TESTS FOR NUTRIENTS 



55 



bit of hard-boiled white of egg. Pour over it a little strong (80 

 per cent) nitric acid and heat gently. Note the color that 

 appears — a lemon yellow. If a little ammonium hydrate is 



n 



-h 

 Nitric 

 acid 



+ 

 Hesi 



Ammonium 

 liydrate 



\^ 



Colors seen in test for protein. There 

 are two distinct steps in this test. 



A, corn grain before the test; B, when 

 treated with nitric acid ; C, at completion 

 of test, after treatment with ammonium 

 hydrate. 



added (preferably after washing the egg in water), the color changes 

 to a deep orange. This change shows that a protein is present. 



If the protein is in a liquid state, its presence may be proved 

 by heating, for when it coagulates or thickens, as does the white 

 of an egg when boiled, protein in the form of an alhu'min is present. 



Another characteristic protein test easily made at home is 

 burning the substance. If it gives off the odor of burning feath- 

 ers or leather, then protein forms part of its composition. 



A test of the cotyledon of a bean with nitric acid and ammonium 

 hydrate shows us the presence of protein. Beans are found by 

 many tests to contain about 23 per cent of protein, 59 per cent 

 of carbohydrates, and 2 per cent of oils. The young plant within 

 a bean is thus shown to be well supplied with nourishment until 

 it is able to take care of itself. In this respect it is somewhat like 

 a young animal within the egg, — a bird or fish, for example. 



Germination of the Bean. — If dry seeds are planted in dry saw- 

 dust or dry earth, they will not grow. A moderate supply of water 

 must be given to them. If seeds are kept in a freezing tempera- 

 ture or at a very high temperature, no growth will take place. 

 A moderate temperature and a moderate water supply are most 

 favorable for their development. 



