REACTION-INTENSITIES WITH EACH AGENT AND REAGENT. 



155 



Inasmuch as the temperature valuations are quite 

 exact (as exact as the determinations of the melting- 

 points of crystalline substances), and as the iodine valua- 

 tions are of a gross character, it seems probable that 

 seeming deviations from what is judged to be the normal 

 in the two charts may be due to errors of experiment; 

 but some of these differences are explicable only upon 

 the assumption of peculiarities of the molecules of the 

 different starches, causing them to behave differently 

 with different reagents, as was found in the study of 

 the reactions with the chemical reagents. The tempera- 

 ture curve, while very much more limited in its excur- 

 sions than the curves of most of the chemical reagents, 

 bears in general a well-defined relationship in its fluc- 

 tuations to the variations collectively of the latter. This 

 relationship becomes more obvious when the temperature 

 values are iu a modified form to render them more con- 

 sistent with the chemical reagent values, as shown in 

 Chart B 6, in which the temperature and nitric-acid 

 curves are figured, the former being exhibited in, one 

 curve in accord with the standard calibration and in 

 another with a modified valuation so formulated that 

 these values, like the chemical reagent values, extend 

 over the entire limits of chart between the highest and 

 lowest abscissae. When, however, the iodine values are 

 similarly modified (Chart B 8) there is no more similar- 

 ity, on the whole, between this modified form of curve 

 and the nitric-acid curve than there is when the standard 

 calibration is used — in fact, if anything, there is a 

 greater lack of correspondence. Comparisons of this 

 modified curve with curves of the reactions of other 

 reagents are fully confirmative of these findings in sup- 

 port of inherent differences in the behavior of the starch 

 molecules in these reactions. In a word, these facts 

 indicate quite convincingly that the iodine, temperature, 

 and nitric-acid reactions are in some way or ways funda- 

 mentally different and that there is an obscure rela- 

 tionship between the temperature and nitric-acid curves 

 that does not exist between the iodine and nitric-acid 

 curves. In these comparisons the nitric-acid curve has 

 been taken as a prototype of the chemical-reagent curves. 

 When the latter are individually compared with this 

 prototype and with each other it will be found that, while 

 no two are alike, all conform to this type in a manner 

 that is comparable to the conformity of the members of 

 a genus to a generic prototype. In other words, the 

 variations shown by the different reagents are comparable 

 to the variations exhibited by the members of a genus. 

 Sufficient reference has doubtless been made to the 

 peculiarities of the reactions of the various reagents, 

 individually and in couples, that are specific to each 

 reagent in association with peculiarities of the various 

 stereoisomeric forms of starch, yet it seems that addi- 

 tional statements may be made with profit in respect 

 especially to certain reactions of well-defined natural 

 groups of reagents, such as the inorganic acids, hydrox- 

 ides, sulphides, nitrates, chlorides, potassium salts, so- 

 dium salts, copper salts, etc. The only organic acid used 

 in this research is pyrogallic acid, to the solution of 

 which was added a small amount of oxalic acid for the 

 purpose of preservation. Chromic acid, while belonging 

 to the inorganic group that comprises nitric, sulphuric, 

 and hydrochloric acids, may for certain reasons be con- 



sidered with pyrogallic acid, and then with the other 

 three acids. Chromic acid acts on the starch grain in 

 a manner that is not only entirely individual and distinc- 

 tive in comparison with the actions of the other acids, 

 but also quite different from that of any other reagent. 

 This acid causes the grain at first to be altered into a 

 gelatinized capsule and a semi-liquid contents ; the cap- 

 sule then ruptures at some point and the contents flow 

 out; and then both capsular part and escaped contents 

 pass rapidly into solution. PyrogaUic acid brings about 

 changes that belong to a fundamental type that is com- 

 mon to the other chemical reagents, but variously modifi- 

 able with each reagent. By comparing the chromic-acid 

 and pyrogallic-acid curves (Chart B 31), and then these 

 with the nitric-acid, sulphuric-acid, and hydrochloric- 

 acid curves (Chart B'33), it will be seen that the first 

 two differ markedly from each other, that the chromic- 

 acid curve is not in closer relationship than the pyro- 

 gallic-acid curve to the curves of the group of inorganic 

 acids, and that the pyrogallic-acid curve is more closely 

 related than the sulphuric-acid curve to the nitric-acid 

 and hydrochloric-acid curves. " The sulphuric-acid curve 

 in comparison with the nitric- and hydrochloric-acid 

 curves appears to be vagrant, but this seeming discrep- 

 ancy may be due, in a large measure at least, to the 

 higher reactive-intensity of this reagent. 



These five reagents undoubtedly have, because of their 

 inherent chemical differences, different chemical relation- 

 ships to the starch molecule and accordingly yield reac- 

 tions that can not be identical qualitatively. Chromic 

 acid and nitric acid apparently stand apart from the 

 other acids because of their oxidizing properties, but it 

 may be, as suggested by the investigations of Sacharow 

 and of Griiss (see previous memoir, pages 95, 146, and 

 186), that oxygen is essential in both the initial and final 

 stages of the saccharification of starch. If this is so, 

 the part played by oxygen in the actions of the other 

 reagents is masked. However, chromic acid has been 

 used commercially to liquefy starch and form dextrin 

 and sugar because of its asserted oxidizing power. Nitric 

 acid has been found similarly valuable to form oxalic 

 acid from starch and other carbohydrates. Pyrogallic 

 acid, on the other hand, is an active deoxidizer, taking 

 up oxygen freely ; and, moreover, this acid does not, as is 

 well known, form true salts. Both sulphuric and hydro- 

 chloric acids have been employed by a large number of 

 investigators to reduce starch to dextrin and sugar (see 

 Publication K"o. 173, page 104) . While our knowledge of 

 the exact characters of the intermediate products of 

 saccharification is very limited, it is justifiable, from 

 what is known, to assume that the interactions of these 

 various reagents with the starch molecule may be quite 

 as varied as those which occur in the evolution of oxygen 

 from peroxides, chlorates, and permanganates, respec- 

 tively, and that they may differ even more than the proc- 

 esses of enzymes and aoids, respectively, in the liquefac- 

 tion, dextrinization, and saccharification of starch (see 

 previous memoir, page 149). 



Probably no two pairs of curves elicit more interest 

 than those of potassium and sodium hydroxides and nitric 

 and hydrochloric acids when the members of each pair 

 and of the two pairs are compared. The first two rea- 

 gents are pre-eminently cationic; the latter is pre-emi- 



