192 COAL-TAR COLORS USED IN FOOD PRODUCTS. 



XV. GUIDES IN DETERMINING DEGREE OF PURITY AND 



CLEANLINESS. 



In view of the absence of any statements in the literature denning 

 the purity of the colors physiologically examined with such accuracy 

 that another could obtain with reasonable certainty the same degree 

 of cleanliness, it became necessary to devise some guide, no matter 

 how empirical, in the setting up of standards, tentative or otherwise. 



As a first consideration it was held that, in view of the fact that all 

 of the physiological work had been done with specimens of coal-tar 

 colors of commercial purity, it would be reasonable to suppose that 

 coal-tar colors produced in the purest form possible with present-day 

 methods would certainly be as clean and as free from admixture as 

 any of the commercial products subjected to physiological test. It 

 was considered unreasonable to expect that increasing the degree of 

 purity of these substances could in any way increase any harmful 

 property possessed by them. Certainly in the case of Naphthol 

 Yellows, where Martius Yellow is a usual contaminant, it can hardly 

 be maintained that decreasing the amount of Martius Yellow would 

 increase any harmful property which might reside in Naphthol Yel- 

 low S proper; in the case of Ponceau 3 R it could hardly be argued 

 that any undisazotized base or decomposition products of diazo 

 compounds tended to correct or counteract any harmful property 

 that might reside in Ponceau 3 R proper; nor could it be maintained 

 that Orange I free from uncombined alpha-naphthol was more harmful 

 than Orange I, contaminated with alpha-naphthol, and so on through 

 the list of the seven permitted colors. This point would not be 

 raised had it not been pressed repeatedly by different persons as a 

 serious objection to quality control and purity standards of the seven 

 permitted colors of Food Inspection Decision No. 76. 



With this rule in mind, and referring to the tabulated results of the 

 analyses of the 30 specimens of the seven permitted colors just given, 

 the items in the analytical statements will each be separately 

 discussed. 



Common salt and ether extractive. Common salt is a legitimate com- 

 ponent of commercial brands of coal-tar colors in so far as these 

 oal-tar colors are obtained by the so-called "salting out" process. 

 The coal-tar colors are recovered from solution by the addition of 

 common salt, which has the peculiar property of separating the coal- 

 tar color from the water solution as an undissolved solid. The 

 coal-tar color so obtained will contain more or less salt, which, from a 

 commercial manufacturing point of view, is therefore an unavoidable 

 constituent. The amount of salt so accompanying the coal-tar 

 color depends upon the amount added to the color solution, and this 

 is greatest when complete exhaustion of the coal-tar color solution 

 is attempted. It is a matter of common experience that, as a rule, 



