528 
PROFESSOR A. H. CHURCH ON TURACIN, 
Carbon 
Hydrogen 
Copper 
Nitrogen 
Oxygen , 
53-69 
4-60 
7-01 
6-96 
27-74 
It is somewhat rash to suggest an empirical formula for a body which can neither 
be crystallised nor distilled, and to which few of the ordinary criteria of purity can be 
applied. The experimental percentages do not agree closely with any formula in 
which the ratio Cu : N 4 occurs—a ratio which analogy with heematin (which has 
Fe : N 4 ) would lead one to prefer, but they do correspond very nearly with the 
following more complex expression 
Theory, C 82 H 81 Cu 2 N 9 0 32 . 
Experiment. 
Per cent. 
Per cent. 
C 8 , = 984 = 5378 
53-69 
H 81 = 81 = 4-43 
4-60 
Cu 2 = 126-6 = 6-92 
701 
N 9 =126 = 6-89 
6-96 
0 3 o = 512 = 27-98 
27-74 
The agreement of these theoretical and experimental numbers is satisfactory. 
Although I should have preferred a simpler empirical formula, and the atomic ratio 
between metal and nitrogen of 1 : 4 rather than the ratio 2 : 9, yet there exist two 
arguments in favour of a more complex expression. One of these arguments is based 
on the partial loss of copper which turacin suffers when strongly heated—a loss 
which seems to indicate that the whole of the copper present does not exist in the 
same state of combination. The other argument is founded on the partial retention 
of copper by turacoporphyrin. This shows that its formation does not proceed upon 
exactly the same lines as those of hsematoporphyrin, which retains none of the metallic 
constituent present in its parent-substance, hsematin. 
I wish it to be understood that I lay no stress upon the formula which I have 
suggested, regarding it merely as a mode of expressing the results of analysing a 
substance which I believe to be constant in composition and very nearly pure. And, 
in the absence of sufficient data of control, I do not think it worth while to compare 
the experimental percentages with those demanded by such simpler formulae as— 
C^H^CuN^o; C 40 H 40 CuN 4 O 15 ; C 40 H 38 CuN 4 O 16 ; and C 40 H 38 CuN/) 15 . 
§ 9. Summary and Conclusions. 
The more important positions established by the present research are these : — 
I. The constant occurrence, in 18 out of 25 known species of Musophagidae, of a 
