TO TEST FOODS FOR NITROGENOUS SUBSTANCES. 25 



grape-sugar; and into a third test-tube 

 some mutton tallow (fat). Add a little 

 concentrated nitric acid to each of the 

 three. 



a. Do you observe any change in the 



color of either of these nutrients? 



b. Pour off the acid and add a little con- 



centrated ammonia. Is any effect 

 noticeable ? 



3. Test with a drop of nitric acid the skin on 



the tip of one of your fingers. 



a. What is the result? 



b. Of what material is the human body 



partly composed ? 



4. Apply the nitric acid and ammonia test to 



as many foods as you can (e.g., gelatin, 

 peas, white meats, onions, fruits). 



5. Tabulate your results in columns under the 



following heads : 



D. From the above experiments state briefly three 

 .ways of testing foods for nitrogenous sub- 

 stances. 



