. A civic biology : presented in problems. Biology; Sanitation. 68 PLANT GROWTH AND NUTRITION. A Test for Grape Sugar. - - Place in a test tube the substance to be tested and heat it in a little water so as to dissolve the sugar. Add to the fluid twice its bulk of Fehling's solution,1 which has been previously prepared. Heat the mix- ture, which should now have a blue color, in the test tube. If grape sugar is present in considerable quantity, the contents of the tube will turn first a greenish, then yellow, and finally a brick-red color. Smaller amounts will show less decided red. No other su
. A civic biology : presented in problems. Biology; Sanitation. 68 PLANT GROWTH AND NUTRITION. A Test for Grape Sugar. - - Place in a test tube the substance to be tested and heat it in a little water so as to dissolve the sugar. Add to the fluid twice its bulk of Fehling's solution,1 which has been previously prepared. Heat the mix- ture, which should now have a blue color, in the test tube. If grape sugar is present in considerable quantity, the contents of the tube will turn first a greenish, then yellow, and finally a brick-red color. Smaller amounts will show less decided red. No other sub- stance than sugar will give this reac- tion. If Benedict's test1 is used, a colored precipitate will appear in the test tube after boiling. Starch changed to Grape Sugar in the Corn. - That starch is being changed to grape sugar in the germi- nating corn grain can easily be shown if we cut lengthwise through the embryos of half a dozen grains of corn that have just begun to germinate, place them in a test tube with some Fehling's solu- tion, and heat almost to the boiling point. They will be found to give a reaction showing the presence of sugar along the edge of the cotyledon and between it and the endosperm. Digestion. - This change of starch to grape sugar in the corn is a process of digestion. If you chew a bit of unsweetened cracker in the mouth for a little time, it will begin to taste sweet, and if the chewed cracker, which we know contains starch, is tested with Fehling's solution, some of the starch will be found to have changed to grape sugar. Here, again, a process of digestion has taken place. In both the corn and in the mouth, the change is brought about by the action of peculiar substances known as digestive ferments, or enzymes. Such substances have the power under certain conditions to change insoluble foods - - solids - - into Test for grape sugar. 1 Directions for making these solutions will be found in Hunter's Laboratory Problems in Civic Please
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