192 AGRICULTURAL CHEMISTRY 



Tests for glucose. Place about 3 cc. of glucose solution in a test- 

 tube, add 3 cc. alkaline solution of copper sulfate, called Fehling's 

 solution (see Experiment 34), and heat. Then take about o.i gram 

 of glucose from the shelf bottle, dissolve it in 5 cc. water, add 3 cc. 

 Fehling's solution. Heat, and compare with the first test. 



Questions. ( i ) Why was sulf uric acid used in this experiment ? 

 (2) What chemical change did the starch undergo? Write the 

 reaction. (3) Why was CaCO 3 used? Write the reaction. (4) 

 Was any reaction obtained with iodin for starch? (5) What was 

 the result when the glucose solution was added to the hot alkaline 

 solution of copper sulf ate ? (6) How did this precipitate compare 

 with that obtained when glucose from the shelf bottle was used ? 



251. Levulose, commonly called fruit-sugar, is formed 

 along with dextrose whenever sucrose undergoes inver- 

 sion. It has the same formula as dextrose, C 6 H 12 O 6 , but 

 different chemical and physical properties, due to a differ- 

 ent structural composition. Levulose is very sweet, and 

 is found in many ripe fruits and vegetables. Its proper- 

 ties are somewhat similar to those of dextrose, but it is 

 more susceptible to the action of heat, acids, and alkalies, 

 and less to the action of ferments. 



Experiment 50. Levulose and reducing sugars from carrots. 

 Reduce a small clean carrot to a pulp. Place the pulp in a beaker 

 and add 200 cc. water. After half an hour, filter, heat the filtrate 

 for fifteen minutes and then filter a second time. Evaporate 50 cc. 

 of the filtrate nearly to dryness. Test a portion with Fehling's 

 solution as in Experiment 49. 



Questions, (i) How was sugar separated from the carrots? 

 (2) What was the result when the filtrate was heated, and what 

 compounds were precipitated ? (3) Describe the appearance of the 

 concentrated filtrate. (4) What reaction was obtained with 

 Fehling's solution? (5) How does levulose differ in composition 

 and properties from dextrose ? 



