EXERCISE 81 



Materials. Test tubes ; starch paste ; malted barley or barley grains ; iodine solution and 



Fehling's solution. 



Directions. Partly fill a large test tube or a cup with starch paste made by boiling a half 

 teaspoonful of starch in a half pint of water. 



Prepare a malt extract by securing some dry malted barley and grinding it in a mortar or 

 a coffee grinder; soak 1 or 2 tablespoonfuls of the barley in a cupful of water for an hour; 

 filter off the water, which with the substances in solution is the malt extract. 



If malted barley cannot be had, soak some fresh barley grains in water for from ten to twelve 

 hours, pour off the water, and place the barley in a closely covered dish in a warm place to 

 germinate. When the sprouts are an eighth of an inch long, crush the barley, soak in water, and 

 treat as above. 



To a test tube of starch paste add 1 or 2 cubic centimeters of the malt extract. Allow the 

 mixture to stand for at least half an hour, preferably in a warm place. It may stand overnight with 

 advantage. Test a small sample for starch. Test another sample for grape sugar. 



What change has taken place as to the amount of starch ? of grape sugar ? How do you account 

 for these changes ? 



NOTE. There is always some sugar in the malted barley, and this will be dissolved in the malt extract. 

 Sugar is, therefore, added to the starch paste with the malt extract, but if a small amount of the extract is 

 used, the amount of sugar added will not be great. Some of the pupils may wish to test the malt ex- 

 tract diluted with water instead of starch paste, to determine whether or not all the sugar in. the above 

 test was originally in the malt. They should devise their own method. 



Additional problems. Put some powdered starch in cold water in a test tube, add a small amount of malt 

 extract, and leave in a warm place for twenty-four hours or more. Test with Fehling's solution to see if 

 sugar is present. 



If a microscope is available, examine starch grains which were used in the preceding problem and 

 compare them with starch grains which have not been treated with malt. Do any of the grains show 

 evidence that they have been partly dissolved ? 



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