114 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



and dextrin, or a mixture of the two, and it has been used in both senses, but it has also 

 been employed synonymously with soluble starch and maltodextrin, the former being 

 the fii'st dissolution product of ordinary raw starch, while the latter is one of the later prod- 

 ucts of digestion; and it has been given to various intermediate products between true 

 soluble starch on the one hand and sugar on the other, products giving reactions with 

 iodine ranging from a purple and bluish-violet to wine color, brownish-red, or reddish- 

 yellow, and even to some giving no color reaction. It is obvious, from the foregoing, that 

 the word does not designate any specific individual or mixture, but some indefinite starch- 

 like or dextrin-like or dextrin-sugar substance or compound or mixture that may be formed 

 or exist during the saccharification of starch at any time between the moment of solution 

 of starch-grain and the final stage of dextrin digestion. The same statement (with modi- 

 fications) holds true in regard to maltodextrin. In quoting the literature the terms amylo- 

 dextrin and maltodextrin will be used as the various authors use them. 



It is probable that Jaquelain (Ann. de chim. et phys., 1840, lxxiii, 167) was the earliest 

 observer to specifically note the existence of a body having the characteristics of amylo- 

 dextrin; that is, of a body or compound or mixture having intermediate properties between 

 soluble starch and dextrin, which gives a purple or violet reaction with iodine. He records 

 that after treating starch with water at 150, and then cooling, there separated round 

 grains wliich gave a purple coloration with iodine. He also makes note of preparing a 

 precipitate in the form of a powder that gave the same reaction. This or a closely 

 related substance was probably described by Musculus (Compt. rend., 1870, lxx, 857), 

 at first under the name of insoluble dextrm. In a later article (Bull. Soc. chim., Paris, 

 1874, XXII, 26) it is described under the name amidon soluble. 



W. Nageli (Beitrage z. naheren Kenntnis d. Stiirkegruppe, Leipzig, 1874) seems to 

 have been the earliest investigator to make a serious study of amylodextrin; that is, of a 

 body that stands between soluble starch (which gives a blue reaction with iodine) and 

 erythrodextrin (which gives a red reaction). He treated raw starch with weak acids in 

 the cold for many days, and found that a substance (amylodextrin) goes into solution 

 which the acid soon changes into dextrin and sugar. The starch-grains undergo a slow 

 but complete solution, the periphery being the last to dissolve; but the grain residues yield 

 amylodextrin as long as they give a color reaction with iodine, even though the reaction 

 be a yellow. Amylodextrin crystallizes in small flakes on evaporation, or by freezing, 

 or by tlie addition of alcohol. According to Nageli the flakes consist of small needles 

 which are associated in the form of radial aggregates which resemble crystals of inulin. 

 It is insoluble in cold water, but is readily soluble in water at 60, this solution remaining 

 clear upon cooling. A freshly prepared precipitate by means of alcohol is readily soluble 

 in cold water. It does not itself possess the property of dialyzability, but is dialyzable 

 when accompanied by dialyzable substances. It has lower rotatory power than starch, 

 but higher than erythrodextrin, and it hkewise stands between starch and erythi'odextrin 

 in its behavior toward alcohol and baryta-water, and in its affinity for iodine. It consists 

 of two modifications, neither of which in a soUd state is colored with iodine, but which 

 when in solution become violet and red, respectively. The rotatory power he gives as 

 (a) +175 -177. The soluble starch described by Musculus and Gruber (Zeit. f. pliy- 

 siolog. Chemie, 1878, ii, 177) was misnamed and corresponds with the amylodextrin of 

 Nageli, but is not identical. These authors recorded the product as being insoluble in 

 cold water, soluble in water at 50 to 60, and in aqueous solution giving a wine-color 

 reaction, or when dry a violet, yellow, or brown reaction in the presence of an excess of 

 iodine. The specific rotatory power is given as (a) +218. 



Herzfeld (tjber Maltodextrin, Halle, 1879) opposed the view of the splitting of the 

 molecules of starch into dextrin and maltose according to the theory of Musculus, and held 

 that there is a consecutive conversion of soluble starch into erytlu-odextrin, achroodextrin, 



