3898-99.] Sulphuric Acid and Sulphates in Solution. 521 
lithium respectively, may be represented in each case by an 
expression of the form 
{C r .H 2 SO 4 (l-a 1 )}0-85_ A 
gmhso 4 (i - a 3 ) { a.M 2 so 4 (i - a 2 )y 5 
where x is equal to unity when M is K, and equal to P35 when 
M is 1ST a or Li. The constant A has a characteristic value in each 
case, and in the expressions involving potassium, sodium, and lithium 
sulphates it is equal to 0-259, 0-0618, and 0*0600 respectively. 
The expression has been deduced quite empirically from the 
experimental results, and within the limits of the experiments it 
has been shown to give results which compare favourably with 
those actually observed. 
I hoped to be able to extend this investigation to determine the 
nature of the equilibrium in solutions of other acid sulphates, but 
did not succeed in finding a suitable indicator for the titrations, 
and was therefore unable to measure the velocity constants. 
Using litmus as an indicator, I made a few determinations with 
solutions containing sulphuric acid and ammonium sulphate, but 
the titrations were unsatisfactory and the results untrustworthy. 
They showed, however, that sulphuric acid has less action on 
ammonium sulphate than on the sulphates of the alkali metals. 
Percentage Acid Salt. 
0-35H 2 S0 4 + 0-1K 2 S0 4 15-10 
„ +0-lUa 2 SO 4 15-06 
„ + 0*lLi 2 SO 4 13-72 
„ +0-l(NH 4 ) 2 SO 4 12-62? 
It appeared from a few measurements, that the action of 
sulphuric acid is still less in the case of magnesium sulphate. 
Ostwald (Journ. prakt. Chem., 1879, xix. 483) determined 
approximately the amount of free acid in solutions of some acid 
sulphates by their action on zinc sulphide. Here, of course, the 
equilibrium is complicated and disturbed by the presence of foreign 
substances, and although the results differ considerably from those 
I have obtained, their arrangement in order of magnitude is 
the same. 
2 L 
VOL. XXII. 
21/4/99 
