SOLUBLE STARCH. 107 



matter, as, for instance, tap-water, becomes fluid and transparent. The liquefied paste 

 gradually gelatinizes when cooled, but is readily liquefied by heating. If the prepared 

 starch be washed in distilled water instead of tap-water containing traces of basic sub- 

 stances, and dried at 30°, it may be converted into soluble starch by heating in the dry 

 state at 80° to 100° for a few hours. 



Starch may be liquefied by boiling in a weak solution of aluminum chloride (Jour. 

 Soc. Chem. Industry, 1901, xx, 492). The starch is boiled in the solution of aluminum 

 chloride in a similar manner to that followed when dilute acids are emploj^ed, and the 

 aluminum may be separated by the subsequent addition of sodium silicate. The use of 

 aluminum chloride prevents the extraction of objectionable nitrogenous matter from the 

 grains. Hydrogen peroxide and ammonia were used by von Asboth (Chem. Zeit., 1892, 

 XVI, 725) to prepare a soluble starch, which he called amylodextrin. This could be precip- 

 itated by alcohol, and it was found to represent about 80 per cent of the original starch. 

 Various other familiar oxidizing agents have been employed by different investigators, 

 especially permanganate of potassium. 



Permanganate of potassium was used by von Siemens and Witt (Jour. Soc. Chem. 

 Industry, 1896, xv, 36G). The starch is stirred in water and a saturated solution of per- 

 manganate is added until the pink color of the latter in the liquid persists. Manganese 

 peroxide is deposited in state of extreme di\-ision on the grains, which assume a brown color. 

 The starch is well washed, treated with a dilute solution of hydrochloric acid of a 0.5 

 per cent strength upward, according to the nature of the starch, then treated with alkali, 

 and as soon as it gives a perfectly clear solution it is filtered off and freed from the manga- 

 nese salt by sulphurous acid or bisulphite, then washed and dried. 



A number of oxidizing agents, including bleaching powder, chloric acid, magnesium 

 dioxide, chromic acid, and potassium permanganate were used by Schmerber (Bull. Soc. 

 Ind. Mulhouse, 1896, 238) to hquefy starch, but the last substance was found to give 

 the best results. Equal quantities of starch and water are mixed thoroughly until the 

 starch is in suspension, to which is then added one-fiftieth of the weight of starch of a 

 warm 40 per cent solution of permanganate. The mixture becomes at first a reddish violet, 

 turning to a dark brown. After 24 hours, to a solution consisting of about one-twentieth 

 the weight of starch there is added hydrochloric acid in 5 volumes of water at intervals 

 during constant stirring until the starch is decolorized, after which the starch is washed 

 repeatedly to remove the acid and manganous chloride, and dried. The starch thus pre- 

 pared yields a solution that is limpid and transparent. On standing the solution becomes 

 cloudy, which cloudiness disappears upon heating. Schmerber's results were confirmed by 

 Dollfus and Scheurer (Bull. Soc. Ind. Mulhouse, 1896, 241). 



Fernbach and Wolff (Seventh Internat. Congress Appl. Chem., London, 1909) liquefied 

 starch to the limpidity of water in 15 minutes by subjecting a 5 per cent starcli-paste with 

 a few drops of hydi-ogen peroxide and anmionia at a temperature of 70° to 75°. To each 

 5 c.c. of paste was added an amount of hydrogen peroxide equal to 0.005 gram of oxygen, 

 and 0.004 gram of ammonia, but an excess of alkali was not found to be harmful, and it 

 noted that other alkaUs may be substituted. Weak acidity retarded liquefaction. Other 

 hquefying substances were studied, especially the sulphates of iron and copper. In the 

 liquefaction in the presence of ammonia some product in very small quantity is formed 

 which partially neutralizes the ammonia. With a relatively large amount of hydrogen 

 peroxide together with ferrous sulphate and sodium hydroxide the quantity of um-educed 

 starch was very small, while with hydrogen peroxide alone a large quantity of unreduced 

 starch remains. By subjecting 25 c.c. of the paste with 0.001 gram of ferrous sulphate, 

 0.042 gram of oxygen in the form of hydrogen peroxide, and O.OOOG gram of sodium hydrox- 

 ide for 2 hours at a temperature of 75° to 78°, the preparation no longer gave a color reaction 

 with iodine, and it had acquired an acid reaction and a high reducing power. The product 



