464 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Vitellin. 



Preparation. 



The precipitates of lecitho-vitellin obtained by either of the above 

 methods are treated with warm alcohol and ether. The lecithin is 

 dissolved and the vitellin remains. 



Since the protein of egg-yolk consists mainly of vitellin it can be 

 prepared directly from dried yolk (commercial or from yolks spread 

 out on a plate and allowed to dry in the air) by extracting them with 

 cold alcohol, hot alcohol and ether. The residue is vitellin, contain- 

 ing livetin and other constituents of yolk in small quantities. 



Properties. 



Vitellin forms a granular powder, which is pale yellow to reddish- 

 yellow in colour. It is insoluble in water and salt solutions ; also in 

 dilute acids ; it dissolves slowly in stronger acids undergoing hydrolysis. 

 It also dissolves sjowly in dilute alkali and probably undergoes 

 hydrolysis. It contains about I per cent, of phosphorus as shown by 

 incineration or other methods of oxidation (p. 30). The phosphorus 

 is split off by warming with dilute alkali in the same way as from 

 caseinogen (p. 461). 



Ichthulin. 



Phosphoproteins have been prepared from the eggs of various fish, e.g. 

 cod, carp and salmon. Like the vitellin from egg-yolk they seem to be in com- 

 bination with lecithin and are termed ichthulin. They have not been fre- 

 quently investigated. The phosphoprotein in sturgeon's egg is hydrolysed 

 by dilute alkali with the separation of inorganic phosphate. 



