300 



A YEAR IN SCIENCE 



and iron. These elements form complex compounds, the 

 exact composition of which is not known. 



Water 73,7 



Fat 4.0 



Protein 

 2.2 



FatOl 

 Carbo- 

 hydrate 18.4 POTATO 



Water 2.5 

 Protein 16.6 



Fat 63.4 



Ash 1.4 



WALNUT 



Permission U. S. Dejjt. of Agriculture. 

 Fig. 146. Showing the foodstuffs in different foods. 



Test of protein. There are a number of ways in 

 which the presence of protein in food may be detected. 

 One of the best methods is the use of nitric acid and 

 ammonia. Some of the food to be tested is placed in a 



