16 JOURNAL OF THE 
On evaporating the liquid portions other masses were 
obtained. ‘These were also analyzed : 
Calculated for Found. 
2Cry(SO4)3.Cro(OH),.20H2O 1. II. III. 
Ree eieehs i ndnieces 22.70 22.93 22.71 22.98 
=) UN aS Ege ie, ey: 42.72 42.72 43.32 43.46 
sf ot I al a A ene a 34.57 
This is less basic than the previous compound. As the 
alcohol left is decidedly acid, it must contain either free 
acid or an acid sulphate. 
It did not seem to be necessary to prepare other chro- 
mium sulphates, as these experiments were in accord 
with those obtained with the alum, and lack of time made 
it necessary te bring the experiments to an end. 
CONCLUSIONS. 
On weighing the experimental evidence which has been 
brought to bear upon these changes, it is an easy matter 
to exclude some of the explanations offered. : Thus the 
dissociation of the alum into chromium and potassium sul- 
phates and similar theories which will not cover the ca- 
ses of the nitrates, chlorides, etc., must of course be 
dropped. The formation of chromo-sulphuric acid, as 
suggested by Recoura, is not tenable in the light of the 
experiments performed. The theory of the change of hy- 
dration is not satisfactory, since it has been seen that a 
loss of one-half the water did not bring about the change 
of color. 
The theory of Berzelius, however of the formation of 
basic salts of chromium which would naturaily be green 
and uncrystallizable, offers a full and sufficient explana- ' 
tion of the changes, and is in accord with the observa- 
tions so far as they have been verified by us. It accounts 
quite plausibly for the partial withholding of the sul- 
phuric acid from precitation by barium chloride in the 
cold, and is strongly confirmed by the experiments with 
alcohol. ‘This theory is also in accord with the facts that 
