Obervations on Phycoerythrin. 337 
OBSERVATIONS ON PHYCOERYTHRIN, THE RED 
PIGMENT OF DEEP-WATER ALGJE. 1 
By E. K. Hanson. 
[Plate V.] 
I ^HE red colouring matter of deep-water algae possesses con¬ 
siderable interest, especially in regard to two points :— 
1. Its role in assimilation. 
2. Its chemical nature, suggested to be protein. 
These problems have not been satisfactorily settled, and the 
following investigation was therefore undertaken to obtain some 
light, if possible, on these matters. 
Very great difficulty has been encountered, however, in the 
preparation of material. The colouring matter occurs in very small 
proportion in most of the red algae, and those which yield any 
reasonable quantity are only to he obtained under favourable tidal 
conditions in very few localities in the British Isles. Various species 
of Ceraniium, especially Ceramium rub rum, alone of the weeds used, 
gave a fair quantity. 
In addition, the pigment is soluble only in water, and the 
aqueous extract contains gummy substances from which it is 
necessary to purify the colouring matter, as far as possible, for 
chemical investigation. As the phycoerythrin on precipitation 
passes very easily into an irreversible “ gel,” the method of repeated 
re-solution and re-precipitation for purification is not practicable. 
The precipitate is also extremely difficult to filter, filtration being 
extremely slow even under pressure, so that prolonged exposure to 
the precipitant is unavoidable, and this exposure appears to 
accelerate the formation of the irreversible gel. Attempts were 
made to avoid this effect by keeping the filtering solutions at 0°C 
by means of an ice-jacket, but though this cooling delayed the 
formation of insoluble gel, it did not prevent it. 
The solid material used for the experiments below was therefore 
obtained by fractional precipitation with alcohol, but it can only be 
regarded as a very rough approximation to the pure colouring 
matter : as will be seen it contains a high percentage of ash. 
The weed was gathered and despatched to me with the least 
possible delay, and on arrival was immediately washed free from 
1 A short account of these observations was given to the Chemical 
Society, and an abstract has been published. Proc. Chem. 
Soc., 1909. 25. 117. 
