. Smithsonian miscellaneous collections. certain analytical techniques, , the hydrolysisof disaccharides and polysaccharides by strong hydrochloric error is occasioned also by the amounts of sodium fluoridesometimes added for preservation of biological extracts. 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO4 Sodium sulfate, potassium sulfate (fig. 1).—According to Somogyi(1937), sulfate has a manifold effect upon the copper reduction. Onthe one hand it tends to increase the reduction equivalents by de-pressing the solubility of oxygen in the reaction mixture, and bydecre
. Smithsonian miscellaneous collections. certain analytical techniques, , the hydrolysisof disaccharides and polysaccharides by strong hydrochloric error is occasioned also by the amounts of sodium fluoridesometimes added for preservation of biological extracts. 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO4 Sodium sulfate, potassium sulfate (fig. 1).—According to Somogyi(1937), sulfate has a manifold effect upon the copper reduction. Onthe one hand it tends to increase the reduction equivalents by de-pressing the solubility of oxygen in the reaction mixture, and bydecreasing the alkalinity of the solution through suppression of theionization of the carbonate; on the other hand it decreases the rateof reduction so that in a given time the reaction is nearer completionin the absence of sulfate than in its presence. Under our conditions,the last effect appears to predominate. The effect of potassium sulfate(not shown in fig. 1) is identical with that of sodium sulfate. __ — -a NoCI IT— — • NaF. NaNQj - .4 .6 .8 MOLAR CONCENTRATION Fig. 1.—Effects of sodium fluoride, sodium chloride, potassium chloride, sodium nitrate, and sodium sulfate on estimation of glucose by copper ( ) and ferricyanide ( ) reagents. The effect of alkali sulfates upon oxidation by the ferricyanidereagent is practically identical with that of the halides. Sulfate is sometimes used to precipitate lead from sugar solutionswhich have been clarified by this metal. A large excess of sulfateshould be avoided. Sulfate is introduced into sugar solutions alsoby the use of sulfuric acid for hydrolysis of carbohydrates. Sodium nitrate (fig. 1).—This salt produces effects on both reagentssimilar to those given by halide and sulfate. Calcium chloride, magnesium chloride, magnesium sulfate (fig. 2).—These salts cause a marked diminution of the copper reduction, pre-sumably owing chiefly to precipitation of carbonate and consequent NO. 10 SUGAR DETERMINATION WEINTRAUB A
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