Observations on Phycoerythrin. 343 
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(4) . Caustic soda or potash causes, even in small quantities, 
a complete disappearance of the rose colour, leaving a yellow-brown 
very opalescent solution, which, on standing, gives a brownish 
precipitate. 
(5) . Sodium bicarbonate and ammonium carbonate produce no 
effect, even after long standing. 
(6) . Bleaching powder solution, bromine water and iodine in 
potassium iodide solution decolorise at once without precipitating. 
(7) . A saturated solution of mercuric chloride, even in small 
quantities, produces a lilac-grey precipitate, and leaves an 
opalescent pinkish solution, which, after further addition of 
mercuric chloride solution and standing, gives a further dull grey 
precipitate, leaving a nearly clear slightly yellowish solution. 
An analysis of the first precipitate gave :— 
Weight of precipitate taken = 0-1663 gms. 
Vol. of N. at 17°C and 775 mm. was 6-6 c.c. 
Whence per cent. N. = 4-7. 
The precipitate gave qualitative reactions for mercury and 
chloride. 
(8) . Ferric chloride solution gave a pinkish-brown precipitate. 
(9) . Concentrated nitric acid, on boiling, gave a yellow colour 
deepened to orange by addition of excess of ammonia. 
(10) . Millon’s reagent, on boiling, gave a deep red colour. 
(11) . Caustic soda solution, followed by a drop of dilute 
copper sulphate solution, did not give either a violet or 
a pink colour, but a slight greenish tint. 
(12) . It is not abstracted from its aqueous solution by silk. 
Action of Proteolytic Ferments on Solution. 
(a). Pepsin. —0-1 gm. pepsin and I c.c. of “twice normal” 
hydrochloric acid were added to 50 c.c. phycoerythrin solution 
containing a trace of eucalyptus oil as antiseptic. A similar check 
experiment was performed using 50 c.c. of milk, also containing 
eucalyptus oil. The tubes were maintained at a temperature of 
33° to38°C in a water bath for forty-eight hours, but no change 
occurred in the phycoerythrin, whilst the casein in the milk 
(precipitated on adding the acid) had largely disappeared. 
Another sample of the same pepsin (0-2 gms.) in 40 c c. two 
per cent hydrochloric acid completely dissolved 0-2 gm. of hard- 
boiled white of egg in half-an-hour. 
(b .) Trypsin.—0-2 gms. sodium bicarbonate and 2 c.c. Lotio 
Pancreatis (Fairchild) were added to 50 c.c. phycoerythrin solution 
and a similar quantity of each to 50 c.c. milk and 10 c.c. of water. 
These tubes were kept at 33°—38° for forty-eight hours and tested 
