AGRICULTURAL CHEMISTRY 



solve in 10 cc. cold water, add 2 cc. alkaline copper sulfate solution, 

 and heat cautiously for about a minute. Cane-sugar, unless in- 

 verted, gives no reaction with copper sulfate solution. Compare 

 this result with the first test. Observe that in the first test the same 

 precipitate is obtained as in Experiment 34. 



Questions, (i) What is meant by inversion of cane-sugar? (2) 

 Why was hot sulf uric acid used? Write the reaction. (3) Why 

 was CaCO 3 used? (4) What becomes of the calcium salt when the 

 solution is filtered ? (5) What was the result when the filtrate was 

 heated with alkaline copper sulfate solution (Fehling's solution)? 

 (6) Did the sucrose, when tested, give any reaction with this 

 reagent? (7) Under what condition in nature does this process of 

 inversion take place? (8) What are invert sugars? 



248. Refining of Sugar. At the present time, the 

 larger portion of commercial sugar is obtained from sugar- 

 beets. In the diffusion process of manufacture, the beets, 

 after cleaning and slicing, are passed into large tanks, 

 where they are subjected to water under pressure which 

 removes the sugar by liquid diffusion. The impurities 

 associated with the sucrose are precipitated with lime 

 water, Ca(OH) 2 , the excess of lime being removed by 

 carbon dioxid gas which converts the calcium hydroxid 

 into insoluble calcium carbonate. For the purpose of pro- 

 ducing the pure lime and the carbon dioxid gas, lime- 

 stone is burned in specially constructed kilns at the sugar 

 factory. After the removal of the impurities and 

 lime, the solution containing the sugar is concentrated in 

 a large vacuum pan and allowed to crystallize ; the crys- 

 tals are then washed in centrifugal washing machines 

 and granulated. Commercial sugar is ordinarily about 

 99 per cent, pure sucrose. 



249. Occurrence of Dextrose. Dextrose occurs widely 



