THE CHEMICAL CONSTITUTION OF STARCH 



A review 



ARTHUR W. THOMAS 



The size and configuration of the starch molecule have been 

 the subject of much chemical research since about 1836, when 

 Payen^ announced the chemical composition to be CgHioOg. This 

 is the empirical formula generally accepted at the present time. 

 The real molecular structure is known to be many times this 

 empirical unit, however. The highly colloidal nature of starch, 

 the ease with which it can be removed f rom its Solutions by merely 

 f orcing them through porous earthenware, and the extremely small 

 influence which it exerts on the freezing point of its solvent, are 

 facts that indicate a high degree of molecular complexity, which 

 probably approaches that of the proteins. 



The (CgHioOs)» structure indicates that starch is an anhydride 

 condensation product of glucose or maitose. This view is borne 

 out by the fact that hydrolysis by acid or diastase yields glucose or 

 maitose, respectively, as the end products. The contributions to 

 our knowledge of the molecular weight have all, or nearly all, de- 

 pended upon the study of the hydrolysis of starch by infusions of 

 malt, a type of study which has naturally been fostered by the 

 great fermentation industries. 



In 1860 Musculus^ noted that it was difficult, in fact quite im- 

 possible, completely to hydrolyze starch to maitose by means of 

 malt. After much experimenting he announced, in 1878 (Muscu- 

 lus and Grueber),^ his view that starch must be a Polysaccharide of 

 a molecular size indicated by the formula (Ci2H2oOio)5-6- In 

 1879 O'Sullivan* announced that the starch molecule is as large as 



1 Payen : Ami. Chim., 1836, [II] Ixi, p. 355 ; 1837, [II] Ixv, p. 225. 



2 Musculus: Attn. Chim., 1860, [III] Ix, p. 203; 1865, [IV] vi, p. 177. 



3 Musculus and Grueber : Bull. soc. chim., 1878, xxx, p. 54. 

 * O'Sullivan : Jour. Chem. Soc, 1879, xxxv, p. 770. 



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