Winogradow a ascertained that the following dyes hindered the 

 digestion of albumen by pepsin, even when only a few milligrams 

 of the colors were present (an amount corresponding to from one- 

 tenth to one one-hundredth of the digestive solution), this action being 

 almost inhibitive: 



Safranin. Cceruleine S. Magdala red. 



Ponceau RR. Phloxin RBN. Azoflavin. 



Azofuchsin G. lodoeosin. Benzopurpurin. 



Orange II. Chrysanilin. Cerise. 



The following interfered less than the first-mentioned dyes, but in 

 every case some effect was noticed: 



Acid green. Anilin green. Martius yellow, 



lodin green. Primulin. Metanil yellow. 



Acid azo yellow. Auramin O. Quinolin yellow. 



Yellow T. Anilin orange. Methyl ene green. 

 Naphthol yellow. 



The methods of separating the colors from the material to be exam- 

 ined by the use of solvents involve the separation of the natural colors 

 at the same time, and these must first be isolated before identification 

 tests can be applied. This fact naturally necessitates a very compre- 

 hensive knowledge of the color reactions and the behavior of the 

 natural colors with reagents. Complete data on this subject are as yet 

 wanting. 



The coal-tar dyes may, in general, be most satisfactorily separated 

 by the double-dyeing method, with or without previous extraction 

 with solvents, as the case may be, and in some cases may be identified 

 directly by tests on the dyed fabrics, or more accurately f>y being 

 removed from the fabric and subjected to purification. Great care 

 and judgment must be exercised in applying the color reactions and 

 arriving at a conclusion therefrom, as the presence of more than one 

 dye, or some organic impurity, will lead to erroneous results. Several 

 means of identification should be tried and a conclusion drawn only 

 when the analyst is perfectly satisfied of the identity of the dye. 



Many of the results obtained in the determination of a dye have 

 been rendered ambiguous, owing to confusion of names applied to the 

 same dye, and the analyst should always make a point of identifying 

 any particular dye by giving the name of the original manufacturers, 

 so that its composition may be known; as, for instance, orange Gr 

 might be either of the following in default of a distinguishing mark, 

 viz: 6 



Orange G (C. J.). Anilin azo ft naphthol. 



Orange G (B). Anilin azo 2 naphthol, 6.8 disulphoacid sodium salt. 



Orange G (H.) Sulphanilic acid azo ft naphthol sodium salt. 



Zts. Nahr. Genussm., 1903, 889. 



6 Rawson, Gardner, and Laycock, Dictionary of Dyes, Mordants, etc., 1890; Schultz 

 and Julius, Tables of Dyes. 



