382 



Chemical C oiistitution of Starch [June-September 



and Duell was proposed by Rodewald. ^^ The determination of the 

 molecular weight was accomplished by means of the lowering of 

 the vapor pressure of water. The calculated value was 4370, equiv- 

 alent to (C6Hio05)27; the correct weight for this formula is 4374. 

 This reduction in size of the proposed molecular weight of 

 starch was reversed, however, two years later by Friedenthal/^ who 

 dissolved a commercial soluble starch (called ozone starch)- in 

 water and reprecipitated it with alcohol. This product showed, 

 by the freezing-point method, a molecular weight of 9450, which, 

 according to Friedenthal, corresponds with the formula 



In 1899, Brown and Millar^^ presented the results of several 

 years of further work upon the hydrolytic products of starch. The 

 main feature of their paper was the discovery of a reducing dex- 

 trin to which they gave the formula 39(C6Hio05) + (CgHiaOe), 

 or 4o(C6Hio05) + H2O. As the empirical formula indicates, it 

 might be made up by the condensation of forty glucose molecules 

 with the elimination of thirty-nine molecules of water, in accord 

 with the appended structural f ormulas : 



(I) 



CH2OH 

 I 

 CHOH 



I 

 /CH 



/ I 



/ CHOH 



O I 



\ CHOH 



\CH 



CH2 



I 



CHOH 

 I 

 /CH 

 O / I 



/ CHOH 

 O I 



\ CHOH 



\CH 



CH2 



I 

 CHOH 



CHOH 



O I 



CHOH 



I 

 CHOH 



I 

 CHO 



38 



(2) 



O C6H10O4 



I 



Oar (C6Hio04)38 



I 

 O 



CeHioOö <, 



( < signifies a free aldehyde group) 



11 Rodewald : Zeitsch. physik. Chcm., 1897, xxiv, p. 193. 



^2 Friedenthal : Centralb. f. Physiol., 1899, xii, p. 849. 



13 Brown and Miliar : Jour. Chem. Soc, 1899, Ixxv, p. 333. 



