1875.] COLOURING OF BIRDS’ EGGS. 355 
enable the alcohol to dissolve oorhodeine, the spectrum shows the five 
absorption-bands given in fig. 1, and the general colour is brownish- 
red. This is the spectrum of the almost neutral modification when in 
a state of solution. When in a free solid form, as in the shell, or as 
found in the washed dry skin-like residue after removing the car- 
bonate of lime by an acid, the spectrum is most materially different, 
as will be seen from the woodcut. Only three bands are distinctly 
visible, and they lie nearer to the red end, whilst there is far more of 
general absorption at the blue end. The result of this is that the 
general colour is a peculiar brown-red. 
Oorhodeine is of such a very permanent character that it resists 
the action of very powerful reagents. I have been able to destroy it, 
but have not yet succeeded in changing it into any other coloured 
substance. 
2. Oocyan.—In most cases this is readily soluble in neutral 
alcohol, and can thus be separated from oorhcdeine. It is, how- 
ever, often associated with yellow substances that cannot easily be 
removed ; very commonly, therefore, the solution is of a somewhat 
green-blue colour, but in many cases the yellow impurity is far 
more easily decomposed by the action of light or by weak oxidizing 
reagents, and can be removed by this means, so as to enable us 
to determine the true colour and spectrum of the oocyan itself. 
When dissolved in alcohol, it is of a very fine blue colour. The 
spectrum shows no detached bands, but a strong general absorption 
of the entire red end and of a small portion of the extreme blue, 
as shown in fig. 2. 
Fig. 2. 
400 
Oocyan. 
Banded 
oocyan. 
Product of 
their oxidi- 
zation. 
Spectra of the oocyans, Ke. 
3. Banded Oocyan.—This also is of fine blue colour, but differs 
from the former species in giving a spectrum with a well-marked 
detached absorption-band near the red end, as shown in fig. 2. 
It is also far less soluble in neutral alcohol, so that it is left in the 
shell-residue after having been digested for some time in cold neu- 
tral aleohol, and can subsequently be dissolved out by alcohol, to 
which a minute quantity of hydrochloric acid has been added. The 
solution must, however, be examined at once, since banded oocyan 
is rapidly decomposed by strong acids. ~~ 
