Observations on Phycoerythrin. 341 
in nature. He supports this contention by the following observa¬ 
tions on phycoerythrin obtained by crystallisation from aqueous 
extract of weed. 
(a.) Phycoerythrin gives the Xanthoproteic reaction. 
(b) , Millon’s reagent gave a good result when applied to 
Phycoerythrin previously bleached by exposure to light. 
(c) . Phycoerythrin is soluble in water only. 
On the other hand, Molisch obtained “ weak reaction ” in the 
Biuret test. 
The facts seem insufficient to establish the protein character 
of phycoerythrin, and attempts have, therefore, been made to 
obtain more evidence. 
The chief difficulty lies in the purification of the phycoerythrin. 
It is quite easy to believe that there are protein-like substances in 
algae which are extracted by cold water, but is phycoerythrin itself 
one, or is it a non-protein colouring matter merely carried down in 
the precipitation of the colloidal bodies ? 
Experiments were first made to see whether such a dye as 
eosin was completely precipitated along with egg-white from 
aqueous solutions. Various proportions of eosin were used, and as 
eosin is similar in colour and fluorescence to phycoerythrin, 
approximate matches were obtained to different concentrations of 
phycoerythrin. The precipitant chosen was alcohol, and it was 
found that in no case was the whole of the colour precipitated 
with the egg-white even where the latter was in far greater con¬ 
centration than any albuminous substance in the algal extract. On 
the other hand, all the red colour could he precipitated from the 
Ceramium extract, leaving only a faint dirty-yellow opalescence. 
This seems to indicate that phycoerythrin is itself colloidal and 
precipitated by alcohol. 
Phycoerythrin also differs from dyes such as eosin in that 
it is not abstracted from solution by silk. 
Estimations of nitrogen have been made, but the results vary. 
It has been found that the quantity of mineral matter in the crude 
phycoerythrin, even when using the middle fraction, is always 
large. 
A few figures are given below. 
Results on first fraction precipitated (alcohol precipitant). 
(a). Weight of substance used, 0-0630 gms. 
Vol. of N. at 16°C and 771 mm. was 4-4 c.c. 
Whence per cent. N. = 8-27. 
