GENERAL CHEMICAL CHARACTERS OF PROTEINS 63 



product when still moist in hot alcohol, and allowing the solution to 

 drop into ether ; a product was thereby obtained which was easily 

 soluble in alcohol, and which could be purified by repeated solution 

 in this solvent and reprecipitation with ether. It contained 10*82 

 per cent, bromine. Derivative III. was prepared by dissolving the 

 moist crude bromination product in alcohol containing bromine, and 

 pouring the solution thus obtained into ether containing bromine. 

 A product resulted which, after washing with ether, contained 14*9 

 per cent, of bromine. 



These derivatives can be converted one into the other. Thus, 

 for example, by dissolving derivative II. in sodium hydroxide solution, 

 and then adding acetic acid, a product containing only about 4 per 

 cent, bromine can be obtained. Conversely, if derivative I. be 

 added to alcohol containing bromine, and the solution thus obtained 

 be thrown into ether containing bromine, a product is obtained 

 which contains about 15 per cent, bromine (derivative III.). 



Derivatives of the third class, containing the largest percentage 

 of bromine, were prepared from several other proteins. The 

 bromine content of the derivatives thus obtained may be regarded 

 as characteristic for each protein. From varying fractions of egg- 

 albumin substances containing from 12*79-16*48 per cent, halogen 

 were obtained ; from serum of different fractions the bromine deriva- 

 tives contained from 12*1 5-12*94 per cent. ; from serum-globulin they 

 contained from I3'53-I4'O3 per cent. The bromine derivative of 

 caseinogen contained 11*17 P er cent, that of proto-albumose 16*30- 

 17*12 per cent., and of deutero-albumose 17*63 per cent. 



It was not found possible to obtain such definite series of 

 derivatives of chlorine or iodine derivatives ; nevertheless, evidence 

 was obtained that such series existed, although substances with definite 

 halogen content were not always obtainable. It was not found possible 

 either to obtain iodine derivatives, corresponding to derivative III. 



Blum and Vaubel also obtained bromine derivatives of proteins, 

 using the method already mentioned, viz., treating with halogen in 

 slightly alkaline solution ; from egg-albumin and caseinogen they 

 obtained products with between 4 and 5 per cent, of bromine. 



Iodine Derivatives of Proteins. 



The earlier investigations on the iodine derivatives are due to 

 Bohm and Berg, and Jendrdssik. 1 The two former noticed the de- 

 colorisation of iodine by protein solutions, and, by coagulation, iso- 

 lated a product from which, by dialysis and washing, the iodine could 

 be removed. Jendrdssik determined the amount of iodine which 

 could be decolourised by a protein solution. Other investigations 

 were published later by Liebrecht and by Lepinois, who obtained 

 products containing respectively 17*8 and 21*6 per cent, iodine, part 

 of which, at any rate, was in stable combination. The chief 

 systematic investigations on the iodine derivatives, apart from the 

 ones on the halogen derivatives generally of Hopkins and Pinkus, 

 and Blum and Vaubel, already mentioned, are those of Hofmeister, 

 Kurajeff and C. H. L. Schmidt. 



Hofmeister worked with crystallised egg-albumin. He treated 

 20 grams dissolved in 400 c.c. water with 10 grams potassium 



1 These earlier investigations are discussed in Hofmeister's paper. 



