PLANT PRODUCTS 261 



crush them on a sheet of white writing paper. Hold the 

 paper between you and the light. What does this show ? 

 The grease spot indicates the presence of oil or fat. Test 

 other seeds in this way for oil, such as sunflower, squash 

 or pumpkin, flaxseed, etc. Have some of the pupils put a 

 small pinch of each of the following on a sheet of paper: 

 flour, cornmeal, any cereal breakfast food, buckwheat, and 

 ground coffee. Place the sheet in a hot oven and keep it 

 there several minutes. Now see whether the paper shows 

 that any of these things contain oil. Have the pupils name 

 some plants whose seeds contain so much oil that it is 

 extracted and used for various commercial purposes. 



Besides starch and oil, plants contain other substances 

 known as proteids. In your physiology you may have 

 learned of albumen as a kind of proteid. One of the 

 purest types of proteid known is the white of egg. A 

 chemical test may be made for proteid as follows: Dissolve 

 in a two-ounce bottle of warm water about one fifth of an 

 ounce of caustic potash (potassium hydroxide). Care 

 should be taken not to let the potash touch the hands or 

 clothing. Make another solution by dissolving a piece of 

 copper sulphate (bluestone) about as large as a lima bean 

 in a two-ounce bottle of warm water. Place a small 

 quantity of the white of an egg on a plate or saucer and pour 

 a little of the first solution over it. Warm the plate gently. 

 Be careful not to cook the egg. Now add a little of the 

 second solution and stir with a splinter. What change of 

 color do you note ? The beautiful violet purple is due to 

 the presence of proteid. 



Soak some beans overnight. After removing the skins, 

 crush the beans and place on a warm plate. Test for 



