<J4 A TEXTBOOK OF PHYSIOLOGY 



split by weak organic acids such as citric and tartaric. This process, 

 one of hydrolysis, is sometimes termed inversion owing to the fact that 

 cane-sugar before hydrolysis is dextrorotatory, but after hydrolysis 

 is levorotatory. In the case of maltose and lactose the term is also 

 employed, but no inversion of polarized light takes place on hydrolysis ; 

 maltose gives a considerable fall, lactose a slight rise, in rotating 

 power after " inversion." 



None of the disaccharides yields Barfoed's test. 



Cane-sugar, or saccharose, occurs widely in the plant world, very 

 abundantly in the sugar-cane and the sugar-beet. It possesses a 

 distinctly sweet taste, is easily soluble in water, but with difficulty in 

 alcohol. Its rotatory power is 66-5 before, and - 20 after, inversion. 

 In other respects it gives few positive tests. It does not give 

 Moore's test nor the ordinary reducing tests. It gives no osazone. 

 It does not ferment with yeast until inverted. 



THE REACTIONS OF MONOSACCHABIDES AND DISACCHARIDES. 



Dextrose. Levulose. Galactose. Maltose. Lactose. 



Cane- 

 Sugar. 



Moore's test 

 (KOH) 



Trommer's test 

 (CuS0 4 +KOH) 



f 



+ ve 



33% 



weaker 



-f ve 

 26-5% 

 weaker 



than D. than D. 



Fehling's test + + + + + 



(CuS0 4 +KOH+ 

 Rochelle salt) 



Nylander's test -I- + + + + 



(bismuth sub- 

 nitrate -1- KOH + 

 Rochelle salt) 



Barfoed's test (acid + + + 



cupric acetate) 



Phenylhydrazine Long thin Long thin Long thin Short Yellow 



test (Osazone needles needles needles thick rosettes 



crystals formed) M.P. 204 M.P. 204 M.P. 186 needles M.P. 201 



M.P. 206 



Rotary power on +52-7 -93 +81 +137 +52-5 +66-5 



polarized light 



Effect of hydro- Marked Slight Inverted 



lysis on rotary fall rise to 20 



power to the left 



Yeast fermentation Marked Marked Very Marked Nil Marked 

 test little after 



inversion 



Solubility in alco- + . . Insol. 1 



hoi; cane-sugar =1 



I I 



