488 Proceedings of Royal Society of Edinburgh. [sess. 
of a pipette and titrated as expeditiously as possible. The end point 
was determined in the same way after a sufficient time had elapsed. 
As it was not found possible to correctly titrate solutions contain- 
ing sulphuric acid and a neutral sulphate with baryta water, a 
solution of sodium hydrate was used, to which sufficient baryta 
solution had been added to precipitate the carbonate, with a slight 
excess. The concentration of the alkali was OT to 0*05 normal. 
Phenol-phthalein was used as indicator. 
THE VELOCITY CONSTANTS. 
(a) Sulphuric Acid and Potassium Sulphate. 
Three series of experiments were made with these solutions. 
In the first, the concentration of the sulphuric acid was varied, 
and that of the potassium sulphate was constant; in the second 
the concentration of the potassium sulphate was varied, and that 
of the acid remained constant. The third series was made with 
solutions containing equivalent quantities of the acid and neutral 
sulphate at varying dilutions. Each series consists of five different 
experiments. The constants were calculated according to the 
expression 
-i 1 i E 
* = 7- l0gl °E^’ 
where k is the velocity constant, t the time in minutes, x the 
quantity of acetic acid produced in time t , and E is the end-point. 
In the tables below the values of x and E — x are given in terms of 
the sodium hydrate solution. To avoid unnecessary ciphers the 
constants have been multiplied by 10 5 in every case. 
First Series. 
I. 
H 9 S0 4 0‘025 normal. 
K 2 S0 4 o-i 
t 
X 
E-a; 
tc 
984 
272 
1608 
6*96 
2366 
596 
1284 
7*00 
2800 
679 
1201 
6-95 
3764 
856 
1024 
7-01 
5271 
1070 
810 
6*94 
oo 
1880 
— 
6-96 
II. 
HoS 0 4 0’05 normal. 
k 2 ‘so 4 o-i 
t 
X 
E -x 
k 
177*5 
110 
1800 
14’5 
1209 
645 
1265 
14*8 
1604 
799 
1111 
14-7 
2621 
1127 
783 
14-8 
3028 
1225 
685 
14-7 
oo 
1910 
— 
14-7 
