37 



50 per cent alcohol, the liquid (fat-free) evaporated to a few drops, and some undyed 

 sausage placed in this solution. The muscular fibers and the fat cells are then stained 

 deeply. The sausages should also be extracted with ammonia water, which is a bet- 

 ter solvent than alcohol for many of the colors used in flesh dyes. Marpmann 

 regards with suspicion all sausages which remain colored after being kept for two 

 hours in 50 per cent alcohol, since normal flesh is decolorized under these conditions. 

 The following table shows the behavior of different flesh proteids on treatment with 

 certain anilin colors: 



Behavior of flesh proteids treated with anilin colors. 



VIII. Coffee, Tea, Cocoa, Spices, etc. 

 COLORING MATTERS CONSIDERED. 



Turmeric, caramel, chicory, roasted cereals, azo dyes, indigo, catechu, campechy 

 wood, humus, kino, graphite, mineral pigments. 



FACINGS. 



Unroasted coffee beans contain viridic acid, which is soluble in sulphuric acid 

 with a crimson color turning bright green on addition of alkalis. Inferior or dam- 

 aged coffees are not infrequently treated by some process for improving their appear- 

 ance and giving them the appearance of superior grades. For this purpose mineral 

 pigments may be used for facing or coloring and azo dyes for brightening. The natu- 

 ral coloring matter of tea is extracted from the dry leaves by hot alcohol, giving a 

 yellowish-green solution, turning bright yellow on adding ammonia. Sulphuric acid 

 (cone.) on the color gives a bright green, remaining green on addition of water. 

 The artificial colorings of tea will be found usually in the form of facings. They 

 may be detected by the microscope by examining a portion of the leaf, when the 

 coloring matter appears as small dots, or by chemical means. 



AZO DYES. 



Treat with hot strong alcohol, evaporate to dry ness, take up with warm water and 

 filter, or if necessary separate the fat or oil from the water solution by agitation 

 \vith a suitable solvent. Examine the water solution for coal-tar colors, as under 

 wines. 



INDIGO. 



Under the microscope indigo appears of a greenish blue. Its color is not dis- 

 charged by sodium hydroxid, a distinction from Prussian blue. Indigo forms a deep 

 blue solution with sulphuric acid. Hyposulphite of soda will dissolve indigo, reduc- 

 ing it at the same time. This solution may be used to dip a piec,e of wool in, which 

 on exposure to the air will turn blue if indigo is present. 



U. S. Dept. Agr., Bureau of Chemistry, Bui. 13, Part 7, Tea, coffee, and cocoa 

 preparations, pp. 880, 909. 



