PROBLEM 30 59 



Method. — Place material to be tested in a test tube, with a 

 little strong nitric acid, and heat gently. Note any color that 

 appears. Rinse with water to wash off acid. Add a little am- 

 monia and note any change in color. 



Observations. — What change in color takes place when the 

 material is heated with nitric acid? 



Note. — if a lemon-yellow color appears after the addition of nitric acid fol- 

 lowed by a deep orange color on addition of ammonia, there is protein present. 



Home Experiments. Method 1. — Put some white of egg in a 

 saucepan and heat it. 



Observations. — What happens as the white of egg is heated? 



Note. — Any substance thickening and becoming white in color is said to 

 coagulate, and this indicates the presence of an albumen (a protein). 



Method 2. — Burn a hair, a feather, or a piece of meat. 



Observations. — Note the peculiar odor of burning hair or 

 feather. This shows the presence of a protein. 



Conclusion. — 1. What are three ways of knowing the presence 

 of proteins in a given substance? 



2. By means of the nitric acid and ammonia test, find out 

 whether there is protein present in the cotyledons of beans. 

 Write up in experimental form. 



Tests for Inorganic Nutrients 



Problem 30: To test for the presence of mineral matter. 

 (Optional.) 



Materials. — Meat, tin plate, and flame. 



Method. — Heat a piece of meat in a tin plate over a very hot 

 fire. 



Observations. — Does all the meat disappear? Describe what 

 is left. 



NOTE. — The remainder is a tasteless or slightly salty mass of mineral matter. 



Conclusion. — How can you determine whether a substance 

 contains mineral matter? 



Home Work. — Test beans to see whether there is any mineral 

 matter present, remembering that when heated to a sufficient tern- 



