132 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



the action at the proj^er time, and then precipitating the special dextrin by means of a 

 proper neutral saline. Preparations of different dextrins were also made from commercial 

 dextrin. Tlu-ee forms of erythrodextrin were investigated. Erythrodextrin I was pre- 

 pared from either commercial dextrin or a starch-digestion by saturating with magnesium 

 sulphate, wasliing the precipitate with a saturated solution of this salt, dissolving the pre- 

 cipitate in water, and then removing any soluble starch that may be present by half satura- 

 tion with ammonium sulphate. The filtrate gives a bright reddish-purple (almost magenta) 

 without any preliminary blue, irrespective of the quantity of iodine. This iodide of dextrin, 

 they state, is thrown down upon saturation with ammonium sulphate in the form of a darker 

 reddish-purple precipitate. Erythrodextrin II was obtained by saturating a solution of 

 the mixed products with magnesium sulphate, filtering off the soluble starch and the ery- 

 throdextrin I that are jirecipitated, and then saturating the filtrate with sodium sulphate 

 at 33. A solution of this last precipitate gives a reaction with iodine varying from a 

 bright reddish-purple to mahogany-red. Young states that this dextrin may be made up 

 chiefly of erythrodextrin I, but that this is improbable. Erythrodextrin Til was prepared 

 by the spontaneous precipitation of the filtrate obtained after saturation as above of a 

 solution of commercial erythrodextrin or a starch-digestion. This substance gives a red 

 or purple reaction with iodine. If the salt had not dialyzed away previously and the iodine 

 had been added, the filtrate, which at first is reddish-brown, becomes opaque, turbid, and 

 brownish-black or of even a greenish tinge, and on standing a dark-blue precipitate is 

 thrown down. If this precipitate is collected on a filter and dried it becomes reddish- 

 brown; and if dissolved in water it forms a blue solution, which instantly changes to 

 the red-brown characteristic color of this erytlirodextrin, the solution now behaving as an 

 ordinary solution of iodide of erythrodextrin III. 



Young notes that glycogen gives a color reaction very closely similar to that of erythro- 

 dextrin III, but that it can readily be distinguished from this dextrin by differences in its 

 behavior with neutral salts. Achroodextrin was prepared by allowing diastase or dilute 

 acid to act on starch-paste to a stage beyond the achromic point in relation to iodine. The 

 action was stopped by boiling or by neutralization. The dextrins were precipitated by 

 alcohol, collected, washed, dissolved in water, and then boiled on a water-bath to expel 

 the alcohol. The solutions were cooled and treated in the usual way by saturation with 

 neutral saline. Achroodextrin gives a very slight precipitate on saturation with annnonium 

 sulphate, but it is doubtful, it is stated, if the precipitate is actually achroodextrin. Yoimg 

 notes that erythrodextrin so-called is really a series of bodies quite distinct from either 

 starch or the achroodextrin, and that the three products he distinguishes as erythro- 

 dextrin I, II, and III give reactions closely similar to the corresponding products described 

 by Lintner and Dtill and obtained by other methods. 



A method for separating dextrin from soluble starch was reported by Hefelmann and 

 Schmitz-Dumont (Zeit. f. offentl. Chem., 1S9S; Chem. Centralbl., 1898, ii, 5G1) by which, 

 for instance, 5 grams of commercial dextrin are dissolved in 250 c.c. of cold water and placed 

 in a flask of slightly greater capacity, to which solution is added 18 c.c. of ether, and the 

 flask stoppered and shaken. The contaminating starch separates as a flocculent precipitate, 

 while the dextrin remains in solution. If sugar and soluble salts are present thej^ will 

 remain in solution with the dextrin. 



Starch-paste was liquefied and converted into dextrin without the formation of sugar 

 by Pottevin (Compt. rend., 1898, cxxvi, 1218) by the action of malt extract that had 

 been kept for 15 to 20 minutes at a temperature of 79 to 80. A 10 per cent solution of 

 starch was subjected for 12 hours at G0 to malt extract that had thus been heated; and 

 the solution was fractionated with alcohol into 3 portions. The first portion, or least soluble, 

 gave with a trace of iodine a blue reaction, but a violet-brown with an excess; the second 

 portion gave a reddish tint; and the third portion no coloration. In none was any sugar 



