200 METHODS OF ANALYSIS. 



10. Detection of Cochineal. 



Cochineal is used to a certain extent as a coloring matter in foods, and a 

 very satisfactory test for it is that given in Girard and Dupre> Dissolve the 

 food product in water, filtering if necessary. Acidulate with hydrochloric acid 

 and extract with amyl alcohol, which is colored yellow or orange, the depth 

 of color depending on the quantity of cochineal present. Separate the aniyl 

 alcohol and wash until neutral. Then separate into two portions; to the first 

 add drop by drop a very dilute solution of uranium acetate, shaking thoroughly 

 after each addition. In the presence of cochineal a characteristic emerald-green 

 color is produced. & 



To the second portion add a drop or so of ammonium hydroxid, and in presence 

 of cochineal a violet coloration results. This, however, is not so sensitive to 

 Aery small amounts as the first tests, and many fruit colors give tests hardly 

 to be distinguished. 



Cochineal carmine is liable to contain tin, as it is often a tin lake, although 

 alum is also used. It is also liable to adulteration with lead compounds. 



"Analyse des matieres alimentaires, etc., p. 580. 



* This reaction has been tested on a number of amyl alcohol extracts from fruits, and 

 in no case was there any chance of mistake in the reaction. Most fruits give a brown 

 color, while blackberries and currants give a bluish color. 



