ELISHA MITCHELL SCIENTIFIC SOCIETY. 5 
fo00:70': to 67.77; to 68.74; to 70.79; to 75.72. From 
this it is seen that the change begins at less than 30°, 
and from this arises the observation that has been made 
that the solution of the alum turns somewhat green at 
ordinary temperatures. 
The diffusion of these solutions has also been carefully 
studied with a view to throwing light upon this puzzling 
problem. 
With regard to the sulphate it has been shown by van 
Cleeff! that green solutions on being dialyzed yield dia- 
lysates containing a larger proportion of acids. This had 
been repeatedly investigated in the case of the alum. 
Thus van Cleeff has found that in the dialysis of the 
ereen solution of the alum, relatively more sulphuric acid 
goes into the dialysate than when the violet solution is 
dialyzed. Dougal’ has also carried out careful expert- 
ments along this line. ‘Time, temperature, strength of the 
dialysate, amount of initial change, amount of retrogres- 
sion, all affected the results, and little beyond the facts 
stated above could be deduced from them. The experi- 
ments were made upon solutions containing one per cent. 
of the alum. While the author states that no compari- 
son could justly be made between the experiments, it may 
be noted that the ratio of increase in acidity was fairly 
regular and ranged between one-seventh and one-sixth. 
A few experiments were undertaken upon the dialysis 
of the alum before Dougal’s experiments were known to 
us. They were not pushed to completion when these lat- 
ter became known, especially as there seemed little 
chance of their throwing much light upon the nature of 
the change. 
CHANGES IN CHEMICAL PROPERTIES. 
One of the most singular changes in chemical proper- 
tT]. prakt, Chem. (2), 23, 58. 
2]. Chem. Soc. Lond., 2896, 69, 1527. 
