140 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



Jaqiiclain in 1S40 {loc. cit.) recorded that when starcli is subjected to a temperature of 

 100° it is con^'crtecl in i)art into dextrin and shicose. This statement was confirmed or 

 contradicted by different observers so that Soxhlet (Reportorium f. analyt. Chemie, 1881; 

 Jahr. ii. d. Fort. d. Thierchemie, 1881, xi, 86) was led to repeat the experiments to deter- 

 mine the cause of the disagreement. Soxhlet found by a preHminary test that a given 

 kind and quantity of starch at 149° 3'ieldcd a larger amount of sugar the less the quantity 

 of water present, from which he concluded that commercial starch contains a saccharifying 

 substance whose power is lessened by dilution. He also noted that by subjecting speci- 

 mens of the same starch for 5 hours at 149° entirely different proportions of sugar were 

 formed in accordance with the amount of acid present. Potato starch and wheat starch 

 showed acidity, 100 grams having an acidity equal to from 0.06 to 0.4 gram per 100 of 

 sulphuric acid; but rice and corn starch usually exhibit an alkaline reaction. He notes 

 also that even commercial starch has some reducing action, which may be due to the 

 presence of preformed sugar. 



Salomon (Reportorium f. analyt. Chemie, 1881; Jahr. ii. d. Fort. d. Thierchemie, 

 1881, XI, 80) does not agree with Sachsse's statement regarding the fornmla for starch and 

 the percentage of sugar obtainable (page 138). He found that the proportion of sugar 

 conforms best with the formula CoHjoOs for starch. In the conversion of starch into dex- 

 trose, according to the equation a;(C6Hio05)+H20 = C(3Hi20(i, the yield of glucose should 

 be 111.11 parts of dextrose to 100 parts of starch, whereas according to Nageli's formula 

 the amount would be 109.09. Salomon saccharified potato starch by boiling with dilute 

 acid according to the method of Sachsse, and obtained 111.10 and 111.11 per cent of 

 glucose. In other communications (Jour. f. prakt. Chemie, 1882, xxv, 348, and xxvi, 

 324) he notes that while he obtained the proportion required on the basis of the formula 

 being CqHioOs, the percentages found by other in\'estigators in acid hych'olysis were 

 lower — by Brunner 107, de Saussure 110, and von AllUin only 100 to 107. He reasons 

 that these differences may be due to incomplete desiccation of the starch or to faulty 

 methods in determining the quantities of sugar. Wliile he obtained the required theoretical 

 quantitj'^ with potato starch, he recorded only 100.8 per cent with rice starch, which differ- 

 ence he attributes to incomplete saccharification owing to an injurious effect of alkali 

 upon the starch during the process of preparation. Salomon (Jour. f. prakt. Chemie, 

 1883, xxviii, 82) in a later investigation asserts his belief that there is only one kind of 

 dextrin formed during saccharification of starch; and that glucose, but not maltose, is 

 formed bj^ the action of sulphuric, oxalic, citric, or tartaric acid, the conclusion as regards 

 sugar being based upon the determination of the specific gravity and rotatory and reducing 

 powers. 



The results of a study of wheat starch by Schulze (Jour. f. prakt. Chemie., 1883, xxviii, 

 311) support Salomon's conclusions regarding the fornuila of starch, the per cent of glucose, 

 and of glucose being the sole sugar product. Schulze tlried wheat starch and saccharified 

 it by dilute hydrochloric acid, and obtained by von AUihn's method (copper reduction) 

 110.986 of glucose per 100 of starch, corresponding almost exactly to the formula CgHioOs- 

 By the specific-gravity method he recorded 111.4; and by the polariscope method, 111.85. 

 By treatment with acetic acid imder pressure he obtained a dextrin corresponding to the 

 a-dextrin (erythrodextrin) of Bondonneau. Heating for 4 hours produced almost exclusively 

 this dextrin, but by continued heating the dextrin partially goes over into glucose. 



The maximum conversion of starch into sugar under varying conditions was investi- 

 gated by von AUihn (Zeit. d. Ver. f. d. Rubenzucker-Industrie, 1883, 786; Dingl. Polyt. 

 Jour., 1884, CCL, 554). Ten grams of anhydrous starch, containing 0.9 per cent of ash 

 and 0.3 per cent of insoluble residue, were subjected to 100 c.c. of dilute hydrochloric 

 acid of strengths varying from 1.33 to 10 per cent, and boiled for periods ranging from 2 

 minutes to 23^^ hours. Table 11 is a statement of his results. 



