SimMARY OF THE MORE IMPORTANT LfTERATURE TTP TO 1872. 91 



Delffs (Ann. d. Physik. u. Cheniie, ISGO, cix, G4S) confirmed Jessen's statement of 

 the solubility of crushed starch-grains. He also notes that while the soluble constitutent 

 of starch has been looked upon as a form of dextrin, its various reactions show that it does 

 not correspond with the three dextrins described by Mulder {Joe. cil.), and therefore that 

 it must be another form of dextrin if it is to be classed as a body of this kind. He associated 

 this substance with a hyj^othetical isomer from which the starch-substance is supposed 

 to be formed, and to wliich he gave the name amylogen. 



Knop (Chem. Centralblatt, 1860 v, 367) also found that crushed raw starch is soluble 

 in water, but he thought that sufficient heat was formed during the pulverization to gel- 

 atinize the grains, and thus cause solution. This assumption, however, was subsequently 

 disproved by Jessen (see page 92). 



Musculus (Ann. dechim. et phys., 1860, LX, 203; Compt. rend., 1861, liv, 194) reported 

 that diastase, and also dilute sulphuric acid, changes starch into 2 parts of dextrin and 

 1 part of sugar, and that the acid may exert a slow but continuous action on the dextrin, 

 so that ultimately the preparation does not yield a color reaction with iodine. Wlien fresh 

 starch-paste was added the reaction was renewed, and it continued until there occurred a 

 loss of color response to iodine; but even at the end of the reaction there was much dextrin 

 remaining, there being present always at this time 2 parts of dextrin to 1 part of sugar. 

 In his later contributions (page 94) he gives equal proportions of dextrin and sugar when 

 the reaction becomes stationary. He thought that the accumulation of sugar prevented 

 further changes of dextrin, but not of starch ; and he believed the starch is not converted into 

 dextrin, and dextrin into sugar, but that by a process closely associated with an absorption 

 of water the molecules of starch were split into dextrin and sugar. The theory of this 

 splitting was founded on the fact of the production of these two products in definite ratio. 



The work of IV'Iusculus received support in the investigations of Payen (Compt. rend., 



1861, Liii, 217), who recorded that the resulting sugar prevents a further production of 

 sugar, and that by removing the sugar starch may be converted into dextrin and sugar 

 in almost any quantity, but never only into dextrin. Payen, howevei", opposed the view 

 of Musculus of the splitting of starch into dextrin and sugar. 



The disappearance upon heating of the blue coloration of a starch-solution treated 

 with iodine was reported by Diu-oy (Compt. rend., 1860, li, 1031). Baudrimont (Compt. 

 rend., 1860, li, 825), in seeking the cause of the loss of the color of the iodide of starch 

 on heating, concluded that it is o\\ing to the evaporation of the iodine, the vapor resting 

 on the liquid, and the color returning upon cooling owing to accompanying resolution 

 of the iodine. Pohl (Jour. f. prakt. Chemie, 1861, lxxxiii, 35) offered a different expla- 

 nation, and holds that hot water has a greater affinity than starch for iodine, whereas 

 with cold water the reverse is true. Schonbein (Jour. f. prakt. Chemie, 1861, lxxxiv, 

 402) states that Baudrimont's explanation is untenable, and that Pohl's is correct; that 

 iodide of starch is a chemical compound; and that there is no such thing as a colorless 

 iodide of starch. Schonbein's view was supported by Fresenius (Zeit. f. analyt. Chemie, 



1862, I, 84), Kraut (Gmelin's Lehrbuch d. organ. Chemie, 1862, iv, 554), and Kemper 

 (Archiv d. Pharm., 1863, cxv, 252). Pellet (Zeit. f. Chem., 1866, x, 352), however, asserted 

 that starch-iodide is insoluble in cold water and that it loses its blue color upon heating 

 because it is soluble in hot water and loses its color when it goes into solution. 



The oft-repeated observation of the solubihty of pulverized raw starch in cold water 

 was confirmed by Fliickiger (Zeit. f. Chemie, 1861, iv, 104), who also noted that the solu- 

 bility was increased in the presence of potassium chloride. During the same year, Nossian 

 (Jour. f. prakt. Chemie, 1861, lxxxiii, 41) examined the hygroscopic properties of starch 

 (Chapter IV, page 167); and Lippmann (Jour. f. prakt. Chemie, 1861, lxxxiii, 51) reported 

 the results of his experiments on the temperature of gelatinization of different starches 

 (Chapter IV, page 175). 



