the number of gramme formula 
weights per litre. In the third column are given the ratios, u/v, these being the 
values calculated from the observed meeting points of the blue and yellow Ijoundaries. 
In one case, however, viz., that of half normal KCl, this final reading was rejected 
and the ratio calculated from the readings immediately preceding it ; for the experi¬ 
ment, otherwise one of the best as regards constancy of ujv, was spoilt just at the 
end by a disturbance that had a very visible effect on the meeting point, spoiling the 
boundaries and shifting the film formation I niillim. This was the only case of the 
kind. In the fourth column the results are expressed as ^ the transport numbers 
of the anions ; so that they may be compared with the corresponding values obtained 
for aqueous solutions by the indirect Hittorfian method. These latter are given, 
under p, in the fifth column, where the experimenter’s name (Hittorf or Kuschel) 
is signified by its initial letter. To l^e strictly comparable, these values should be for 
the same concenti'ations ; but, as such data are not in most cases available, the 
extreme values of p are given, the most dilute value being placed first. For most 
of the salts these extreme values oip refer to concentrations outside those employed 
in the jelly-tid3e experiments, so that they may be taken as including the values for 
corresponding concentrations. Two points may be noticed. The first is that, while 
the author’s results for lithium and magnesium salts fall within the p limits, those 
found hy him for sodium, potassium, and ammonium salts give smaller anion 
transport numbers than the smallest value obtained by Hittorf. The second point 
is that the new values for the chlorides tend to decrease slightly as the concentration 
increases, whereas the opposite tendency is manifested liy the Hittorfian values. 
There is, however, a general similarity that is evident on comparing the two columns. 
The last column of the table ^ives the values of -—vr—foi' fhe calculation of 
® A'H-(U-f-V) 
which all the (piantities were expressed in C.G.S. units. As already explained, the 
approximation of this value to unity may be taken as a test of the method, and it 
is evident that the result is, on the whole, satisfactory. Only the stronger sulphate 
solutions give too small values ; and it is notalile that magnesium sulphate, which 
contains two divalent ions, is abnormal even in tlie most dilute solution employed, 
though it would evidently behave normally with greater dilution. It has already 
been pointed out tliat it is salts of. divalent and polyvalent ions tliat have always 
proved least consistent with theory. 
For the calculation of the numbers in this last column it was necessary to obtain 
strictly comparable current and velocity values. Now those directly obtained in an 
VOL. CXCII.-A. 2 Y 
