THE PROTEIN SUBSTANCES. 

 VEGETABLE FOODS. 



milky liquid. This is largely starch. After some time an elastic residue 

 is left insoluble in water. This is " gluten " and is the chief nitrogenous 

 element of the flour, which has been already referred to. It may be sepa- 

 rated into several constituents. 



Ex. To about 5 gm. of flour add 10 cc. of water, shake thoroughly and 

 allow to stand until a nearly clear liquid appears above a white sediment. 

 Filter the liquid and test for sugar by the Fehling solution. Boil some 

 of the residue with water and add iodine solution as a test for starch. 



Ex. To about 5 gm. of fine corn meal in a test-tube add 10 cc. of ether. 

 Close the tube with the thumb and shake thoroughly. Then cork and 

 allow to stand half an hour. Shake again and pour the mixture on a 

 small filter, collect the ethereal filtrate in a shallow dish and evaporate it 

 by immersion in warm water. A small amount of fat will remain. 



Action of Yeast on Flour. The following experiment is intended to illus- 

 trate the work done by yeast in leavening dough : 



Ex. Crumble two or three grams of compressed yeast into 15 cc. of 

 lukewarm water and shake or stir the mixture until the yeast is uni- 



