40 



0.01 per cent aqueous solution + stannous chlorid solution=l)right crimson precipitate, 

 purplish by transmitted light. 



0.01 per cent aqueous solution + tannin reagent; test for basic color= precipitate. 



Benedikt's test with zinc and ammonia: (Allen, "Commercial Organic Analysis," 

 vol. 3, part 1, page 322.) 



Conclusion: Pure color, S. & J. 504. 



ROSE BENGAL: 



Qualitative analysis shows halogens, iodin, and chlorin no bromin. 



Benedict's test with zinc dust and ammonia. (See^ Allen, loc. cit.) 



Benedikt's test: Boiling with caustic potash solution. (Sp. gr. 1.3.) (See Allen.) 



Color separated from acidified aqueous solution as in the case of erythrosin. 



Quantitative determination of iodin and chlorin. 



Chlorin determined by silver nitrate after removal of iodin by nitrous acid and 

 carbon bisulphid. 



Iodin determined from total halogens by difference. 



Chlorin, 8.89 per cent; iodin, 49.5 per cent; ratio=l to 5.56. 



Ratio of halogens in tetraiodo-dichlor-fluorescein=l to 7.2. 



Ratio of halogens in tetraiodo-tetrachlor-fluorescein=l to 3.6. 

 iion: Color a mixture of the two Rose Bengals, S. & J. 



520 and 523. 



PHLOXIN: 



Qualitative analysis shows presence of halogens, bromin, and chlorin; no iodin. 



Determination of bromin by Mohr's method gave 39.8 per cent in color, purified by 

 extraction with ether. 



Chlorin, from total halogens by difference =11. 9 per cent. 



Ratio chlorin: bromin=l:3.34. 



Benedikt's test with zinc dust and ammonia. (See Allen.) 



Benedikt's test with boiling potassium hydroxid solution. (See Allen.) 



Conclusion: This color is a mixture of the two phloxins, S. & J. 518 and 521. 

 COCHINEAL RED A, S. & J. 106: 



Tested for mixed color by precipitating part of color from solution with salt, filtering 

 and dyeing wool to same depth with filtrate and solution of precipitated color. Both 

 dyeings were nearly the same shade, indicating fairly pure color. 



Dry color sprinkled on concentrated sulphuric acid shows small amount of foreign 

 color. 



Reduction with stannous chlorid and hydrochloric acid, making alkaline with 

 sodium hydroxid and extracting, gave very little ether-soluble matter. This shows 

 absence of colors yielding ether-soluble bases on reduction. 



Conclusion: Color is fairly pure, but contains a small amount of foreign color. 

 FAST RED C, S. & J. 103: 



Tested for mixed color, as in the case of cochineal red A, by fractional precipitation 

 with salt and by sprinkling on concentrated sulphuric acid. Small amount of foreign 

 color shown. 



Color is fairly pure, but contains a small amount of foreign color. 

 PONCEAU 2R or 3R: 



0.1 per cent aqueous solution + barium chlorid solution (10 per mi)=crimson precipi- 

 tate, insoluble in acetic acid. 



0.1 per cent aqueous solution + calcium chlorid solution (10 per cent) =no precipitate. 



0.1 per cent aqueous solution + lead acetate solution (10 per cen)= crimson precipitate. 



Color reduced with stannous chlorid and hydrochloric acid. Solution made alkaline 

 with caustic soda and distilled with steam. Liquid amido compound distils over, 

 which could not be solidified in ice water. Boiling point about 215 C. This shows 

 the amido compound to be xylidin. 



Conclusion: Color is ponceau 2R or xylidin red, S. & J. 55. 

 ACID GREEN: 



Solubility in absolute and 95 per cent alcohol; no sign of mixed color by sprinkling 

 on wet filter; no chlorin in the ash. 



Conclusion: Pure color, S. &. J. 435. 

 PERSIAN BERRY EXTRACT: 



Reactions correspond very closely to those of a buckthorn berry extract prepared in 

 the laboratory. 



The accompanying table shows the results obtained in the identification of the 

 colors. Considering the fact that three of the collaborators had never undertaken 

 work on the identification of colors before, the results appear to be quite satisfactory 

 with regard to ih< j mal-iar colors. 



