20 



B. SEPARATION AND IDENTIFICATION OF THE COAL-TAR COLORS. 

 a. METHOD OF SOSTEGNI AND CARPENTIERI. 



Zts. anal. Chem., 1896, 35, 397; U. S. Dept. Agr., Div. of Chem., Bui. 46, Rev., p. 

 68; Bui 65, p. Ill (Tolnian). 



6. ARATA'S METHOD. 



Zts. anal. Chem., 1889, 28, 639; U. S. Dept. Agr., Div. of Chem., Bui. 65, p. 112 

 (Tolman). 



It must be observed that certain natural coloring matters dye wool in the eeeond 

 bath, i. e., orchil, cudbear, etc. See Tolman, J. Amer. Chem. Soc., 1905, 67, 25. 



C. WoLFF-WlNTERTHUR METHOD. 



This is an application of the method of Cazeneuve (already described) 

 for the separation of the coloring matters into groups. Proceed as 

 follows: 



Ten cc of wine are shaken with a cold saturated solution of mercuric chlorid, and 

 after the addition of 10 drops of potassium hydrate (sp. gr. 1.27) and again shaking,, 

 is passed through a dry filter paper. 



(1^) Faint yellow filtrate: Add acetic acid to acid reaction; the filtrate becomes 

 rose colored. Acid fuchsin. 



(2) Filtrate; yellow red, rose, red-violet. Acidify with hydrochloric acid; (o) the 

 color remains unchanged or only rose colored: Oxyazo colors, as Bordeaux, pon- 

 ceau, etc.; (6) the color changes from yellow-red to blue-red or blue-violet: Amido- 

 azo colors, as Congo, benzopurpurin, methyl orange, etc. Excess of alkali brings 

 back the original colors. 



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

 Paris municipal laboratory method. 



Girard and Dupre, Anal, de matieres, etc., p. 167; U. S. Dept. Agr., Div. of Chem., 

 Bui. 65, p. 113 (Tolman). 



As the solubility of the numerous coal-tar colors in amyl alcohol from alkaline and 

 acid solution has not as yet been satisfactorily tabulated, complete reliance can not 

 be placed on the use of amyl alcohol as the sole solvent for all dyes; hence the writer 

 suggests the successive extraction of the solution both in acid and alkaline condition 

 with such solvents as ether, acetic ether, acetone, and benzol, in addition to the amyl 

 alcohol, combining the alkaline extracts and the acid extracts, and evaporating 

 each of the combined extracts separately to dry ness, after washing and filtering, in 

 the presence of a piece of wool. The basic and acid colors will then be dyed on 

 separate pieces of wool and can be further examined. In either of the above methods 

 the dyed wool should be further examined for the identity of the coal-tar color or 

 colors. This may be done directly on the dyed fiber a to a certain extent, or by dis- 

 solving out the dye and applying reagents to the extracted dye. 



To remove the color wash the wool with dilute tartaric acid and then with water 

 and dry between filter paper. Saturate the wool with strong sulphuric acid and 

 press out the color with a glass rod after from five to ten minutes and dilute with 

 10 cc of water. Remove the wool, make solution alkaline with ammonia, and when 

 cold extract with 5 to 10 cc of amyl alcohol or other suitable solvent. Separate the 



Lehne and Rusterholze, J. Soc. Chem. Ind., U, 72; Analyst, 1899, 24, 41. 



