DENATURING OF VEGETABLE PROTEINS 43 



to the generally accepted view in regard to the action of alkalies and 

 acids on proteins in general. This subject is greatly in need of further 

 critical study, and with the means at present available more definite in- 

 formation than we now have may be obtained in regard to the changes 

 which the protein undergoes. 



C. Denaturing by Alcohol. 



Alcohol produces a marked denaturing effect on many of the animal 

 proteins, and the ease with which such changes are effected is different 

 with the different proteins. Thus ovalbumin is quickly converted into 

 a product insoluble in water, but serumalbumin resists this change for 

 a longer time. Many of the proteins of seeds appear to be but little 

 affected by a long treatment with alcohol, and the evidence that any 

 change whatever is caused by alcohol is of such an uncertain character 

 that definite statements in regard to the action of alcohol cannot at 

 present be made. Zein shows an apparently unique behaviour toward 

 alcohol, for when dissolved in strong alcohol the original solution 

 gradually becomes gelatinous and finally is converted into a firm jelly 

 which is a combination of the zein with alcohol similar to that formed 

 by gelatin with water when its hot solutions are cooled. The formation 

 of this combination depends on the concentration of the solution in 

 zein and apparently also on other conditions, the nature of which is 

 not yet known. Whether an actual denaturing of the protein here 

 occurs is uncertain, but this appears to be the case, for it has not yet 

 been found possible, by any of the numerous means that have been 

 employed, to restore the zein to its original solubility in alcohol after 

 this change has once taken place. Such a change has not yet been 

 observed with any of the other alcohol-soluble proteins. 



D. Denaturing by Metallic Salts. 



It is generally recognised that the addition of salts of the heavy 

 metals to solutions of a protein result in the denaturing of the protein. 

 It is probable, from experiments which have been made with edestin, 

 that this denaturing is largely if not wholly due to the fact that such 

 metallic salts are hydrolytically dissociated with a strong acid reaction 

 and that, in the presence of the acid thus set free, the protein is rapidly 

 denatured. Solutions of ferric chloride behave toward edestin in al- 

 most exactly the same manner as pure hydrochloric acid, the edestin 

 being denatured with the formation of a product soluble in dilute acid 

 but not precipitated by an excess of ferric chloride. It is probable 

 that the acid set free by hydrolytic dissociation of the metallic salts is 



