E.— CHEMISTRY. 45 



Karrer rapidly changed his views in favour of an alternative which 

 is equally incorrect. The unit he prefers at present is: — 



,— CH 



I CHOH ' 



I I 



CHOH 



I 

 -CH 



CHOH i 



I ; 



CHj CH • CHOH -CHOH • CH • CHOH • CH, 



O 



XXI. 



I o ' 



It is clear that the only trimethyl glucose to which such a structure 

 could give rise is the 2,3,5-form described by Irvine and Oldham.-^ 

 No trace of this compound was detected by us, and, moreover, the 

 2,3,6-variety of trimethyl glucose actually obtained cannot possibly 

 be accommodated by Karrer's formula. For similar reasons it can no 

 longer be maintained that starch is an aggi-egate of (J-glucosan residues. 

 Irvine and Oldham have proved that glucosan is convertible into 

 2,3,5-trimethyl glucose, and the same sugar should be formed on 

 hydrolysing methylated starch if there is any structural relationship 

 between glucosan and the polysaccharide. The result obtained is 

 obviously opposed to such a view. 



Our work has also thrown light on various other problems connected 

 with the chemistry of starch, including the attachment of niti'ogen and 

 phosphorus to the molecule. These elements do not appear to be 

 constituents of extraneous compounds, but form part of the polymerised 

 aggi-egate. This is shown very clearly by the behavio'ur of nitrogenous 

 starch, which was methylated in the first instance by the use of methyl 

 sulphate and alkali. Thereaiter the product was treated with silver 

 oxide and methyl iodide, but contrary to expectation the whole of 

 the material became converted into an insoluble additive compound 

 with silver iodide. This behaviour does not extend to a purified starch, 

 and finds an exact parallel in the case of glucosamine derivatives which, 

 under identical conditions, form insoluble complexes with silver 

 halides.-'' Obviously if nitrogen were present merely as part of an 

 adventitious impurity only this component would be removed in the 

 course of the silver oxide alkylation, and the fact that the total material 

 was preci^^itated is a proof that the fragment containing nitrogen is 

 definitely polymerised to the starch unit. Similar considerations apply 

 to the case of glycogen and have served to complicate onr work on the 

 alkylation of this compound. It has been established, however, that, 

 as in the case of starcli, the metliylation of glycogen shows a. tendency 

 to be aiTested when the metlioxyl content is under 40 per cent. The 

 separation of the methylated glucoses is not yet sufficiently far advanced 

 to permit of their identification, but a publication on the eicact relation- 

 ship of glycogen to starch will not be long delayed. 



