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EXPERIMENT 24. PROTEIDS IN SOME COMMON FOODS 



(a) Chop the white of a hard boiled egg into bits, put it 

 into a test tube, and add a few drops of nitric acid. Do 

 you observe any effect ? 



Rinse the contents with water and add a few drops of 

 ammonia. What color do the bits assume ? This color is 

 characteristic of all proteids, and is unfailing proof of the 

 presence of proteids. 



Make tests for proteids in meats, onions, beans, or any 

 other foods in which you are particularly interested. 



(b) Mince some lean meat, .pour water over it, and al- 

 low it to stand for a half hour. Draw off the watery liq- 

 uid, and test it for proteids as follows. Fill a tube half 

 full of the liquid, add a pinch of caustic soda, and shake 

 the mixture. Then add a few drops of weak copper sul- 

 phate. If the liquid shows a violet color, proteid matter 

 is present in it. 



Judging from your experiments, would it matter ma- 

 terially whether meat was soaked preparatory to cooking ? 



(c) Put some meat in water and heat it until the meat 

 boils for half an hour. Test the liquids for proteids as be- 

 fore. Does this give you any idea as to the nutritive value 

 of beef tea ? 



