CXCI.—The action of cold concentrated hydrochloric acid on starch and maltose

Arthur John Daish
1914 Journal of the Chemical Society Transactions  
WILLSTXTTER and Zechmeister (Ber., 1913, 46, 2401) have shown that whereas ordinary concentrakd hydrochloric acid (37.6 per cent. HC1) acts on cellulose a t the ordinary temperature relatively slowly, fuming acid (D 1*204-1-212; 39.9 to 41.4 per cent. HCl) dissolves cellulose within a few seconds and rapidly hydrolyses it, first to cellobiose acd finally to dextrose. After twenty-four hours the yield of dextrose is nearly quantitative. As the present methods of estimating cellulose in plant
more » ... lulose in plant material are of a highly empirical character, i t seemed probable that fuming hydrochloric acid might be applied with advantage to this purpose; it would, however, be necessary to allow for the sugars formed from the starch and pentosans present. There would be no difficulty in this, at3 methods for estimating these substances with a fair degree of accuracy already exist. As the action of the fuming acid on starch and maltose has not yet been studied, a series of experiments was first made in this direction, and the results are here recorded. The velocity of hydrolysis of starch and maltose by fuming hydrochloric acid is dealt with in a separate paper (p. 2065). When starch is left in contact, duqing several days, with dilute hydrochloric acid (7.5 per cent. HC1) it is converted, without dissolving, into the eo-called "soluble starch "; when heated with very dilute hydrochloric acid for several hours, dextrose is formed. The latter process has been applied very widely rn a means of astimating starch, although the fact that a considerable quantity of dextrose is destroyed renders such a method useless when any degree of. accuracy is required (Davis and Daish, J , .4yric. Sci., 1914, 6, 152). Early workers generally regarded the dextrose as formed directly from starch, and therefore looked upon the action of acids as essentially different from that of the enzyme diastase, the prolonged action of which on starch gives mainly maltose. Flourens, for instance (C'ompt. rend., 1890, 90, 1204), and Lintner and Dull (Bey., 1895, 28, 12) denied that m a l h is formed a t all by the
doi:10.1039/ct9140502053 fatcat:xzabsfhxxvhdncnraccw2zjfua