318 Intelligence and Miscellaneous Articles. 



a temperature of 86° to 95° Fahrenheit ; after some hours the liquid 

 is to be poured off, the membrane is to be again similarly digested, 

 and to be treated with cold water till it exhales a putrid odour ; it is 

 then to be filtered ; the filtered liquor is transparent, slightly viscid, 

 and exhibits a remarkable digestive power when a small quantity 

 of hydrochloric acid is added to it. In order to extract the pepsin 

 in a pure state, acetate of lead is to be added to this liquor ; the 

 precipitate is washed, diffused in water, and decomposed by a cur- 

 rent of hydrosulphuric acid. The filtered liquor is colourless, and 

 has an acid action, owing to the acetic acid. 



When this liquor is evaporated at 95° Fahrenheit, to the consist- 

 ence of a syrup, and absolute alcohol is added to it, an abundant 

 fiocculent precipitate is formed, which on drying leaves a yellow 

 gummy matter, which does not attract moisture, and is pure pepsin. 



This substance easily dissolves in water, and the solution, even 

 though it contains only 1-5000, dissolves slightly acidulated white 

 of egg, in about six or eight hours. The aqueous solution has an 

 acid action owing to some acetic acid which remains intimately 

 combined with it ; it cannot be separated from the pepsinate of lead, 

 even by repeated washings. By ebullition this liquor loses its di- 

 gestive powers. If the free acid which it contains is cautiously 

 saturated by potash, a small quantity only of which is requisite, 

 flocculi are deposited, and the digestive power is also lost. 



The alkalies cautiously added to the solution of pepsin, till the 

 free acid is saturated, occasion the formation of flocculi, and the li- 

 quor has no acid action. Sulphuric acid in small quantity "produces 

 white flocculi, which redissolve in a slight excess of the acid ; by 

 the addition of a further quantity, fresh flocculi are produced ; hy- 

 drochloric and nitric acids produce the same effects. 



Perchloride of mercury occasions a precipitate which is redis- 

 solved by an excess of it ; the proto- and persulphates of iron and 

 the sulphate of copper precipitate pepsin. Alcohol precipitates it 

 from a concentrated solution. According to M. Pappenheim, this 

 precipitate dissolves in hydrochloric acid, and dissolves boiled white 

 of egg. M. Wasmann confirms this statement of the digestive 

 power of the precipitate formed by alcohol, while, according to 

 M. Schwann, alcohol destroys the digestive property of pepsin. " 



Pepsin is recognized by the precipitates which its solution gives 

 with diluted acids, and which redissolve in an excess of the acids, 

 and by its giving no precipitate with ferrocyanide of potassium. It 

 is distinguished from albumen by the precipitates which its solution 

 yields on the addition of water and hydrochloric acid ; and from 

 caseum, by its acid solutions yielding no precipitate with ferrocy- 

 anide of potassium. — Journal de Chimie Medicale, Aout, 1840. 



DECREPITATING SALT OF WIELICZKA. BY H. ROSE. 



This salt was first noticed by M. Boue, who sent a specimen of it 

 to M. Dumas ; it is distinguished from common salt by decrepitating 

 not only when it is heated, but when dissolved in water ; during so- 

 lution decrepitation occurring with the disengagement of gas. It 

 is evident that this gas was confined in the salt in a state of strong 



