PHYCOERYTHRIN 355 



4. Caustic soda or potash in small quantities causes the 

 red colour to disappear, the solution turning opalescent and 

 yellowish-brown in colour ; on standing, a brownish precipitate 

 comes down. 



5. The solution is immediately decolorized by bleaching 

 powder, bromine water or a solution of iodine in potassium 

 iodide. 



6. Mercuric chloride solution in small quantities gives a 

 lilac-grey precipitate, the solution then being yellowish in 

 colour. 



7. Ferric chloride gives a pinkish-brown precipitate. 



8. Boiled with nitric acid a yellow colour results which 

 turns to orange on adding an excess of ammonia. 



9. Boiled with Millon's reagent a deep red colour results. 



10. The addition of a caustic soda solution followed by 

 a drop or two of dilute copper sulphate gives a greenish 



tint. 



11. Digestion with pepsin, in the presence of hydrochloric 



acid, has no result. 



12. On digestion with trypsin in the presence of sodium 

 carbonate, the phycoerythrin loses its colour, and the solution 

 contains a very small amount of leucin, but no tyrosin. 



13. On hydrolysis with acids, tyrosin is found in very 

 small amounts, but leucin occurs in greater quantities. 



From these and other facts it is concluded that phycoery- 

 thrin is a colloidal nitrogenous substance alhed to the proteins ; 

 it is not a true protein, since its nitrogen content is too low and 

 it does not give the biuret reaction. It is impossible to say 

 anything more definite regarding its chemical nature until it 

 has been prepared in a pure state in quantities sufficient for 

 analysis. 



According to Kylin,* phycoerythrin, separated from Cer- 

 amium rubrum, is made up of two constituents, a protein com- 

 bined with a colouring matter which can be hydrolysed by 

 acid or by alkali. 



Physiologically, phycoerythrin acts as a pigment com- 

 plementary to chlorophyll. It absorbs the blue-green rays, 



* Kylin : " Zeit. physiol. Chem.," 1910, 69, 169 ; 1912, 66, 82. 



23 * 



