OCR Text |
Show '875.] COLOURING O F B I R D S ' E G G S . 355 enable the alcohol to dissolve oorhodeine, the spectrum shows the five absorption-bands given in fig. l,and the general colour is brownish-red. This is the spectrum of the almost neutral modification when in a state of solution. W h e n in a free solid form, as in the shell, or as found in the washed dry skin-like residue after removing the carbonate 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 ot 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 oorhodeine. It is, however, 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. W h e n 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. Spectra of the oocyans, &c. 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 neutral alcohol, 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. 23* |