EXERCISE 35 



The grease-spot test is used to determine the presence of oil or fat. If you rub your fingers through 

 your hair and press them to a sheet of paper, a translucent spot will appear. There are oil glands in the 

 scalp which give off droplets of the material that registers on the paper. 



Problem. What common grains or seeds contain oil ? 



What to use. Clean white paper ; various kinds of grains and seeds (for example, corn, bean, pea, 

 oats, peanut, barley, flaxseed, squash, cottonseed, rye, radish, castor bean) ; small mortar or other means 

 of crushing seeds. 



What to do. Crush or grind the seeds or grains separately. Place a quantity of the meal on white 

 paper, writing name of seed used alongside. Arrange all the heaps of meal in order, and place the 

 paper in a mild oven or other warm place, allowing the fat which may be present to melt down and flow 

 into the paper. 



Results will appear after the meal has been brushed away. 



Record. Make a list of the materials tested and indicate opposite each whether fat (oil) is present 

 or absent. 



Questions. 1. What seeds contain large quantities of oil ? 



2. Which of the seeds tested contain both oil (fat) and starch ? 



3. How is fat rendered from beef or pork ? 



4. How does a grease spot on paper differ from a water spot? 



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