28 ON SULPHATE OP POTASH. 
of carbonate of soda than in distilled water ; he also 
observes, that " every chemist will smile when he is in- 
formed that sulphate of potash might be decomposed by 
carbonate of soda." 
The opinions thus expressed are so much at variance, and 
the experiments by which the questions at issue may be 
determined, are so simple and easy of execution, that there 
would be no excuse for our remaining in doubt with regard 
to them, especially as they are considered to have some 
bearing upon the safety of the administration of a some- 
what popular remedy. Moreover, it is desirable that 
every pharmaceutist should be capable of determining 
points of this description, both for his own satisfaction and 
for the information of others. I propose, therefore, in 
giving the result of my experiments, to describe the man- 
ner in which they were performed, and to point out the 
precautions which are necessary in order to arrive at cor- 
rect results. 
The specimen of sulphate of potash employed in these 
experiments, was in well-defined crystals, which formed a 
clear solution in water. This solution was neutral to litmus 
paper ; and, on being tested with sulphuretted hydrogen, 
nitrate of silver, and the usual tests for the presence of 
nitrates, afforded no indications of impurity. 
Exp. 1. — To determine the degree of solubility of this 
salt, a portion of it was reduced to fine powder, and sixty 
grains of this was put into a vial, furnished with a good 
cork. This was now accurately counterpoised in the 
balance. A pneumatic trough, containing about a gallon 
of water, at a temperature of 60° Fahr., was provided, and 
this water was kept constantly at the same temperature. 
Distilled water was now added to the salt contained in the 
vial, the solution of which was promoted by agitation, 
while the temperature was regulated by [the immersion of 
the bottle in the pneumatic trough. When the salt was 
