iQii] Ernest D. Clark 205 



III. SUMMARY OF GENERAL CONCLUSIONS 



The amount of reducing power of Lintner soluble starch, and 

 the intensity of its erythrodextrin coloration with iodine Solution, 

 appear to be proportional, in a general way, to the acidity of the 

 product. 



By dialysis, aqueons Solutions of Lintner soluble starch yielded 

 to the diffusates considerable material possessing strongly marked 

 reducing action and erythrodextrin properties. There was equiva- 

 lent diminution in the proportions of reducing substances and ery- 

 throdextrin in the starch that remained in the undiffused residual 

 liquid in these cases, though never complete removal of either.^^ 



Our best preparations of Lintner soluble starch were made from 

 potato starch of our own production. It is possible that the method 

 of manufacturing the available commercial potato starch included 

 an influence that was responsible for the difference noted. 



The reducing power of a given preparation of Lintner soluble 

 starch is largely, perhaps wholly, due to contained dextrins, from 

 which the product can be purified only with the greatest difificulty, 

 if at all. Consequently, it is not strictly justifiable to correct for 

 this reducing power in diastatic determinations as Meyer^^ did, by 

 subtracting the weight of cuprous oxide produced through the action 

 of the soluble starch alone, from that of the cuprous oxide formed 

 by the products of enzyme action upon the starch. Whether the 

 original reduction in such cases is induced by traces of dextrins 

 or not, it seems that this reduction represents material which may 

 be further acted upon and removed by the enzyme, with the forma- 

 tion of maltose and other products of such action. Therefore, 

 although the original reduction indicates the amount of reducing 



" These conclusions accord with the view of Brown and Morris (Journal of 

 the Chemical Society, 1900, Iv, p. 449), who consider that the reducing power of 

 Lintner soluble starch is due to the presence of certain dextrins, which cannot be 

 completely removed either by dialysis or precipitation. 



Just as this work was nearing completion, it was discovered that Ford (Jour- 

 nal of the Society of Chemical Industry, 1900, xxiii, p. 415) had dialyzed Lintner 

 soluble starch and had, in one or two details, anticipated our results. He stated 

 that his dialysates contained material which gave a reddish brown coloration with 

 iodine and which also possessed reducing power. Since his dialysates were 

 evaporated at boiling temperature, it was impossible for Ford to say that this 

 material was not produced by hydrolysis. 



" Meyer : Loc. cit. \ 



