106 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



Tanret (Compt. rend., 1909, cxlvii, 1775) treated raw starch for 30 minutes with a 

 cold 1 : 1000 hydi'ochloric acid, washing well with water, drying at 30 until the per cent 

 of water was reduced to 17, then heating at 100 to 110 for 1 hour in a closed vessel. This 

 solution was extracted with 25 per cent alcohol, which dissolved out about half of the 

 starch. About one-fourth of the residue was soluble, and it had a rotatory power (a)o = 

 + 188.6. Upon the addition of 95 per cent alcohol to an alcoholic solution, precipitation 

 occurred. The precipitate was washed with absolute alcohol, dried first over sulphuric 

 acid, and then at 100. The product was slightly soluble in boiling water, and had the 

 following rotatory power : {a)^ = +208 to 210. The insoluble portion gave an insoluble 

 blue compound with iodine and resembled the granular amylose of Maquenne and Roux. 

 The residue obtained by evaporating the alcoholic solution gave reddish-violet and red 

 reactions with iodine. (See Dextrins, page 120.) 



Welwart (Chem. Zeit., 1907, xxxi, 126) states that the easiest means of making 

 soluble starch is to boil a thin paste in a chamber with formic acid, which produces a more 

 limpid preparation than acetic acid. The acid is subsequently expelled by boiling. 

 Soluble starch may also be prepared by the action of sulphur dioxide at a temperature of 

 80 to 115, as was done, for instance, by Berge (Bull. Assoc. Beige d. Chimistes, 1897, 

 X, 444). He found that in the presence of either gaseous or liquid sulphur dioxide soluble 

 starch is produced at the above temperature, while at higher temperatures dextrin and 

 sugar may be formed (see pages 128 and 131). 



Skraup (Ber. d. d. chem. Gesellsch., 1899, xxxii, 2413) obtained by gentle acetylation 

 of starch a derivative which on saponification yielded a substance which resembled soluble 

 starch, giving a blue reaction mth iodine. Chlorine or chlorine-water were used by Siemens 

 and Halske (Jour. Soc. Chem. Industry, 1898, xvii, 257). By this method the starch is 

 made into a sludge and introduced into a vessel provided with stirring machinery. After 

 raising the temperature to 45 the starch is treated with chlorine or chlorine-water, the 

 product is then washed with water, and dried in the usual manner. The action of chlorine 

 leads to a partial rupture of the coats of the starch-grain, and the halogen enters the grain 

 and attacks boches wliich give to raw and bleached commercial starches an ethereal odor, 

 which are subsequently removed by washing with water. 



The chlorine process was modified by Hartwig (Jour. Soc. Chem. Industry, 1905, 

 xxiv, 1024), who subjected raw starch, especially corn starch, at a temperature of 50 to 

 86, to the action of an excess of cUorine for 4 to 8 days, or as long as necessary to render 

 the starch perfectly soluble in hot water. 



Gatin-Gruzewska and Maquenne (Compt. rend., 1908, cxlvi, 540) prepared soluble 

 starch by adding to a 3 per cent starch-paste one-fourth its volume of a hot 40 per cent 

 solution of potassium or sodiinn carbonate, and treating with one-thu'd its volume of 

 alcohol. A precipitate of " amylopectin " (see page 113) is tin-own down. The filtrate 

 contains a quantity of starch in solution. Or, 10 grams of potato starch are placed in 

 500 c.c. of a 1 per cent solution of sodium carbonate, sufficient water is added to make 

 1 liter, the preparation is neutralized with acetic acid, an equal volume of water added, 

 and the whole set aside for 24 hours. The filtrate contains starch in solution and 

 stains blue with iodine. Or, if starch be boiled with a concentrated solution of sodium 

 citrate or sulphate, and the mixture be filtered, the filtrate will be found to be rich in 

 soluble starch. 



Wolff (Jour. Soc. Chem. Industry, 1906, xxv, 437) treated starch at the ordinary 

 temperature for an hour and a half in double its weight of a solution consisting of 2 to 4 

 parts per 1000 of potassium bichromate and about 15 per cent of sulphuric acid. The 

 starch is then washed vmtil the excess of acid is removed, and then dried at a temperature 

 of about 30. The bichromate can be replaced by half its weight of permanganate. The 

 starch thus prepared forms a paste which, when heated in the presence of traces of basic 



