ELISHA MITCHELL SCIENTIFIC SOCIETY. 3 
further states that the crystals of potassium sulphate 
separate only from a highly concentrated solution and in 
small quantity. Sprung has shown, in experiments to 
be quoted later, that the change begins at a temperature 
under 30°. 
We have repeatedly attempted to secure the separation . 
of crystals of potassium sulphate as described by Fischer 
and Schrétter, but without success. The exact condi- 
tions are clearly difficult to hit upon, if such a separation 
is at all possible. 
Alkaline hydroxides and carbonates, according to van 
Cleeff,’ turn violet solutions of the alums green, and 
Etard’ has shown that they bring about the same change 
in solutions of the normal sulphate. Sulphuric acid, 
phosphorus trichloride, and nitric acid, according to 
Etard, bring about the same change, but Otto’ says that 
sulphuric acid does not turn solutions of the alum green 
if rise of temperature is prevented. Schrétter says that 
nitric acid turns green solutions of chromium sulphate 
blue again. 
Our experiments along this line resulted as follows: 
First as to the action of acids. Hydrochloric acid had 
no action upon either violet or green solutions, nor does 
it apparently have any influence upon the change from 
one to the other on heating. Sulphuric acid brought 
about no change in either in the cold, but has a retarding 
influence upon the change on heating. This was so 
marked in one or two experiments that 1t was thought 
the change would be entirely prevented. Nitric acid had 
no appreciable immediate effect upon either in the cold. 
On heating with the violet the retarding action was 
ereater than when sulphuric acid was used, and the solu- 
tien resumed its violet color on cooling. Acetic acid had 
1J. prakt. Chem. (2), 23, 58. 
2 Compt. rend., 84, 1090. 
3Graham-Otto, 4 Aufl., 3, 113, 
