FOOD ANALYSIS 267 



evaporate in a clean dish; the oil which remains came from 

 the material tested. In this way test other substances. 



/. Place the material to be tested in a test tube, and pour 

 over it concentrated nitric acid. A yellow color indicates a 

 proteid. Wash the substance and add a little ammonium 

 hydrate. A dark orange is a sure test for a proteid. Another 

 test is to burn a little of the material. The odor of burning 

 feathers indicates the presence of a proteid. 



Experiment 87. Food Preservatives and Colors. 



Apparatus : Ring stand, burner, asbestos mat, evaporating 

 dish, funnel, pipette. 



Materials : Concentrated sulphuric acid, ether, gasoline, 

 ferric chloride solution, 1 per cent, formaldehyde test solution 

 (add 1 c.c. of 10 per cent ferric chloride solution to 1000 c.c. 

 concentrated hydrochloric acid), barium chloride solution, 

 10 per cent, chloroform, bromine water, filter paper, turmeric 

 paper, litmus paper, baking soda, concentrated nitric acid, 

 concentrated hydrochloric acid, ammonium hydrate. 



a. Test for copper: Place substance in evaporating dish 

 and burn it with strong sulphuric acid and heat. Add nitric 

 acid, a little at a time, until all carbon is removed. Add a 

 little hydrochloric acid to ash, filter, and add ammonium hy- 

 drate. A blue color indicates copper. 



b. Test for anatto : Make the sample of milk slightly al- 

 kaline with baking soda, and let a piece of filter paper remain 

 in it for a day. If the paper is stained a reddish yellow, there 

 is anatto present. Anatto is harmless, but it is put into milk 

 with intention to deceive. 



c. Test for formaldehyde: Add formaldehyde test solution 

 to the material, and warm nearly to boiling. A violet color 

 indicates formaldehyde. 



