658 
Proceedings of the Royal Society of Edinburgh. [Sess. 
The constant obtained in this way agrees fairly well with that obtained 
J, 
from the ordinary catalysis of methyl acetate by anthranilic nitrate ^ = 126. 
As another means of determining the hydrolysis of anthranilic hydro- 
chloride, the hydrion concentration in its solution was estimated by the 
electro -motive force method. The difference of potential between a hydrogen 
electrode immersed in the solution and a normal calomel electrode was 
measured. Then a solution of hydrochloric acid giving nearly the same 
E.M.F. was substituted for the hydrochloride, and the hydrion concentration 
c 
in the latter calculated from the formula d — ' 0572 log , where c is the 
C 2 
hydrion concentration of the two solutions, and d the difference between 
the observed electro-motive forces.* 
A moving-coil galvanometer with mirror and scale was used as zero 
instrument, and by an arrangement of resistances at each end of a metre 
bridge the length of wire available for measurement was about 10 metres. 
The solutions whose difference of potential was being measured were 
immersed in a thermostat at 25° C., and were connected by side tubes 
dipping into saturated ammonium nitrate solution. This has been found 
by Gumming f to be the most effectual eliminator of liquid surface potential. 
The hydrogen used was generated from zinc and sulphuric acid, passed 
through permanganate acidulated with sulphuric acid, and then washed 
with pure water. It was led into the liquid in the cell through the rubber 
stopper, and the excess escaped by a side tube with a water-trap. 
The hydrogen-platinum electrode was prepared by coating a glass tube 
with a film of burnt-in platinum, which was then lightly platinised. 
The hydrogen had to be passed through the liquid for about twenty 
minutes before the E.M.F. exhibited any degree of constancy. The current 
was then stopped and a reading immediately taken, the stream of hydrogen 
again passed for five minutes and another reading taken, and so on till the 
E.M.F. did not vary more than '2 of a millivolt. 
The potential of a normal calomel electrode was taken in this way 
alternately against hydrochloric acid and anthranilic hydrochloride solu- 
tions. After every reading of the unknown E.M.F., that of a standard 
cadmium cell was measured. 
Jc . . . 
The values for obtained in this way are seen to agree fairly well 
Iv 
with the results of catalysis experiments. 
* Nernst, Zeit. Physikal. Ghem., vol. iv. p. 129 (1889). 
t Trans. Faraday Soc., ii. p. 213 (1907). 
