1898-99.] Sulphuric Acid and Sulphates in Solution. 497 
y. 
HC1 0 
*2 normal. 
HC1 0*2 normal. 
MgCl 2 
0*1 „ 
MgCl 2 0*2 
t 
X 
E - x 
Jc 
t 
X 
E - x 
Tc 
175 
444 
523 
152-5 
171 
433 
523 
153-2 
180 
450 
517 
151-0 
180 
452 
504 
154*5 
190 
467 
500 
150-7 
190 
470 
486 
154-7 
200 
481 
486 
149-4 
207 
499 
457 
154-9 
226 
527 
440 
151*3 
215 
518 
438 
157*7 
235 
543 
424 
152-3 
227 
531 
425 
155*1 
246 
558 
469 
152-0 
235 
547 
409 
156*9 
00 
967 
— 
151*3 
CO 
956 
— 
155*6 
In order to calculate from these experimental results, the real 
influence of the neutral salts on the velocity of reaction, the 
following consideration must not be neglected. The velocity with 
which an acid effects the catalysis is dependent on its degree of 
dissociation. In general, when a neutral salt is added to an acid, 
the degree of dissociation of the latter is changed, and therefore 
before comparing a constant obtained when a neutral salt is 
present, with that measured in the case of the acid alone, the 
value of the latter must be made equal to what would he found 
if the dissociation of the acid were the same as it is after the 
addition of the salt. An example will show how the correction 
was applied. 
The velocity constant for 0*2 normal hydrochloric acid, as ex- 
perimentally determined, had the value 146*9. When 04 normal 
sodium chloride was added, the constant obtained is 150*9. But 
by this addition of the neutral salt, the degree of dissociation of 
the acid is diminished from 0*896 to 0*882 (Arrhenius, Zeit. 
physikal. Chem 1888, ii. 286). The velocity constant with 
hydrochloric acid, dissociated to the latter extent only, is there- 
.009 
fore 146*9 x = 144*6. The true increase in the velocity of 
catalysis produced by the addition of 0*1 normal sodium chloride 
is now 150*9- 144*6 = 6*3, or 4*35 per cent, of the calculated 
value for hydrochloric acid (144*6). 
The results obtained for the different neutral chlorides em- 
ployed and calculated as above are exhibited in the following 
table : — 
