320 CHEMISTRY OF THE PROTEIDS CHAP. 



What salt one uses for precipitating acid-albumins does not seem 

 to be of much consequence, if one were to believe the accounts 

 generally given. Billow has observed, however, differences between 

 the an-ions. 



The conditions influencing the precipitation of the alkali-albuminates 

 are even less understood, for the precipitation due to the addition of 

 larger amounts of sodium chloride has to compete with the formation 

 of the slightly soluble albuminate of calcium. In this special case the 

 nature of the base plays therefore a great part, but even the ex- 

 haustive researches of Pauli l have not been able to clear up the 

 matter. Pauli sums up his results thus : The change in the coagulation- 

 temperature of albumins depends on the added effects of the two 

 independent ion-actions, each kind of ion possessing, for nearly every 

 salt, its zone of maximal action. In the case of a single salt its action 

 on the albumin may be so pronounced within a certain zone that the 

 addition of other salts produces no further effect. Thus NaCl within 

 certain limits is practically not affected by the addition of any quantity 

 of NaN0 3 . If two different acid or metallic ions are present it is 

 impossible to predict the result on the coagulation-temperature, as 

 much depends on the nature of the ions ; but the result generally 

 depends on the effect of one salt predominating within certain 

 concentrations, and then the other salt, if present up to a certain 

 minimum, may be increased five- or sixfold. Sodium chloride 

 and sodium nitrate show two such phases one for either salt, while 

 the mixtures of NH 4 Br and NH 4 C1 or MgCl 2 and NaCl show only 

 one phase. 



That albumin coagulates while albumoses do not, Pauli ascribes 

 to the presense of several albumose radicals in each albumin molecule, 

 or to a special kind of unison between the albumose -groups in the 

 albumin ; and he believes the ions of a salt during heat coagulation 

 to attach themselves, more or less firmly, to different parts of the albu- 

 mose radicals. Spiro 2 has found that inorganic bases (cholin, pyridin, 

 anilin, piperidin, ortho-toluidin, xylidin), and even the feebly basic 

 urea, thio-urea and urethan form alkali-albuminates, 3 and that for this 

 reason they keep denaturalised albumin in solution. Eamsden's 4 

 observations on urea are also very interesting. Plurivalent alcohols, 

 glycerine, carbohydrates, esters, ketones, and aldehydes have a similar 



1 W. Pauli, Pjiilger's Arch.f. d. ges. Physiol. 78. 315 (1899). See Mann's Physio- 

 logical Histology, pp. 60-65. 



2 K. Spiro, Zeitschr. f. physiol. Chem. 30. 182 (1900). 



3 Renard, Journ. of Physiol. Proceed, xxviii. 23. (1902). 



4 W. Ramsden, Journ. of Physiol. Proceed. 28. 23 (1902). 



