DENATURIZATION. 31 



Spiro has demonstrated that the temperature of coagulation is 

 materially influenced by the presence of certain nitrogenous bodies, 

 such as cholin, piperidin, pyridin, and anilin, which are all capable 

 of preventing the coagulation of a certain amount of albumin. Urea 

 is even more active in this respect, and when present in sufficient 

 concentration may prevent coagulation altogether. A similar effect 

 is produced by the mustard oils. 



Formerly the separation of the different albumins from each 

 other and their identification by fractional coagulation was ex- 

 tensively employed, while at present the method has fallen some- 

 what into disfavor. This is largely owing to the observation that 

 the temperature of coagulation may vary within fairly wide limits 

 with the amount of salt present and the reaction. It is to be noted, 

 however, that with constant conditions as regards these two factors, 

 and especially in reference to the reaction, the result also will be 

 quite constant. To insure complete precipitation, the reaction 

 should be just acid ; if this point has been attended to, the amount 

 of salt is of secondary importance, providing that not too little is 

 present. In any event, in reporting results it is well to note the 

 concentration of the albuminous solution, the strength of the salt 

 solution, and the reaction, together with the temperature of coagu- 

 lation. 



Denaturization. It has been pointed out that heat coagulation 

 alters the character of all true albumins in such manner that they 

 lose their common properties and are no longer soluble in the usual 

 neutral media. Neumeister has termed the change denaturization 

 of the albumins. This change can also be brought about by other 

 means than heat, such as precipitation with acids, the salts of the 

 heavy metals, the various alkaloidal reagents, shaking with chloro- 

 form or ether, alcohol, aceton, and even by prolonged standing. 

 Coagulation is not an essential phase of denaturization. Denaturi- 

 zation may indeed become manifest by the non-occurrence of coagu- 

 lation. This occurs upon the addition of metallic silver or formalin 

 to albuminous solutions, when coagulation is no longer possible. 

 The albumins in question are then only held in solution if the reac- 

 tion is acid or alkaline ; in a neutral solution they are precipitated. 

 Denaturized and coagulated albumins can only be brought into 

 solution by means which will at the same time produce integral 

 changes in their composition, viz., by means of proteolytic ferments, 

 dilute mineral acids or alkalies, concentrated organic acids under the 

 application of heat, etc. 



The nature of the process which determines denaturization is 

 possibly a primary cleavage. In favor of such a view is the 

 observation that coagulated albumin is more readily hydrolized by 

 ferments. Nothing certain, however, is known. 



Behavior toward Neutral Salts. All albumins and album oses 

 can be precipitated from their solutions by means of certain neutral 



