CHEMICAL BASIS OF THE ANIMAL BODY. 1171 



4. When precipitated from its acid solution by neutraliza- 

 tion the precipitate is more gelatinous than that of the other 

 acid-albumins, and less readily soluble in alkalis. 



3. Alkali-albumin. 



If serum- or egg-albumin or washed muscle be treated with 

 dilute alkali instead of with dilute acid, the proteid undergoes 

 a change in many ways similar to that which was brought about 

 by the acid. The alkaline solution, when the change has be- 

 come complete, is no longer coagulated by heat, the proteid 

 is wholly precipitated on neutralization, and the precipitate, 

 insoluble in water and in neutral solutions of sodium chloride, 

 is readily soluble in dilute acids or alkalis. 



Alkali-albumin may be prepared by the action not only of 

 dilute alkalis but also of strong caustic alkalis on native albu- 

 mins as well as on coagulated albumin and other proteids. The 

 jelly produced by the action of caustic potash on white of egg 

 (p. 1168) is alkali-albumin; the similar jelly produced by-strong 

 acetic acid is acid-albumin. In short the general statement 

 may be made that under otherwise similar conditions, if an 

 alkali is employed instead of an acid to act on proteids, alkali- 

 albumin is formed instead of acid-albumin. 



Notwithstanding their very similar general reactions acid- 

 and alkali-albumin are distinct, though very closely allied sub- 

 stances, and we might go even so far as to say that probably 

 every proteid yields its own kind of either the one or the other 

 proteid on treatment with acids and alkalis. But as yet we do 

 not possess any means of ^distinguishing between the several 

 forms of each substance by any ordinary reactions. 



The chief evidence which is advanced as to the difference 

 of the two products is the following. 



1. Alkali-albumin is in general more soluble than acid- 

 albumin. 



2. When precipitated by neutralization the former (alkali) 

 is flocculent, the latter (acid) is more viscid, transparent, and 

 gelatinous. 



3. When dissolved in a minimum of alkali and heated to 

 100 in sealed tubes, alkali-albumin coagulates, acid-albumin 

 does not. 



4. Alkali-albumin possesses, strongly marked, the proper- 

 ties of an acid. 



5. Acid-albumin can be converted into alkali-albumin by 

 the action of strong alkalis, but the reverse conversion of the 

 product thus obtained or of an ordinary prepared alkali-albumin 

 into auid-albumin is stated to be impossible. 



