VOLUMETRIC ESTIMATIONS 



Esiitnatton of Cane Suga): 



Cane sugar does not reduce Fehling's solution ; it is there- 

 fore necessary to invert it in order to make the estimation. To 

 do this, take a known volume of the sugar solution and add a 

 sufficiency of strong hydrochloric acid to make it about a lO 

 per cent solution of the acid ; heat on a water bath for about 

 a quarter of an hour, at 70° C. Then neutralize with sodium 

 carbonate, make up to a known volume and titrate. 



The inversion of cane sugar may be represented thus : — 



CiaHaaOn + H^O = CgH.sOe + CeHijOg 



The molecular weight of cane sugar is 342, and the amount 

 of invert sugar this will give on inversion is, from the equation, 

 360. In other words, i gram of glucose corresponds to §4f 

 = "95 gram of cane sugar. The titration result must therefore 

 be multiplied by "95. 



Estimation of Maltose. 



Three points must here be remembered : firstly, that 

 maltose will reduce Fehling's solution ; secondly, that this 

 reduction may not be complete, and therefore the maltose 

 must be inverted before it is titrated ; thirdly, that the re- 

 ducing power of maltose is not the same as glucose, i gram 

 of maltose having the same reducing power as '62 gram of 

 glucose. From the equation representing the inversion of 

 maltose, it may be found that i gram of maltose gives i '05 

 gram of glucose ; and, as i gram of maltose has the same 

 reducing power as "62 gram of glucose, it follows that i 

 gram of maltose after inversion gives an increased reducing 

 power, viz. : — 



1*05 --62 ='43 gram glucose, 

 •*• '43 gram glucose = i gram maltose, 



and I gram glucose = — gram maltose, 



= 2-32 grams maltose. 



The titration result, which represents glucose, must therefore 

 be multiplied by 2-32. 



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