42 PHYSIOLOGICAL CHEMISTRY 



EXPERIMENTS ON SUCROSE 



1-6. Repeat Solubility, Fehling's, Nylander's, Barfoed's, Phenylhydrazine 

 and Fermentation tests according to the directions given under Glucose, pages 

 21-31. 



7. Inversion of Sucrose. To 25 c.c. of sucrose solution in a beaker add 5 

 drops of concentrated H 2 SO4 and boil one minute. Cool the solution and render 

 neutral with saturated barium hydroxide. Filter off the precipitate of baiium 

 sulphate and upon the resulting fluid repeat the phenylhydrazine, Fehling, 

 Nylander's and Barfoed's reactions as given under Glucose, pp. 26, 29 and 30 ; 

 the Resorcinol-Hydrochloric Acid Reaction (Seliwanoff), as given under Fruc- 

 tose, page 35. Explain the results. 



8. Alcoholic Fermentation. Prepare 500 c.c. of a concentrated (10-20 per 

 cent) solution of sucrose, add a small amount of egg albumin or commercial 



peptone and introduce the mixture into a liter flask. 

 Add yeast, and by means of a bent tube connect this 

 flask with a second flask containing a solution of 

 barium hydroxide protected from the air by a soda- 

 lime tube in the stopper. Place the flasks in a 

 warm place and note the passage of gas bubbles 

 into the barium hydroxide solution. As these gas 

 bubbles (CO 2 ) enter, a white precipitate of barium 

 carbonate will form. The sucrase has been changed 

 to glucose and fructose and these sugars have been 

 fermented according to the following equation: 



FIG. S.-IODOFORM. (Autenrieth.) 



When the activity of yeast has practically ceased, connect the fermentation 

 flask with a condenser and distil the mixture. Catch the first portion of the dis- 

 tillate separately and test for alcohol by one of the following reactions : 



(a) lodoform Test. Render 2-3 c.c. of the distillate alkaline wtih potassium 

 hydroxide solution and add a few drops of iodine solution. Heat gentry and note 

 the formation of iodoform crystals. Examine these crystals under the microscope 

 and compare them with those in Fig. 8. 



(b) Aldehyde Test. Place 5 c.c. of the distillate in a test-tube, add a few 

 drops of potassium dichromate solution, KoCroOy, and render it acid with dilute 

 sulphuric acid. Boil the acid solution and note the odor of aldehyde changing 

 to that of acetic acid. 



TRISACCHARTOES, C 18 H 32 Oi 6 



RAFFINOSE 



This trisaccharide, also called melitose, or melitriose occurs in cotton 

 seed, Australian manna, and in the molasses from the preparation of 

 beet sugar. It is dextro-rotatory, does not reduce Fehling's solution, 

 and is only partly fermentable by yeast. 



Raffinose may be hydrolyzed by weak acids the same as the poly- 



