162 GENERAL BIOLOGY 



with the substance to be tested and allowed to remain for 

 a few minutes, then filtered and the filtrate evaporated in 

 a draft. The oil, if present, will be left behind in the dish. 

 Protein. Place the substance to be tested in a test tube, 

 add a few drops of strong nitric acid and boil. Cool and 

 carefully add a few drops of ammonia. A yellow color 

 appearing when the nitric acid is boiled and becoming a 

 deep orange on the addition of the ammonia is an indication 

 of the presence of the protein. This is one of the best and 

 most easily made tests for protein. 



