140 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



Jaquclain in 1S40 (loc. cit.) recorded that when starch is subjected to a temperature of 

 1G0 it is converted in part into dextrin and glucose. This statement was confirmed or 

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

 Jahr. u. d. Fort. d. Tliierchemie, 1881, xi, 80) was led to repeat the experiments to deter- 

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

 kind and quantity of starch at 149 yielded a larger amount of sugar the less the cjuantity 

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

 substance whose power is lessened by dilution. He also noted that hy 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 alkalme 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. u. d. Fort. d. Tliierchemie, 

 1881, XI, 86) does not agree with Sachsse's statement regarding the formula for starch and 

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

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

 trose, according to the ecjuation a;(CoHio05)-|-H20 = CoHi20(3, the yield of glucose should 

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

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

 acid according to tlie method of Sachsse, and obtained 111.16 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 CgHioOs, the percentages found by other investigators in acid hydrolysis were 

 lower by Brunner 107, de Saussure 110, and von Allihn only 106 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 

 quantity with potato starch, he recorded only 106.8 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 Iiis belief that there is only one kind of 

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

 formed by the action of sulphuric, oxaUc, 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 formula of starch, the per cent of glucose, 

 and of glucose being the sole sugar i)roduct. Schulze dried wheat starch and saccharified 

 it by dilute hydrocliloric acid, and obtained by von AUilin's method (copper reduction) 

 110.986 of glucose per 100 of starch, corresponding almiost exactly to the formula CgHjoOs. 

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

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

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

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



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

 gated by von Allihn (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 2}/^ hours. Table 11 is a statement of his results. 



