120 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



per cent by FrohbciTy yeast, while the same form of dextrin prepared by Griiters by means 

 of oxalic acid was fermented only to the extent of 24 per cent. In a subsequent communi- 

 cation (Z. Spiritusind, 1907, xxx, 371) Rheinfeld noted that a certain amount of the prod- 

 ucts of hj'drolysis undergo polymerization and condensation when a solution is repeatedly 

 evaporated. He carried on hydrolysis until no color reaction with iodine was obtained, 

 and by repeated fractionation he prepared 5 specimens of maltodextrin 7. The constants 

 he records as (a)D = +163-167 and i2 = 58— 62. Griiters' values were (a)D = +lGO and 

 R = Gl. WHien determined as Ost's glucose values, when corrected, the values were (a)D = 

 + 170-173 and J? = 61 -64. 



Reichard (Zeit. ges. Brau. 1908, xxxi, 161) confirmed Syniewski's statement in regard 

 to the formation of a formaldehyde-amylodextrin compound by the action of concentrated 

 formaldehyde. He studied the influences of different percentages of formaldehyde in 

 relation to consecutive changes in the starch, and also its influence upon the temperature 

 of gelatinization ; a gram of starch was completely gelatinized by 10 c.c. of a 37 per cent 

 unneutralized formaldehyde in 7 to 8 hours at 25°. With weaker or neutralized formalde- 

 hyde, and at lower temperatures, the action is slower. At 15° to 16° the starch was gelatin- 

 ized in 38 per cent formaldehyde in 2 days. The formaldehyde preparations give at first 

 a blue reaction with iodine, but when the gelatinous stage is reached the reaction is 

 brownish-red ; and the gelatinized starch dissolved in water yields a yellow reaction, which 

 indicates a further reaction of the formaldehyde. 



Castoro (Gas. chim. Ital., 1909, xxxix, 603) heated pea starch for 5 hours in a 2 per cent 

 sulphuric acid, filtered, and precipitated with alcohol. Upon treating the precipitate with 

 water one part was found to go into solution and another to remain undissolved. The latter 

 gave a blue-violet reaction with iodine, and corresponded with the amylopectin of Maquenne 

 and Roux. Upon dialyzing the part in solution two fractions could be obtained, one giving 

 a blue reaction with iodine and the other a violet reaction corresponding to that of amylo- 

 dextrin. By dialyzing a pseudo-solution of potato starch prepared by the agency of 1 per 

 cent sulphuric acid, a diffusible portion was obtained that gave a violet reaction with iodine. 

 He believes that the differences in the color reaction are due to differences in the size of the 

 particles, the large particles becoming blue and the small particles violet. It is pointed 

 out that analogous differences may be observed in gold-colloidal solutions. 



ERYTHROUEXTRIN, ACHROODEXTRIN, GRENZDEXTRIN, ETC. 



Although Vaquelin (Bull, de pharm., 1811, in, 54) noted that when starch is subjected 

 to torrefaction it is converted into a gum-like substance, and Vogel (Schweigger's Jour., 

 1812, V, 80) that starch is changed by weak acid into gum and sugar, and various experi- 

 menters of the following twenty years that starch yields a gummy substance, it remained 

 for Biot and Persoz (Ann. de cliim. et phys., 1833, lii, 72) to demonstrate the distinguishing 

 characters of this substance, and to give it the name by wliich it has continued to be known 

 even to the present day. They believed that it existed as a constituent of the grain, 

 and that it is Uberated by boiling in water or by weak solution of acid, which disrupts 

 the outer coating of the grain. From its strong dextro-rotatory action on rays of plane 

 polarized light they named it dextrin. The same year, Payen and Persoz (Ann. de 

 chim. et phys., 1833, liii, 73) prepared dextrin by the aid of diastase. They ascertained 

 in these experiments that a number of substances were present in the preparations — 

 one of them was insoluble in cold water, but soluble in hot water, and colored with 

 iodine, and identical with the substance of the interior of the starch-grains; a second 

 substance, which is soluble in both cold and hot water and in weak alcohol, but not 

 colored with iodine, and in the nature of a gum; and a third substance, sugar, etc. This 

 second substance is the body they named dextrin, and corresponds with the achroo- 

 dextrin of the present. 



