1032 PEPSIN, GLOBULIN, &C. 



to a fresh solution of pepsin 1 or 2 volumes of strong alcohol, 

 the pepsin is precipitated in white flocks which may be collected 

 on a filter. The alcoholic liquid filtered, gives on evaporation 

 a brown deliquescent residue, which reddens litmus and is 

 entirely deprived of digestive powers. 



The precipitate of pepsin forms white flocks, which, upon 

 drying on the filter, produce a grey compact mass. When 

 moistened with water, it swells up and dissolves in a large 

 quantity of water. It dissolves more easily in water acidulated 

 with acetic or any other acid ; this solution is not disturbed 

 by ferrocyanide of potassium, and possesses in a high degree 

 the power of dissolving coagulated albumen. A solution of 

 dried pepsin in pure water is rendered turbid by ebullition., 

 and loses its solvent power for aliments. 



Many metallic salts precipitate pepsin, although not entirely, 

 from a fresh solution of the membrane ; such as protosulphate 

 of iron, sulphate of copper, acetate of lead, chloride of mercury 

 and protochloride of tin. Pepsin may again be separated from 

 these precipitates by exposing them suspended in water to a 

 stream of sulphuretted hydrogen ; but a portion of the acid of 

 the metallic salt remains in combination with the pepsin, forming 

 a compound which has a well marked acid re-action on litmus, 

 and possesses the solvent powers of pepsin in a high degree. 



Acetate of pepsin may be obtained by decomposing the 

 precipitate obtained with acetate of lead, by means of sulphu- 

 retted hydrogen, then evaporating the solution of pepsin with 

 caution to a syrupy consistence, and treating it with alcohol. 

 The acetate of pepsin remains undissolved by the alcohol, in 

 the form of white flocks, which become a mass, on drying in 

 the air, resembling gum. It does not attract humidity, but 

 dissolves easily in water, with an acid reaction. A solution of 

 the dried acetate in 60,000 times its weight of water, to which 

 a little hydrochloric acid is added, dissolves white of egg in 

 the course of six or eight hours. Alkalies appear to destroy 

 the specific solvent power of pepsin. 



Hydrochlorate of pepsin is obtained on precipitating the 

 infusion of the mucous membrane by chloride of mercury, de- 

 composing the precipitate, after being well washed, by sulphu- 

 retted hydrogen, and mixing the filtered liquid which contains 

 the pepsin with alcohol, by which the hydrochlorate of pepsin 



