NOTE 515 



treated with 20 c.c. of o-i N iodine solution and 5 c.c. of 0-5 N 

 sodium hydroxide, the temperature being kept at 5° C. ; * 

 after forty-five minutes the mixture was acidified by the ad- 

 dition of 5 c.c. of 2 N sulphuric acid and the excess of iodine 

 titrated with -05 N sodium thiosulphate. 



The equation representing the change is as follows : — 



QHi.Os -1-12 + sNaOH = QHnOaCOONa + 2H,0 + 2NaI. 



Sodium gluconate. 



The proportions of glucose {x) and fructose (y) can then 

 be determined from the equations : — 



Cx + C^y = iodine equivalent of the solution. 

 Kx + K^y = reducing power of the solution. 



in which K and Ki represent the grams of CuO equivalent to 

 I gram of glucose and fructose respectively, at the dilution 

 used (as obtained from Lane and Eynon's tables), and C and 

 Ci represent the grams of iodine equivalent to i gram of 

 glucose or fructose respectively, namely 1-404 arid 0-02. 



The iodine titrations must be carried out on cleared un- 

 inverted solutions as citric acid vitiates the results. 



* At this temperature the oxidation of fructose is small. 



33 



