300 Mr Hopkins, On the Separation of 



On the Separation of a pure Albumen from Egg-white. By 

 F. Gowland Hopkins. 



[Bead 19 February 1900.] 



A very important service to the chemical study of animal 

 proteids was rendered by Hofmeister's discovery, that egg- 

 albumen can be obtained in crystalline form when its solutions 

 are evaporated in the presence of ammonium sulphate. Hof- 

 meister's observation was made in 1890 x , and it was shortly 

 afterwards shown by Giirber 2 that albumens from the blood 

 serum of horses and rabbits also assumed a crystalline form 

 under like treatment. 



These observations made it reasonable to hope that material 

 for chemical study could be thus obtained for which there would 

 be some guarantee of chemical purity. But the crystalline pro- 

 ducts obtained by Hofmeister's process directly from egg-white 

 or serum are almost certainly not chemical individuals. Thus 

 in the case of the egg-proteid Bondzynski and Zoja 3 prepared 

 various crystalline fractions, and found rotatory powers for these 

 which varied from — 25°'8 to — 42 n, 54, and I have myself repeat- 

 edly observed that more than one albumen separate in crystalline 

 form. 



Any attempt to fractionate out a product of constant rotatory 

 power proves very laborious and involves much loss of material. 



About a year ago I described, in conjunction with Dr S. N. 

 Pinkus 4 , a method of crystallizing albumens, which, while involving 

 only a slight modification of Hofmeister's process, makes it possible 

 to obtain products with extreme ease and rapidity. By a further 

 modification of this method I believe it is possible to arrive with 

 little trouble, at an albumen well characterised as a chemical 

 individual. 



For this purpose egg-white is intimately mixed with an equal 

 bulk of saturated ammonium sulphate solution, and the mixture 

 is filtered. The filtrate, which is alkaline with ammonia (liberated 

 by the fixed alkali of the native proteid) is carefully neutralised 

 by means of dilute (10 °/ ) acetic acid, further acid being after- 

 wards added till one part per mill, of acetic acid is present. A 

 precipitate separator which, though at first amorphous, becomes 

 rapidly crystalline on standing. After a few hours, microscopical 



1 Zeitsch. f. physiol. Chem. xiv. s. 165. 



2 Sitzungsb. d. phys.-med. Gesellsch. zu Wilrzburg, 1894. 



3 Zeitsch. f. physiol. Chem. 1894. 



4 Journal of Physiol. 1894. 



