112 Method of preserving the colour of the Purple Cabbage. 
In estimating these constituents according to the elec- 
tro-chemical theory, I believe that the oxide of titanium, 
notwithstanding its important agency in the analytical ex- 
periments, must be regarded as an accidental ingredient, 
as well as the oxide of iron, which in some measure may 
have been derived from the iron mortar. As the cymo- 
hane of Brazil appears to be constituted more conforma- 
bly to the hypothesis of chemical proportions than that of 
addam, the following calculation may be made, founded 
on its composition, which gives for the essential constitu- 
ents of Chrysobery], 
(Per 100 parts) 
Silica 661 containing Oxygen 3.32 
Alumina | 75.75 35.38 
Glucina 17.64 5.49 
and very nearly corresponds with the following mineralo- 
gical formula, A*S+2GA‘. 
Art. VII.—.Method of preserving the color of the pur 
cabbage. Extract of a letter to the Editor, from Geor 
T. Bowen. 
substances, the cabbage liquor is superior to litmus, for 
it is not only like litmus reddened by acids, but is also 
color by means of an alkali; and the delicacy of the test 
is in this manner impaired. I find that this test may be 
