GUIDES IN DETERMINING PURITY. 193 



the coal-tar color first separating in the salting-out process is cleaner 

 and less contaminated than the portions last separating. In an 

 endeavor to recover as far as possible all the dissolved coal-tar 

 coloring matter the manufacturer adds a large excess of salt, and 

 this carries with it a large amount of organic matter not coloring 

 matter, as can be seen from the preceding analyses, where a high 

 salt content is almost always accompanied by a high ether extract 

 content. The ether extract content is a measure of the dirt or 

 organic impurities of the coloring matter. 



The objection to an excessive amount of salt in coal-tar coloring 

 matters, when they are to be used for food-coloring purposes, does 

 not reside in the salt per se, but is due to the fact that a high salt 

 content seems generally to be accompanied by an unnecessarily 

 large amount of organic material not coloring matter, and nothing 

 good is known of such material, which is more than likely to be 

 harmful. j 



The acetate ether extract is supposed to represent that part of the 

 organic material not coloring matter which has no, or only slightly, 

 basic properties; the acid ether extract is supposed to represent that 

 part of the organic material not coloring matter which has acid 

 properties. In the case of Naphthol Yellow S the acid ether extract 

 will contain all of the Martius Yellow, and very likely will consist 

 substantially of it. In the case of Erythrosin, of course, no acid ether 

 extraction was attempted because the color acid is itself ether- 

 soluble. 



The following tabulation shows the percentages of salt based on 

 the amount of coloring matter present contained in 26 of the specimens 

 before reported on, arranged under each of the seven permitted 

 colors : 



Naphthol Yellow S: 0.62; 1.04; 2.97; 2.99; 3.51; 3.64; 4.38; 7.38; 11.82; 31.53. 

 (Average, 6.99.) 

 Ponceau 3 R: 27.16. 

 Orange I: 3.91; 11.19. (Average, 7.55.) 



Amaranth: 16.20; 37.39; 39.97; 42.85; 64.37; 68.89. (Average, 44.95.) 

 Light Green SF Yellowish: 0.04; 0.10; 1.64; 1.88. (Average, 0.92.) 

 Indigo Disulpho Acid- 8.31; 8.35; 44.02. (Average, 20.23.) 



The following figures give the same data for the acetate, acid, and 

 total, ether extract: 



Ether extractives. 



ACETATE ETHER EXTRACT. 



Naphthol Yellow S: 0.08; 0.10; 0.13; 0,14; 0.16; 0.16; 0.16; 0.19; 0.27; 0.37. (Aver- 

 age, 0.18.) 



Ponceau 3 R: 0.38. 



Orange I: 0.02; 0.69. (Average, 0.36.) 



Amaranth: 0.03; 0.14; 0.19; 0.31; 0.32; 0.46. (Average, 0.24.; 



97291 Bull. 14712 13 



