126 THE PROTEIN SUBSTANCES. 



concentrated proteid solution, such as blood-serum or egg-albumin, the 

 alkali album inate may be obtained as a solid jelly which dissolves in 

 water on heating, and which is called " LIEBERKUHN'S solid alkali 

 albuminate." By the action of dilute caustic alkali solutions on dilute 

 proteid solutions we have alkali albuminates formed slowly at the ordinary 

 temperature, but more rapidly on heating. These solutions may vary 

 with the nature of the proteid acted upon, and also with the intensity 

 of the action of the alkali, but still they have certain reactions in common. 



If proteid is dissolved in an excess of concentrated hydrochloric acid, 

 or if we digest a proteid solution acidified with 1-2 p. m. hydrochloric 

 acid in the thermostat, or digest the proteid for a short time with 

 pepsin-hydrochloric acid, we obtain new modifications of proteid which 

 may show somewhat varying properties, but have certain reactions in 

 common. These modifications, which may be obtained in a solid gelat- 

 inous condition on sufficient concentration, are called acid albuminates 

 or acid albumins, and sometimes syntonin, though we perfer to apply 

 the term syntonin to the acid albuminate, which is obtained by extract- 

 ing muscles with hydrochloric acid of 1 p. m. 



The alkali and acid albuminates have the following reactions in 

 common: They are almost insoluble in water and dilute common-salt 

 solution (see page 104), but they dissolve readily in water on the addi- 

 tion of a very small quantity of acid or alkali. Such a solution as nearly 

 neutral as possible does not coagulate on boiling but is precipitated at 

 the normal temperature on neutralizing the solvent by an alkali or an 

 acid. A solution of an alkali or acid albuminate in acid is easily pre- 

 cipitated on saturating with NaCl, but a solution in alkali is precipitated 

 with difficulty or not at all, according to the amount of alkali it contains. 

 Mineral acids in excess precipitate solutions of acid as well as alkali 

 albuminates. The nearly neutral solutions of these bodies are also pre- 

 cipitated by many metallic salts. 



Notwithstanding this agreement in the reactions, the acid and alkali 

 albuminates are essentially different, for by dissolving an alkali albumi- 

 nate in some acid no acid, albuminate solution is obtained, nor is an alkali 

 albuminate formed on dissolving an acid albuminate in water by the 

 aid of a little alkali. In the first case we obtain a combination of the 

 alkali albuminate and the acid, soluble in water, and in the other case a 

 soluble combination of the acid albuminate with the alkali added. The 

 chemical process in the modification of proteids with an acid is essentially 

 different from the modification with an alkali, hence the products are 

 of a different kind. The alkali albuminates are relatively strong acids. 

 They may be dissolved in water with the aid of CaCOs, with the elimina- 

 tion of CO2, which does not occur with typical acid albuminates, and 

 they show in opposition to the acid albuminates also other variations 



