AN ANIMAL PIGMENT CONTAINING COPPER. 
525 
i. 
ii. 
Turacin taken, dried at 100° C. 
Total ash obtained. 
’Turacin taken, corrected for ash. 
Copper, volumetrically determined .... 
Copper oxide, gravimetrically determined . 
Copper, gravimetrically determined .... 
gnu. 
•4627 
'0454 
'4581 
•0322088 
•0413 
•03297 
grin. 
•6832 
•066 
•6764 
•0464738 
•0588 
•046936 
These results correspond to the following percentages :— 
Total ash . . 
i. 
9 81 
ii. 
9 66 
Ash other than CuO ....... 
10 
109 
Copper, volumetrically determined . 
7-03 
<•'87 
Copper, gravimetrically determined . 
779 
6'94 
In the above calculations it has been assumed that the proportion of adventitious 
ash in turacin amounts to 1 per cent. This figure has been amply confirmed by other 
determinations, and has been adopted throughout the present paper as a correction. 
The mean corrected percentage of copper in turacin, as deduced from the four 
determinations just given, is 7'01.' 5 ' This figure, which corresponds to 8'79 per cent, 
of CuO, though higher than that obtained in my early experiments, is lower than that 
found by Mr, H. Bassett, t who by incinerating turacin with nitre and sodium car¬ 
bonate obtained, in two analyses, oxide of copper equal to 7’6 and 8'0 per cent, of the 
metal. As no correction was made for ash these numbers are probably 1 percent, below 
the truth, and may be safely taken to correspond to a mean percentage of 778. Now 
this number is confirmed by a determination which I made so long ago as September 14, 
1874. The turacin employed was prepared from Turacus corythaix, and was 
purified and dried in the usual way. It was oxidised by long warming with con¬ 
centrated nitric acid in a flask. The solution became at last of a clear green 
colour; it was cautiously evaporated to dryness and the residue incinerated. The 
residue was treated with nitric acid, and the solution filtered to remove a trace of 
silica. Finally the copper was precipitated hy caustic potash and weighed as oxide. 
The figure obtained was :— 
* In another experiment ’2318 grin, turacin, oxidized by repeated treatments with fuming nitric acid, 
gave, by Brown’s thiosulphate method, 6‘87 per cent, of copper—a figure which when corrected for ash 
becomes 6'94 per cent. During the progress of this analysis and of another determination made in the 
same way, it was observed that turacin, if treated at first with an insufficient amount of nitric acid, 
yields an intermediate product having a “ beetle-wing” lustre, and very difficult to oxidise by subsequent 
treatment with fresh portions of acid. 
t ‘ Chemical News,’ vol. 28, p. 201 (1873), 
