ANALYSIS OF PERMITTED COLORS, 1907. 181 



7. Thus Weyl, speaking of his Metanitrazotin (p. 120), describes 

 the purification method as follows: 



It is dissolved in warm alcoholic solution of sodium hydroxid filtered and precipi- 

 tated with hydrochloric acid. The precipitate is freed from the adhering liquid by 

 the aspirator and washed with hot water. 



8. Weyl says of his Metanil Yellow (p. 130) : 



For purification the color was dissolved in water filtered and separated by the 

 addition of sodium acetate. The yellow mass was freed from the adherent liquid by 

 the filter pump and dissolved in hot alcohol, in which.it is difficultly soluble, and 

 obtained from this in the form of yellow crystals. The material used for the experi- 

 ment was almost pure, as the following analytical statement shows: 0.4895 gram of 

 the color dried in 105 gave 0.084 sodium sulphate. Sodium required, 6.1; found, 5.6. 

 (Note. This amounts to 91.8 per cent of theory.) 



9. Weyl (Zts. Hygiene, 1889, Vol. II, p. 84, On Safranin 

 Poisoning) describes the difficulties he had in obtaining safranin on 

 the market that was clean or pure; all preparations were free from 

 arsenic, and contained small amounts of iron, chlorin, and traces 

 of chromium. In one specimen the ash amounted to 4.8 per cent. 

 The theoretical percentage of nitrogen in pure safranin is, according 

 to Weyl, 15.3 per cent; in two commercial products he found 12.7 

 and 12.3 per cent, respectively (83 and 80.4 per cent of theory); 

 he recrystallized the specimen containing 12.7 per cent twice from 

 dilute hydrochloric acid; the first recrystallization produced a speci- 

 men containing 13.8 per cent (90.2 per cent of theory) of nitrogen; 

 the second recrystallization produced a substance containing 14 

 per cent (91.5 per cent of theory) nitrogen. 



10. Chlopin in his book (p. 110) says: 



Nevertheless, each dye was tested by me personally with the usual reagents and 

 the dyeing of fabric in order to avoid the confounding of one dye with another. I 

 convinced myself, from my experience, that not only druggists but the home offices 

 of the makers occasionally send dyes which do not correspond to the requirements 

 and resemble them only in name. 



(Page 114.) All the dyes, which according to my experiments proved to be pois- 

 onous, were carefully examined for contents of arsenic, chromium, and injurious 

 metals, and were found to be free from these admixtures. 



FIRST METHODS OF ANALYSIS USED. 



In the summer of 1907 there were on the United States market 30 

 different specimens of the seven permitted colors of Food Inspection 

 Decision No. 76. A chemical examination of those 30 specimens 

 would disclose the qualitative conditions of the market so far as 

 these seven permitted colors were concerned, and it was expected 

 that certain limits for standards of cleanliness would be fixed by 

 such an examination. 



