68 PHYSIOLOGY FOR THE LABORATORY. 



B. Carbohydrates in Foods Starch. 



I. THE IODINE TEST FOR STARCH. 



Materials. A few grains of starch. An aqueous or alcoholic 

 solution of iodine. Water. 



Apparatus. A test-tube. Bunsen burner. 



Experiment : 



1. Thoroughly mix the starch with about lOc.c. of 



cold water. 



2. Dilute, boil, and cool. 



3. Add a few c.c. of iodine solution. 



4. Dilute again if the color is very dark. Boil 



and cool. 



II. STARCH IN POTATO. 



Materials. Potato. Water. Iodine solution (either aqueous or 

 alcoholic). 



Apparatus. Evaporating dish. Knife. Bunsen burner. 



Experiment : 



1. Wash thoroughly a potato and peel it. 



2. Grate or slice it very thin and wash in an 



evaporating dish. 



3. Collect the white sediment. 



4. Boil some of this with water. 



5. Test for starch with iodine. 



III. THE STRUCTURE OF THE STARCH GRAINS OF THE 



POTATO. 



Materials. A few starch grains just washed from a potato. 

 Apparatus. Glass slide. Cover-glass. Compound microscope. 



