COLORING MATTKK. 



118 



Biebrich scarlet gives a green; Bordeaux red and crocein scarlet give blue; tropae- 

 olin OO< ) and solid red give violet. 



If the wool is well dyed most of these colors may be obtained on the fabric. 



This gives only the reactions of a few of the more common colors. In order to 

 carry the work farther the more complete works referred to will have to be used. 



4. DETECTION OF COAL-TAR COLORS BY EXTRACTION WITH SOLVENTS. 



In the Paris Municipal Laboratory* the following scheme of extraction of coal-tar 

 colors is used: 



The acid colors, sulphu-fuchsin, azo derivatives, and phthaleins are not precipitated 

 by tannin and are insoluble or only slightly soluble in acetic ether or arnyl alcohol. 



The basic colors (fuchsin, safranin, etc.) are precipitated by tannin and readily 

 soluble in acetic ether or amyl alcohol. 



I. To 50 cc of wine add ammonium hydroxid in slight excess; then add 15 cc of 

 amyl alcohol, shake, and allow to stand. 



1. If the alcohol be colored red or violet, decant, wash, filter, evaporate to dryness 

 in presence of a piece of wool, and test the dyed wool with sulphuric acid. 



2. If the alcohol be not colored, separate, and add acetic acid. If the alcohol 

 becomes colored the presence of basic aniline color is indicated. 



3. If the amyl alcohol is uncolored, both before and after the addition of acetic 

 acid, no basic coal-tar color is present. 



II. Add an excess of calcined magnesia and then a 20 per cent solution of mercuric 

 acetate and bring to a boil. A coloration before or after addition of acetic acid indi- 

 cates the presence of coal-tar dyes, particularly acid dyes. 



III. Extract the solution with acetic ether made alkaline by barium hydroxid. 

 Tli is dissolves basic colors. 



In any case the colors must be fixed on wool, as many of the fruit colors are 

 extracted and will give reactions with sulphuric acid, which may be mistaken for 

 coal-tar colors. 



The extraction of fruit colors is shown in the following tables, the first of which 

 was prepared by Truchon and Martin-Claude, b and the second by the writer. The 

 fresh fruit juice was very slightly acidified by hydrochloric acid before extraction. 

 In no case in the dyeing test was there any danger of mistaking the vegetable color 

 for one of coal-tar origin where the double-dyeing method was used. 



Extraction of fruit colors with amyl-alcohol. 



MJirard and Dupre Analyse des Matieres, etc., p. 167 

 '.loiirn. phann. chim., 1901, 13, 174. 

 "Acidity of the juice. 



16648 No. 6502 8 



