154 



REACTION-INTENSITIES OF STARCHES. 



The independence of the variations in the courses of 

 these two curves, together with the individuality of the 

 salicylate curve when compared with curves of the reac- 

 tions of the other reagents, suggests peculiar relation- 

 ships of the salicylate with the starch molecule that are 

 worthy of special study. While this reagent is, at least 

 in the concentration used, of comparatively little value 

 in the differentiation of genera, it is not only of marked 

 usefulness in recognition of subgeneric groups, as stated, 

 but also in the differentiation of species and hybrids (see 

 Chart A 18, page 183) ; and it has proven of much value 

 in the study of the qualitative reactions of different 

 starches, as will be found by reference to data in Part II 

 and to Tables G 1 to C 17 in subsequent pages. Lens 

 (Seventh Inter. Congress Applied Chem., London, 1909; 

 Jour. Soc. Chem. Ind., 1909, xxvii, 731) had already 

 found that this reagent could be used in the microchemi- 

 cal differentiation of starches from different sources. 

 He states that if a trace of rye starch, in a hanging drop 

 of a solution of 1 part of sodium salicylate in 11 parts 

 of water, is examined under a magnification of 200, at 

 the ordinary temperature, it will be found that after the 

 lapse of an hour (more distinctly after 24 hours) most 

 of the large granules have swollen and that only a small 

 part resists the action of the salicylate and still shows the 

 polarization cross between crossed nicols. In the case 

 of wheat starch, only a few of the large granules become 

 swollen ; after 1 to 24 hours the outline of the imswoUen 

 wheat starch-granules is sharply defined, and the gran- 

 ules, imlike those of rye starch, do not become flattened 

 (starch of any kind which has been altered by storage in a 

 moist condition swells on treatment with the salicylate 

 solution). Barley and millet starches swell to a small 

 extent only. Only few of the grains of oat, maize, rice, 

 potato, bean, pea, lentil, and arrowroot starches become 

 swollen. 



The calcium-nitrate and strontium-nitrate curves 

 (Chart B 37) exhibit wide excursions, those of the latter 

 being the more marked; and the fluctuations tend with 

 few exceptions to correspond in their directions, although 

 with more or less marked quantitative variations. Both 

 generic and subgeneric differentiations are as conspicuous 

 as in the preceding charts; but inversion of the curves 

 does not occur at any point. The reactions of these 

 reagents are the same or practically the same in Amaryllis 

 belladonna, Hwmanthus kaiherinw, Crinum zeylanicum, 

 Lilium chalcedonicum, L. pardalinum, and Begonia sin- 

 gle crimson scarlet; and very nearly the same in Hippeas- 

 trum titan, L. mwrtagon, and L. tenuifolium. Else- 

 where the differences range within variable limits, the 

 widest being in Brunsvigia josephinw, Crinum moorei, 

 C. longifolium, Nerine crispa, N. bowdeni, N. sarrUensis 

 var. corusca major, and Begonia socotrana. 



The curves of the uranium-nitrate and cobalt-nitrate 

 reactions (Chart B 38) bear in general close relationships 

 to the curves of the preceding chart, the most noticeable 

 differences being apparent in the generally higher reac- 

 tivities of calcium nitrate and strontium nitrate, par- 

 ticularly the latter. The curves tend to be distinctly 

 closer than with the latter reagents ; no inversion of the 

 curves occurs at any place; and generic and subgeneric 

 differentiations, especially the latter, are with rare excep- 

 tions well marked. 



The copper-nitrate and cupric-chloride curves (Chart 

 B 39) are very similar to those of the two preceding 

 charts, the reactions tending to be the same or somewhat 

 greater than with uranium and cobalt nitrate, but as a 

 whole distinctly lower than with calcium nitrate and 

 strontium nitrate. Both generic and subgeneric dis- 

 tinctions are well marked. 



Barium chloride and mercuric chloride in the con- 

 centrations used are the weakest of all of the reagents in 

 the gelation of starch. Both curves (Chart B40) are 

 therefore lower, as a whole, than is found in the other 

 charts, the barium-chloride curve being distinctly the 

 lowest curve recorded. The fluctuations in this chart 

 are in close correspondence with those, of the imme- 

 diately preceding charts. No inversion of the curves 

 occurs except possibly in Hamantlius puniceus, where 

 the difference in the reactions falls within the limits of 

 error of experiment. 



Eeviewing these charts, as a whole, from both general 

 and special aspects, it will be found that they may be 

 divided primarily into two well-defined groups in accord- 

 ance with the peculiarities of the curves: first, those 

 showing the reactions with polarization, gentian violet, 

 safranin, and iodine; second, those showing reactions 

 with temperature and chemical reagents. This distinc- 

 tion is due in part to differences in the method of cali- 

 brating reaction-values and (in part and chiefly) to 

 differences in the inherent characters of the reactions. 

 As before noted, and of fundamental importance at this 

 juncture, the scale-values in the experiments with polar- 

 ization, gentian violet, safranin, iodine, and temperature 

 are different from those in the chemical reagent experi- 

 ments ; the polarization reaction is an optic phenomenon 

 that is without associated molecular disturbance; the 

 gentian-violet and safranin reactions are probably sim- 

 ple phenomena of adsorption, but without apparent 

 molecxilar disturbance; the iodine reaction is probably 

 a manifestation of chemical combination of the iodine 

 with the starch to form a feeble union, but without 

 a detectable appearance of intermolecular disorganiza- 

 tion; the temperature reaction elicits an intermolecular 

 disaggregation that is associated with hydration; and 

 the chemical-reagent reactions are expressions of not only 

 intermolecular breaking down and hydration, but also 

 various quantitative and qualitative modifications in the 

 starch molecules and their derivatives that depend upon 

 differences in concentration and components of the rea- 

 gents, the starch molecule because of its amphoteric 

 properties combining with both acids and bases, and the 

 gelatinization processes being more or less modified by 

 some reagents by associated chemical changes. The 

 polarization curve (Chart B 1) bears no well-defined 

 relationship, except of an apparently accidental charac- 

 ter, to any of the other curves. The gentian-violet and 

 safranin curves (Chart B 2) are very much alike, and 

 where differences are noted they are doubtless to be 

 attributed to errors of experiment; and these curves 

 stand apart from all other curves. The iodine and tem- 

 perature curves (Chart 3) show in general a closeness 

 which suggests that since in the temperature reaction 

 there is intermolecular disorganization there is a more 

 marked molecular change in the iodine reaction than is 

 shown by the microscope in ordinary or polarized light. 



