ORGANIC COMPOUNDS OF PLANTS IQI 



distributed in nature. It is found in small amounts in 

 the sap of saccharine plants, in seeds, ripe fruit, honey, 

 animal tissues, and all food products in which the 

 sucrose has undergone inversion. 



250. Chemical and Physical Properties. Dextrose is a 

 solid, white substance which gives off water from its mole- 

 cule when heated to 170 C. At 200 C. , volatile gases 

 and acid products are formed. Acids and alkalies act 

 upon dextrose and produce a large number of compounds. 

 Dextrose is capable of undergoing a number of different 

 kinds of fermentation, alcohol, succinic acid, lactic acid, 

 and glycerol being some of the products formed. When- 

 ever foods which contain dextrose are exposed to favor- 

 able conditions, fermentation takes place. Dextrose is 

 produced commercially by the action of dilute acids upon 

 starch. The acid causes a molecule of water to unite 

 chemically with a molecule of starch. 



C 8 H 10 5 + H 2 = C 6 H I2 S . 



The thick syrup that is formed after the acid is neu- 

 tralized is called glucose syrup. If a solid mass is pro- 

 duced, it is called grape-sugar. 



Experiment 49. Preparation of glucose. Add 20 drops H 2 SO 4 

 to about 70 cc. water in an evaporator. Heat on the sand-bath 

 until the boiling-point is reached. Then add 2 grams of pulver- 

 ized starch. Observe the appearance of the starch immediately 

 after adding. Heat twenty-five minutes, stirring occasionally, and 

 replacing the water should too much evaporate. Add CaCO 3 to 

 neutralize the H 2 SO 4 ; when neutral to test paper, filter, washing 

 the contents of the filter with 25 cc. of water. Take a few drops of 

 the filtrate and test with iodin for starch. Then evaporate the rest 

 of the filtrate to about 20 cc. and observe its appearance. 



