180 COAL-TAR COLORS USED IN FOOD PRODUCTS. 



with another substance. My own investigations were made on dogs with a preparation 

 for which I am indebted to the kindness of Dr. G. Schultz, of the Aniline Manufactur- 

 ing Co. of Berlin. It was purified by precipitation and recrystallization. 



2. Fraenkel (p. 578) expresses the opinion that the harmful results 

 observed with Metanil Yellow (95 of the Green Tables) may be due to 

 diphenylamin contained in the color, which diphenylamin may be 

 a decomposition product of the Metanil Yellow, particularly since, as 

 Weyl states (p. ISO), it "smelled strongly of diphenylamin. " 



3. Pfeffer ( Unterschungen aus dem Botanischen Institut zu Tuebin- 

 gen, Vol. II, p. 186) says: 



In repeating my experiments I beg that it be considered that differences in observa- 

 tion may be caused by the quality of the coloring matters. For quite apart from the 

 fact that the coloring matters are in part variable mixtures of various compounds, and 

 not infrequently contain foreign admixtures, the quality of the goods brought into 

 market may change from time to time. Thus formerly magenta was the acetate, 

 whereas to-day it is the hydrochlorid. Also foreign admixtures may be poisonous or 

 may exert no influence on the absorption of color. 



4. Stilling (ArcUv. Exper. Path. Pharm.,vol. 28, 1891, p. 352) says: 



With respect to the blue pyoctanin, I have during the entire time been engaged 

 in ascertaining the most effective. The things marketed by E. Merck as P. coeruleum 

 have therefore now become uniform and homogeneous, which could not be the case 

 at the beginning. The P. coeruleum now furnished by E. Merck is the hydrochlorid 

 of pure hexamethylpararosanilin. 



The variable degrees of purity attained by products of this kind 

 on the market was apparently the first cause of the prohibition by 

 the German Government of the coal-tar color known as Corallin for 

 use in food products not because Corallin itself was harmful, but 

 because in the manufacture of this product it was so apt to retain im- 

 purities which in and of themselves produced bad effects, so that this 

 particular color was specifically excluded by the German Government. 



In a few cases it is stated that the substance subjected to physio- 

 logical test had been purified, but these descriptions are hardly such 

 as to enable others to arrive at substantially the same result with 

 reasonable certainty. 



5. Stilling in his monograph entitled Anilin Farbstoffe als Anti- 

 septica (Strassburg, 1890, Pt. I, p. 16) says: 



The foregoing (relative to the action of Methyl Violet on the eyes of rabbits) holds 

 only for pure substances. Many anilin colors of otherwise very antiseptic properties 

 are contaminated with arsenic, particularly the otherwise useful Ethyl Violet. With 

 such substance serious poisonings and death can be produced in experimental animals. 



6. Stilling in Part II of the same monograph, pages 5 and 6, says : 



Such substances (coal-tar colors) must be chemically pure and can not, for example, 

 be any mixture of various blue or violet dyes. There is therefore a great difference 

 whether a substance be tested only bacteriologically or also in addition physiologically 

 and therapeutically. Two preparations may be antiseptically wholly equal, but the 

 one preparation may contain harmful admixtures which produce violent irritations. 



