122 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



gives no sugar reaction. Later, the iodine will not yield a color reaction, while Fehling's 

 solution is reduced. There is in solution, then, a substance that has great affinity for iodine, 

 greater than dextrin I, which has lost its dextrin color-reaction characteristics towards iodine, 

 yet without having acquired the distinguishing marks of sugar. Tliis dextrin he names dex- 

 trin II. He believed that both dextrins coexist in fresh starch solution in small quantities. 



O'Sullivan (Jour. Chem. Soc. Trans., 1872, 579) also noted the existence of two 

 dextrins, which he distinguished as a- and /3-dextrins, respectively, and which correspond 

 with the dextrin I and dextrin II of Griessmayer. O'SulUvan found that both forms are 

 changed into maltose by diastase or dilute acid, and that both have the same rotatory 

 power, (a)j = +213. He prepared them almost free of reducing power, and suggests that 

 if pure they would not reduce copper solutions. There appeared at the same time a very 

 elaborate contribution by Briicke (Sitz. d. k. Akad. d. Wissensch., Wein, 1872, lxv, 3 

 Abth., 126) on the manner of digestion and assimilation of carbohydrates. He noted 

 two dextrins, corresponding with those recorded by Griessmayer and O'Sullivan. The 

 dextrin which gives a red reaction with iodine he termed erythrodexirin, and the one which 

 did not give a color reaction he termed achroodcxtrin, which terms have continued in uni- 

 versal use to the present. Besides these dextrins there was found a residue which Briicke 

 named erythamylum, which he states consists of Niigeli's cellulose together with a substance 

 which takes a red stain with iodine, which is already present in dry starch, but which is 

 masked by the granulose and its blue reaction with iodine. 



A study of amylodextrin, together with a comparison of the properties of starch, 

 amylodextrin, and dextrin, was made by W. Niigeli (Beitrage z. niiheren Kenntnis d. 

 Starkegruppe, etc., 1874, Leipzig), in wliich he refers to the existence of two forms of 

 dextrin, one of which is colored red or orange and the other yeUow with iodine. He asserts 

 that there is no dextrin which does not become colored with iodine, and also that Mus- 

 culus's theory of the breaking up of starch coincidently into dextrin and sugar does not 

 hold. Three dextrins, a, /3, and r, were described by Bondonneau (Compt. rend., 1875, 

 Lxxxi, 972, 1210). The a-dextrin corresponds with the dextrin I of Griessmayer, ery- 

 throdextrin of Briicke, and the a-dextrin of O'Sullivan; while the |8-dextrin corresponds 

 with dextrin II of Griessmayer, the achroodextrin of Briicke, and the /3-dextrin of O'Sulli- 

 van. The next year, 0-Sullivan (Jour. Chem. Soc, 1878, i, 479) gave good evidence to 

 show that the r-dextrin of Bondonneau does not exist, and that the latter was led into 

 error because of the assumption that the sugar product is dextrose, and that the r-dextrin 

 is merely an expression, not recognized by Bondonneau, of the difference between the 

 reducing powers of maltose and dextrose. Nasse (Acliiv f. ges. Physiologic, 1877, xiv, 

 473) beUeved by the action of saliva or dilute sulphuric acid that there are formed dcx- 

 trinogen (achroodextrin) and also a pecuUar form of sugar that is not grape sugar, and which 

 he i^roposes to distinguish by the name amylum ptyalose. 



Thus far it had been clearly shown by a number of investigators that two very dififerent 

 forms of dextrin are produced during the saccharification of starch, but Musculus and 

 Gruber (Zeit. f. physiolog. Chemie, 1878, ii, 177) were the first to give evidence to lead to 

 the belief that the so-called achroodextrin is not an individual, but a mixture of at least 

 three achroodextrins which have different optical and reducing powers. Based upon the 

 results of their research, they formulated a definite theory of the processes and products 

 of starch saccharification, which with certain modifications has received a very general 

 acceptance from that time to the present. According to these authors the derivatives 

 of starch by the action of diastase or weak sulphuric acid are as follows : 



(1) Soluble starch. [Probably a peculiar form of starch or of erythrodextrin.] It is insoluble 

 in cold water, and soluble in water at 50 to G0. An aqueous solution gives a wine- 

 red reaction with iodine. Dried in the air it will give a violet, j-ellow, or bro\vn with 

 an excess of iodine. Its specific rotatory power is (a) = +218, and its reducing power 6. 



