MATERIALS PRESENT IN PLANTS 95 



b. Nitrogen. Thoroughly mix about a test tube full of fine 

 grass cuttings with half a test tube full of slaked lime. Soda- 

 lime is still better; use it if you can. Put the mixture into 

 your iron dish. Cover the dish with a clean piece of glass on 

 the under side of which you have pasted a piece of wet, red 

 litmus paper. Heat the dish carefully; does the litmus change 

 color? If so, ammonia is being given off. Can you get its 

 odor? If ammonia is given off, the grass must contain nitrogen 

 (cf. 112, text). 



Try the same test with flour instead of with grass. Use 

 equal volumes of flour and lime (or soda-lime). What are the 

 results? Does flour contain nitrogen? 



c. Starch. Cook a pinch of laundry starch with half a 

 test tube full of water. Pour the liquid out into a white saucer 

 or evaporating dish to cool; then add a drop of iodine solution 

 (a small crystal of iodine dissolved in 5 cu. cm. of a dilute 

 solution of potassium iodide). What happens? This is a test 

 for starch. 



Try the experiment with a pinch of flour instead of starch. 

 Try it again with corn meal; also with scrapings from the freshly 

 cut surface of a potato. Try it with the scrapings from a 

 radish, parsnip, or sweet potato. Give all the results. 



d. Fat. Put a speck of lard or linseed oil on a piece of clean, 

 white writing paper; then wipe off the lard or oil, and hold the 

 paper between you and the light. What do you see? 



Put a drop of benzine on the paper, and hold the paper to 

 the light. Does benzine produce a permanent stain on the 

 paper? 



Put a small heap of corn meal on the paper and wet the meal 

 with benzine. After 3 or 4 minutes remove the meal, and let 

 the benzine evaporate. Is there a stain? Do the same with 

 ground flax seed. Result? Is fat present in the seeds of corn 

 and of flax? 



