20 THE CARBOHYDRATES. 



of acetic acid to precipitate the casein (when enough has 

 been added the liquid is nearly clear). Filter. Boil the 

 nitrate and filter off the .coagulated albumin. Evaporate 

 the filtrate upon a water-bath to a syrup and allow it to 

 stand until the sugar has crystallized out. It may be puri- 

 fied by recrystallizing it. 



35. Test the milk-sugar with Trommels, Fehling's, 

 and the phenyl-hydrazin tests, and notice that the results 

 are similar to those obtained with glucose. 



36. Try Barfoed's and the fermentation tests as 

 made with the glucose, and observe that the results are 

 negative. 



37. Boil the milk-sugar solution with a little hydro- 

 chloric acid, neutralize, and try the fermentation or Bar- 

 foed's test. Glucose has been formed and this will now 

 ferment, forming carbon dioxid and alcohol. 



SUCROSE (CANE-SUGAR: C 12 H 22 11 ). 



Cane-sugar is found in plants, not in the animal king- 

 dom. It has no reducing power and does not respond to 

 the tests where such a reducing action occurs,* such as 

 Trommer's, Fehling% and Boettger's. It is decomposed 

 by heating with acid into a molecule of glucose and one 

 of fructose. 



38. Apply Trommer's or Fehling's test to a solution 

 of pure cane-sugar. It gives no results. 



39. Boil a solution of cane-sugar with a little sul- 

 phuric or hydrochloric acid, neutralize the solution, and 

 prove that it contains glucose. 



40. The "invert sugar" which results from the decomposition 

 of cane-sugar by acids can be separated into glucose and fructose 

 by adding to 10 parts 6 parts of calcium hydrate and 50 parts of 

 water. Both sugars form calcium compounds. That with glucose, 





