94 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



recorded that definite proportions of dextrin and sugar (2 : 1 or 1 : 1) are formed, the 

 starcli molecule being split by the agency of water into dextrin and sugar, and also that 

 two forms of dextrin occur, one of which is not colored with iodine. 



Griessmayer (Ann. d. Chem. u. Pharm., 1871, clx, 40) and Briicke (Sitzungsber. d. k. 

 Akad. d. Wissensch. z. Wicn, 1872, lxv, 3 Abth., 200), in independent investigations, ascer- 

 tained that two dextrins are produced which are readily distinguishable from one another 

 by their behavior with iodine. Griessmayer states that when the solution of starch is 

 set aside there will be formed at first a dextrin that is colored red with iodine, and then a dex- 

 trin that gives no color reaction with iodine but which nevertheless has the greater affinity 

 for tliis reagent. He designated these substances dextrin I and dextrin II, respecti\'ely. 



Briicke gave to the dextrin that becomes red in the presence of iodine the name crythro- 

 dextrin, and to the one which does not become colored, the name achroodextrin, both of 

 which terms have had almost universal use up to the present. He also noted that during 

 the conversion of starch into dextrin by the extract of malt a portion of the starch remains 

 after the disappearance of the granulose, which portion, like erythrodextrin, is colored 

 with iodine, but which shows a greater affinity for iodine than granulose. This substance 

 he termed enjthramyluvi, which he regarded as consisting of a mixture of Nageli's "cel- 

 lulose" and a substance which is colored red with iodine that is present in dry starch but 

 covered by the granulose, so that, as a consequence, its reaction is masked by the blue 

 reaction of the granulose. These dextrins, he found, did not reduce copper solutions. 



O'SuUivan (Jour. Chem. Soc. Trans., 1872, x, 579) at this time thought that the first 

 two dextrins are identical, and states that neither reduces a copper solution, and that they 

 possess a rotatory power (a)j = +213°. O'SuUivan, in referring to investigations of Muscu- 

 lus, Payen, and Schwarzer, in which it was found that dextrin and sugar are formed in about 

 equal proportions, or larger proportions of dextrin than sugar, showed by the copper test 

 for sugar that the proportion of non-reducing to reducing substance is 1 : 2. He, however, 

 did not regard the solution as being a solution of both dextrin and glucose, but as a solution 

 of a peculiar form of a sugar which he designated maltose. He showed that maltose is 

 not identical with glucose, because its reducing power corresponds to only GO per cent of 

 that of the latter, and he identified it with the sugar described by Dubrunfaut in 1823 

 (Ann. de chim. et phys., 1823, xxi, 178), who at that time stated that it was not glucose, 

 as was then believed. 



Several years later an important contribution by Musculus and Gruber appeared 

 (Zeit. f. physiolog. Chemie, 1878, ii, 177) which did more to mould our conceptions of the 

 processes and products of the saccharification of starch than any other single contribution 

 among the entire starch literature. They extended the investigation of Musculus of 1860, 

 working with starch in the presence of diastase, or dilute sulphuric acid under varying 

 conditions of time, temperature, etc., and recorded the formation of soluble starch, 1 ery- 

 throdextrin, 3 achroodextrins, 1 dextrin in small amount which is unconvertible into sugar, 

 maltose, and dextrose. The achroodextrins were found to differ in their rotatory powers and 

 reducing coefficients. These authors advanced the theory that the starch-molecule is broken 

 down through a number of well-defined stages by repeated hydrolysis; that at each stage 

 there is produced coincidently a form of dextrin together with maltose; that with each suc- 

 ceeding stage there is formed a dextrin of lower molecular weight than the preceding, and 

 that ultimately there is present a small amount of unconvertible dextrin together with mal- 

 tose and glucose (see page 122). These authors failed to give evidence that they had studied 

 pure substances, and it was shortly afterward demonstrated by Brown and Morris (Ann. d. 

 Chem. u. Pharm., 1885, xxiii, 72) that the distinctive properties of the different achroodex- 

 trins, as stated by Musculus and Gruber, could be accounted for upon the assumption of vari- 

 able mixtures of maltose and a single achroodextrin that had not reducing power, although 

 they also held that a specific body exists in the form of maltodextrin (see page 124). 



