STUDIES OF DIFFUSION THROUGH RUBBER 



MEMBRANES 



3. Diffusibility of protein through rubber membranes, with a 



note on the disintegration o£ coUodion membranes 



by common ethyl ether and other solvents 



WILLIAM H. WELKER 



(Biochemical Laboratory of Columbia University, at the College of Physicians 



and Surgeons, New York) 



l. INTRODUCTION 



In the course of our studies of proteins, under the auspices of the 

 George Crocker Special Research Fund, we obtained a protein 

 product which is soluble in a mixture of equal parts of absolute 

 alcohol and absolute ether, and which responds to the biuret, xantho- 

 proteic, Millon and Hopkins-Cole tests. The material was prepared 

 by the following method : 25 grams of Witte peptone were dissolved 

 in 500 c.c. of 0.2 per cent. hydrochloric acid Solution. The liquid 

 was evaporated to a thick syrup on a water bath. This syrup was 

 thoroughly extracted with absolute alcohol and the resultant yellow 

 liquid filtered. The filtrate was treated with an equal volume of 

 absolute ether, which produced a white flocculent precipitate. After 

 the Sedimentation of the precipitate, the supernatant liquid was de- 

 canted and filtered. When five volumes of absolute ether were 

 added to this filtrate, a white flocculent precipitate was produced. 

 This product was isolated by filtration, washed with absolute ether, 

 and exposed to the air in a thin layer on a watch glass, where it 

 solidified as yellowish and somewhat hygroscopic granulär material, 

 which could easily be pulverized. The product dissolved promptly 

 in absolute alcohol. From concentrated alcoholic Solution the prod- 

 uct may be precipitated by the addition of an equal volume of abso- 

 lute ether. Whether the product is peptone or a much simpler Poly- 

 peptid has not yet been determined. 



Dr. Gies and his collaborators have lately given much attention to 



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