508 Proceedings of Royal Society of Edinburgh. [sess. 
h 2 so 4 
First Series. 
k 2 so 4 
A 
0-025 
rH 
O 
+ 
0-250 
0*05 
9 9 
0-244 
0*1 
9 9 
0-242 
0*2 
9 9 
0-279 
0*35 
9 9 
0-277 
Mean value of A = 0‘252. 
h 2 so 4 
Second Series. 
k 2 so 4 
A 
0*1 
+ 0-4 
0-292 
99 
0-2 
0-242 
99 
o-i 
0-242 
9 9 
0-05 
0-262 
9 9 
0*025 
0*265 
Mean value of A = 0-265. 
h 2 so 4 
Third Series. 
KoS0 4 
A 
0*2 
+ 6-2 
0*244 
0*15 
0-15 
0-254 
0*1 
o-i 
0*242 
0-05 
0-05 
0*300 
0*025 
0-025 
0-324 
Mean value of A = 0 *260. 
The steady rise in the value of the constant which was apparent 
when the calculations were made with the previous expression for 
the equilibrium, has now to a large extent disappeared, and in 
each series the constant fluctuates about the mean value. In 
examining the constancy of A it must be remembered that the 
percentage of free acid in any solution is the quotient of two 
velocity constants, and as the experimental error may have the 
opposite sign in these two constants, the corresponding error in 
the percentage of free acid may be considerably increased. 
Further, this error is much exaggerated in the constant A, as 
for example, in one experiment an error of 1 per cent, in the per- 
centage of free acid produces a change of 22 per cent, in A. 
This, however, is the worst case, as may be seen by inspection of 
the “ weights ” given to the individual constants. 
The mean value of A for all three series is 0259, the greatest 
difference between this and any of the mean values obtained from 
each series separately being less than 3 per cent. In view of the 
fact [that the method of calculation emphasises the errors of 
individual experiments, this will be accounted fairly satisfactory. 
