SOPHISTICATION AND SUBSTITUTION 141 



4. Water-treatment for various inorganic color matters: 

 Procedure: — Wash in water; rub with dry towel. 

 Test: — Rubbing will remove cosmetic, if present. 

 Procedure: — Soak beans in cold water. Treat sediment, using 



appropriate qualitative chemical methods for the suspected color- 

 ing-matter (Scheele's green, chrome yellow, Venetian red, etc.). 



5. Alcohol-treatment for organic coloring-matters. 

 Procedure: — Shake beans in alcohol. 



Test: — ^Alcohol is not colored by genuine coffee. 



Procedure: — Evaporate alcoholic solution to dryness. Take up 

 residue in water. 



Test: — Solution will give characteristic reactions of coal-tar 

 dyes if coloring matter is present. 



(a) Indigo Detection: 



Procedure: — Treat sample with dilute nitric acid. Filter; 

 saturate filtrate with sulphuretted hydrogen. Extract Indigo by 

 agitating with chloroform. 



(b) Prussian Blue Detection: 



Procedure: — Prussian Blue and Alkanet root may be separated 

 by warming coffee-sample with a solution of potassium carbonate. 

 Add hydrochloric acid; and Prussian Blue precipitates. Prussian 

 Blue, if present in considerable quantities, may be detected in the 

 sediment, obtained after shaking in water, by the following pro- 

 cedure : — Dissolve the sediment in hot alkali ; filter and acidify 

 with HCl; add drop of ferric chloride. Test: — Precipitation oc- 

 curs if Prussian Blue is present. 



(c) Ultramarine Detection: 



According to Leach, "If the residue on the paper after treat- 

 ment with hot alkali, on removal to a porcelain dish and treatment 

 with concentrated H2SO4, yields hydrogen sulphide (recognize 

 by odor or by the blackening of lead acetate paper), ultramarine is 

 present." 



B. Roasted Bean Tests: 



I. Density-test for factitious beans: 



Procedure: — Place a small handful of beans on surface of full 

 beaker of water. 



