42 MANUAL OF GENERAL AGRICULTURE. 



insert one end into the stopper and the other end into the 

 lime water, arranging the apparatus on a ring-stand. 

 Gently heat the starch in the test tube. The milky ap- 

 pearance of the lime-water indicates the presence of 

 carbon dioxid in starch. Test the breath for carbon 

 dioxid gas by blowing through a tube into a test tube 

 one-third full of clear lime water. 



Questions: 1. What two compounds does starch 

 contain ? 2. What three elements does starch contain ? 3. 

 To what class of plant compounds does starch belong, or- 

 ganic or inorganic ? 



39. INVERSION OF CANE SUGAR (SUCROSE). 



Materials: Cane sugar, evaporating dish, sulphuric 

 acid, sand bath, Fehling's solution, calcium carbonate, fil- 

 ter paper, funnel. 



There is no direct simple test for cane sugar but by 

 changing the cane sugar to grape sugar we get an indirect 

 test. This change is known as inversion of cane sugar. 



Place 2 grams of sugar in an evaporating dish and 

 add 30 c.c. of water and 2 c.c. of sulphuric acid. Heat 

 fifteen minutes on a sand bath, replacing the water lost 

 by evaporation. Neutralize with calcium carbonate. De- 

 termine when neutral by using litmus paper. Add more 

 water for filtration if necessary. Test with Fehling's 

 solution. Result ? 



Take one-tenth gram of cane sugar, dissolve in 10 c.c. 

 of cold water and test with Fehling's solution. Result? 



Question: 1. What is the object of adding calcium 

 carbonate ? 



40. PREPARATION OF GLUCOSE (GRAPE SUGAR.) 



Materials: Evaporating dish, sand bath, starch, cal- 

 cium carbonate, litmus paper, iodin solution, filter, stir- 

 ring rod, Fehling's solution. 



Add 10 drops of sulphuric acid to about 35 c.c. of wa- 

 ter in an evaporating dish. Heat on a sand bath until the 

 boiling point is reached. Add 1 gram of pulverized starch, 

 noting its appearance immediately after adding. Heat 25 



