Errors of Munson and Walker's reducing-sugar tables and the precision of their method

Abstract

In a r ecent investigation (RP1301) Hammond has undertaken a comprehensive revision of the Munson and Walker reducing-sugar tables and has disclosed discrepancies much greater than the experimental errors of analysis. It is now shown that the main cause of these discrepancies was the contamination of the cuprous oxide, which Munson and Walker weighed directly for the estimation of copper. An independent series of analyses made by the amthors, who determined copper iodometrically, was found to be in good agreement with the analyses of Hammond, who determined the copper electrolytically. The recommendation is made that Hammond's copper equivalents be adopted in substitution of those of Munson and Walker.A series of determinat,ions by Erb and Zerban of invert sugar in the presence of sucrose in aliquots containing 0.4 g of total sugars in 50 ml of solution are in agreement with those of Hammond at high concentmtions of invert sugar, but deviate at lower concentrations. The present series of analyses are in agreement with those of Hammond at these discrepant points.Detailed methods of copper analyses are described. A new modification of the dichromate method is given in which the end point is determined both colorimetrically and electrometrically.Methods for the preparation of standard invert sugar by hydrolysis of sucrose are discussed. CONTENTS