iQii] Ernest D. Clark i95 



sequently, Meyer discovered that his preparation of Lintner solu- 

 ble starch possessed striking reducing power. He concluded from 

 this fact that soluble starch is a reducing substance. Accordingly, 

 he subtracted from the weight of the cuprous oxid obtained in his 

 later diastatic determinations the weights of the cuprous oxid 

 that the employed amounts of Lintner starch were initially able to 

 precipitate from Fehhng Solution under the conditions of the uni- 

 form reduction tests.^ 



Prior to the pubHcation of Meyer's results, we were under the 

 impression that true sokible starch is devoid of reducing power. 

 Lintner's method for the preparation of soluble starch appeared to 

 US to yield a crude product. Meyer's preparations of Lintner 

 soluble starch seemed to be mixtures of substances. We under- 

 took this work for the purpose of ascertaining the facts in these 

 and related connections. 



We prepared Lintner soluble starch in accordance with the 

 directions published by Meyer,'* which, although detailed, are not 

 always clear. On this account our procedure may have differed 

 here and there from Meyer's, but we are confident that any such 

 unavoidable variations were too slight to influence the results to 

 any material extent. 



IL EXPERIMENTAL 



I. Origin of the potato starch employed in these experi- 

 ments. Our preparations of soluble starch were made from com- 

 mercial potato starch and also from starch obtained by us from 

 potatoes.^ The latter preparations were made by macerating pota- 

 toes on a grater, thoroughly mixing the pulp with an excess of 

 water, then straining the milky liquid through muslin and finally 

 allowing the starch to settle out. The starch sediment was freed 

 from the supernatant extract by decantation, then washed with about 



* It is evident that such a subtraction was warranted only if the reduction 

 was due to an impurity that neither gained nor lost reducing power as hydrolysis 

 progressed. Meyer, however, attributed the reducing power to the Substrate 

 itself, and not to an impurity. 



* Meyer : loc. cit. 



' By making our own starch we sought to eliminate the influence of any 

 impurities that might be introduced into commercial starch by processes of 

 manufacture. 



