AN ANIMAL PIGMENT CONTAINING COPPER. 
521 
position of the band is, I think, identical with that of the characteristic band (as 
figured in my previous paper) of “altered turacin,” and with the band of 
Krukenberg’s turacoverdin. But the band y is so much fainter and so much 
narrower than the bands in question, that it can betoken the existence of no more 
than a trace of an alteration-product in the carefully prepared sample of turacin with 
which the majority of the analyses here recorded were performed ; the presence of 
such a trace can scarcely have affected in an appreciable degree the figures obtained. 
In connection with the probable presence of traces of an alteration-product of turacin 
in solutions made from the isolated pigment it is important to compare the spectra 
6 and 7 in the cut, p. 519, they are virtually identical. There is no increase in 
the prominence of the suspicious y band in the spectrum of a solution of isolated 
turacin in ammonia water after the lapse of twenty-three years. The particular 
specimen of turacin solution examined had been kept in a white glass bottle nearly 
full, but from which the stopper had been several times withdrawn ; it had been 
exposed to moderately strong diffused daylight during fifteen years, but had been 
preserved in the dark for the eight years which immediately preceded its spectro¬ 
scopic examination. Such a result is in striking contrast with that which is obtained 
when turacin, precipitated in flocculi by an acid from an alkaline solution, is allowed 
to remain for some time in contact with distilled water and atmospheric air. The 
precipitate loses its red hue, becoming dull and dark at first, and then acquiring a 
decided green colour. The same changes occur when a red Touraco feather is 
repeatedly wetted with pure water and dried, or when a piece of paper, stained with 
an ammoniacal solution of turacin, is kept for some time under the varying conditions 
of ordinary atmospheric moisture. The green turacin derivative produced in these 
experiments shows the spectral band y with great distinctness, but it is always 
accompanied by the three bands proper to pure turacin in alkaline solution; this 
observation is true, even when every endeavour is made to complete the process of 
change. 
Although the two spectra of turacoporphyrin described at the beginning of this 
section closely resemble the spectra of hsematoporphyrin (obtained from hsematin bv 
the same treatment), yet the presence of a metallic constituent in the former 
derivative, and its absence from the latter is sufficient to prove that the two bodies 
are not exact analogues. 
§ 5. Nitrogen in Turacin . 
The production of the volatile derivative of turacin, when that pigment is strongly 
heated, is probably the cause of the difficulty experienced in determining correctly its 
percentage of nitrogen, this volatile product being formed in varying proportions, 
and being very difficult of combustion. The mean percentage of nitrogen given in 
my former paper was 6'38, a figure which, on a careful recalculation of the analytic 
data, comes out rather ower, and which was founded on three determinations by 
MDCCCXCII.—A. 3 X 
