39^ Chemical Constitution of Starch [June-September 



In 1905, Skraup,^^ working along similar lines, acetylated dex- 

 trins and starch derivatives under the influenae of hydrochloric 

 acid gas at — 20° C. From a study of some of the chloracetyl 

 derivatives he announced his behef that starch has a molecular 

 weight of (CcHio05)46 to (C6Hio05)5o. 



A method altogether different in principle from those preceding 

 was pubHshed in 1909 by Wacker. ^^ The procedure consisted in 

 mixing the substance to be investigated with Phenylhydrazine sul- 

 fonic acid and alkaH, when a red color was formed, the depth of 

 color depending upon the molecular weight. This method worked 

 very well with carbohydrates and Compounds having alcohol and 

 aldehyde groups. Wacker's conclusion, however, that starch is 

 made up of two substances, one (CgHioOg)« and another "of a 

 more cellulose character," (CeHioOg)^ to (CgHio05)s, indicates 

 that his method does not hold in the case of starch Solutions. 



It is very stränge that many modern chemists, or chemists liv- 

 ing in modern times, still seem to think that starch has a low molec- 

 ular weight. The large amount of trustworthy experimental evi- 

 dence which has been reported in the last fifteen years ought to 

 dispel such a notion. Nevertheless, in a recent review, Frank- 

 forter^''' seriously considered such formulas as (C6Hio05)2, 

 (^eHioOg)^, and (C6Hio05)6, giving his preference to the "hexa- 

 polymer." He cited Wacker's experiments, drawing from them 

 the conclusion that " the starch molecule is at least of the size 

 (CßHi 005)6 or probably greater." He included a graphical for- 

 mula, made up of six glucose groups united by oxygen linkings in 

 a continuous structure. 



Such a simple structure seems quite impossible. Malt hydrol- 

 ysis of starch results in the formation of maitose and of dextrin 

 of great complexity. We feel confident that malt diastase as ordi- 

 narily used is a hydrolyzing and not a constructive agent. Where 

 could the complex dextrinous substances come from if the starch 

 molecule were a simple hexapolymer of glucose? Does not also 

 the colloidal nature of starch in Solution suggest a high molecular 

 weight ? 



25Skraup: Monatsh. Chem., 1905, xxvi, p. 1415. 



26 Wacker : Berichte, 1909, xlii, p. 2695. 



^'^ Frankfurter : Proc. 8th Intern. Congr. Appl. Chem., 1912, viii, p. 133. 



