Robertson. — A Pigment in Oysters. 



247 



Art. XXXI. — On a Pigment in Oysters. 

 By G. H. Robertson, M.Sc. 



[Read before the Otago Institute, 7th October, 1913.] 



The existence in the Stewart Island oyster of a pigment with a distinct 

 absorption spectrum has already been recorded by J. Malcolm.* This 

 investigator noticed that when dried oyster was extracted with ether, 

 chloroform, benzene, or other fat-solvent a solution was obtained which 

 gave a single, band in the red — nearer the infra-red than the characteristic 

 methaemoglobin band. The pigment was found in all the samples examined. 



The present investigation was directed towards mapping out the varia- 

 tion of the spectrum with dilution, and the reactions of the pigment, with 

 a view to placing it in one of the known classes of animal pigments. 



Of all solvents, the pigment was found to be most soluble in ether, and 

 accordingly this solution was used for spectroscopic examination. The 

 results of this examination will be seen in the accompanying figure. 



At the highest concentrations obtained two bands are seen, both in the 

 red. As the dilution increases, a band appears in the blue-green about the 

 neighbourhood of the E line. At a slightly greater dilution the broad band 



Graphic Representation of the Variation in the Absorption Spectrum 

 of Solutions of Oyster Pigment with Changing Dilution. 



at the red end splits into two, and now over a considerable range of dilu- 

 tion four bands are visible. At greater dilutions the various bands dis- 

 appear, as shown in the figure, which is drawn accurately to scale. The 

 band in the red, between the B and C lines, persists long after the other 

 bands have all been lost sight of. This is probably the band observed by 

 Malcolm. 



Chemically the pigment is characterized by its great stability. Alco- 

 holic or alcohol-ether solutions were used, and when the addition of the 

 reagent caused no change in the position of the bands it was presumed 



* Trans. N.Z. Inst., vol. 44, 1912, p. 265. 



