92 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



The actions of an amnioniacal solution of oxide of copper on various starches were studied 

 by Weiss and Weisuer (Sitzungsber. d. k. k. Acad. d. Wissenschaft z. Wein, 1862, xlvi, 311). 



The essential components of starch were recorded by Dragendorff (Jour. f. Land- 

 wirthsch., 1802, vii, 211) as follows: (1) True starch; (2) a radical base which remains 

 after starch has been heated to 60° in a concentrated solution of chloride of sodium con- 

 taining 1 per cent of hydrochloric acid; (3) Schulze's amidulin (Delff 's amylogen) ; and 

 (4) occasionally some dextrin. 



Kabsch (Zeit. f. analyt. Chemie, 1863, ii, 216) studied the properties of starches in 

 relation to the polariscope, to gelatinization, and to solubility. He noted that the polar- 

 iscopic appearances undergo change by the action of heat; that the grains, when exam- 

 ined in the polariscope with a quartz plate ground perpendicular to the axis, by turning 

 analyzer they behave like cellulose, being dextrogyrate or lavogjTate, according to con- 

 ditions; that the doubly refractive properties of animal and vegetable bodies are deter- 

 mined by a fixed, definite arrangement of the molecules, but that the arrangement is not 

 sufficiently uniform, as in ciystals, to speak of definite optic axes; that there are a large 

 number of substances which gelatinize or swell starch without dissolving it, the chief of 

 these agents being the eas]ly soluble haloid salts (but some salts prevent swelling, depend- 

 ing upon the concentration of the solution) ; that starch is completely soluble in glycerine 

 when heated for a sufficient length of time, and that the dissolved starch can be precipi- 

 tated from solution by alcohol, although the precipitate does not have the properties of 

 the original starch, the properties indicating a modification identical with Delff 's amylogen; 

 that starch is completely dissolved by the action of saliva and other ferments; that we 

 are justified in assuming that starch consists of two different substances, one of which, the 

 real starch-substance, is soluble in saliva (NageU and von MoM), in dilute acids (Melsens), 

 and in cold water after crushing (Reinsch, Jessen, Delffs, etc.) ; the other substance (cellu- 

 lose according to Nageli, and farinose according to von Mohl) is insoluble in the above- 

 mentioned media; that the outermost or densest layers, and especially the outermost, resist 

 all action of chemical agents longer than the less dense substances by wliich the lamellte 

 are surrounded and impregnated; and that the heat generated during the pulverization 

 of starch is a coagent in solution. 



Kemper (Archiv d. Pharin., 1863, cxv, 250) found that a weak solution of sugar- 

 free dextrin does not reduce Fehling's solution, but that a concentrated solution does. 



Nageli (Botanische Mittheil, 1863, 251; Sitzungsberichte d. k. k. Acad. d. Wissensch. 

 in Miinchen, 1862-1863) studied the reactions of iodine with starch-grains and cell-mem- 

 branes, the chemical composition of starch-granules and cell-membranes, and the chemical 

 difTerences of starch-grains. 



Jessen (Ann. d. Physik. u. Chemie, 1864, cxxii, 482) opposed the statement of Ivnop 

 and of Kabsch that heat has anything to do with the solubility of the comminutetl starch- 

 grains. Jessen found that the pulp showed a temperature of 20°, which is too low to have 

 any influence. 



The following year Payen (Ann. de chim. et phys., 1865, iv, 286) asserted that some of 

 the statements of Musculus pubUshed in 1860 are not correct. Payen found that diastase as 

 well as dilute acid will convert dextrin into sugar, and that of the entire product obtained 

 by the action of diastase on starch as much as from 17 to 50 per cent may consist of sugar. 



During the same year, Musculus (Ami. de chim. et phys., 1865, vi, 177) stutlied 

 the properties of what he terms true dextrin (acliroodextrin), and showed that this sub- 

 stance does not stain blue with iodine. 



A year later, Payen (Aim. de chim. et phys., 1866, vii, 382) repeated his experiments, 

 and he again gave evidence to disprove views of Musculus. He found that diastase as 

 well as sulphuric acid will produce varying proportions of sugar, and that sulphuric acid 

 when properly used produces SO per cent or more of sugar. 



