PHENOMENA OF DIGESTIBILITY — BOILED STARCHES. 



193 



made up to 500 c.c. To each 70 c.c. of each starch-sokition was added 1 c.c. of malt extract 

 at 40°, and the preparation kept at 40° for 1 hour. The preparation was then boiled 

 and made up to 100 c.c. The results in all cases, corrected for reduction of starch-solutions 

 and malt e.xtract, are shown in table 25. 



T.\BLE 25. 



Table 26. 



It is evident, as Ford states, that the origin of the starch has, under these conditions, 

 no influence on the results when the starches are equally purified. From the same starches 

 soluble starches were prepared according to Lintner's method, and similarly tested, with 

 the results shown in table 26. 



The specimen designated potato I was made from a "purest commercial farina" by 

 gclatinization and subsequent liquefaction with a trace of diastase. The solution after con- 

 centration was precipitated and washed with tap-water and twice with alcohol. The result, 

 Ford states, shows well how impurities cling to the starch. The slight differences shown in 

 the table, he holds, may be accounted for by variations in the impurities, and one may safely 

 infer that equally purified preparations of Lintner's soluble starch from starches of different 

 origin will give the same maltose production with equal quantities of diastase. The above 

 preparations, though exhaustively washed with distilled water, were by no means pure. 



Further studies of the quantitative identity of the decomposition products of starches 

 of various origins were made by Ford and Guthrie (Joiu-. Soc. Chem. Ind., 1905, xxiv, 

 605). The starches were prepared by these investigators, with the exception of arrowroots, 

 which were bought and then subjected to purification in the usual manner. All of the 

 starches were purified by treatment with 0.2 per cent caustic soda and hydrochloric acid, 

 washed with distilled water, and extracted with alcohol and ether when necessary; then 

 air-dried and further dried at 25° to 30°. In each experiment 5 grams of starch were gela- 

 tinized as usual, cooled to 05°, and converted during VA hom's with 25 c.c. of malt extract 

 that had previously been heated for 10 to 15 minutes at 65°. The converted preparations 

 were made up to definite volumes and the specific gravity, optical rotation, and copper- 

 reducing power were observed. Their experience convinced them of the validity of "the 

 law of relationsliip " pronounced by Brown, Morris, and Millar (Jour. Chem. Soc, 1897, 

 Lxxi, 115) ; hence, determinations of the solids and their optical rotation is all that is neces- 

 sary. The following rotatory values were recorded (table 27) : 



Table 27. 



Kind of starch. 



Potato (controls of same 

 specimen) 



Pea 



Barley 



Wheat 



Oats 



13 



(a) 



i'a.»3 



161.0 



160.7 

 159.5 

 160.7 

 161.0 

 160.8 

 161.0 

 162.0 



Kind of starch. 



Corn 



Tous-les-mois (Cannaedulis) 



Arrowroot (Maranta) 



Rice 



Lentil 



Banana 



Barley, malted 



Barley, malted 



(a)r 



160.0 

 159.7 

 161.0 

 161.5 

 160.0 

 159.7 

 160.7 

 160.8 



Kind of starch. 



Potato (commercial) 

 Potato (purified). . . . 



Rye 



Buckwheat 



Chestnut 



Pari 



Millet 



Me 



163.4 

 161.0 

 163.2 

 164.0 

 166.9 

 163.7 

 162.6 



