492 Messrs. Smith and Moss on the Contact 
quantities of dissolved oxygen, the p.d. between the large 
Hg electrode and the solution sometimes changed perceptibly 
during the short time required to determine the electro- 
capillary curve. It will be seen, however, that a series or! 
curves with practically equal maxima of! surface-tension was 
now obtained. The null solution lies between IV. and V., 
and corresponds within the limits of experimental error with 
a solution of which the maximum of the electrocapillary 
curve is at the origin. Part of the difference between the 
numbers in columns 4 and 5 was certainly due to increase 
with time of the p.d. Hg | solution. The capillary curves 
were taken first and are not exactly parallel to the deci- 
normal KC1 curve. The distance decreases slightly towards 
the lower ends of the curves. The p.d. between the 
strongest of the solutions and the n/10 KC1 solution was 
probably less than a millivolt (cf. Palmaer, Zeit. p. Chem. 
1. c. 1907, p. 155). 
By examination of the data for solutions IV. and V. it is 
seen that a null solution of the present kind, interpreted 
according to the assumptions of Palmaer, would give, for 
the p.d. Hg | n/10 KC1, a value agreeing with his result. 
But, as will be seen, his assumption of zero p.d. between 
Hg and the null solution is not at all necessary. The only 
necessary conclusion is that the p.d. between the still Hg 
and the solution is the same as that between the dropping 
Hg and the solution. 
From the data in the Table it is seen that, for reasons 
already given, the maxima being practically equal in all the 
solutions, the p.d. between the dropping electrode and the 
solution should be in every case the same. This result is 
probably of significance in the theory of . electrocapillarity. 
Its truth is shown by the practical equality of all the numbers 
in Column 7. 
§ 17. jEjfect of Oxygen upon Paschens relation. — With 
respect to the data in columns 3 and 6, § 16, showing the 
fulfilment of the Paschen relation for the present series of 
electrolytes, it is important to state that the dropping-elec- 
trode experiments were performed in an atmosphere of 
hydrogen (cf §7, above). A piece of wide glass tubing- 
open at both ends encircled the dropping electrode, The 
lower end of this tube was immersed in the electrolyte, and 
the upper was closed by a rubber cork in which were three 
holes. The drop electrode passed through the central hole : 
the others served for the inlet and outlet of the hydrogen 
respectively. 
