152 



REACTION-INTENSITIES OF STARCHES. 



as those of different genera, represent probably the most 

 remarkable feature of the chart, and they might natur- 

 ally be regarded as being accidental were it not that 

 corresponding peculiarities have been recorded in nearly 

 all instances where the reactivities of two agents or 

 reagents have been compared. A further consideration 

 of this striking phenomenon will be taken up later. 



The inorganic acids, here typified by nitric acid, sul- 

 phuric acid, and hydrochloric acid (Chart B 32) are of 

 pecular interest because of their pre-eminently hydrionic 

 character, and because in each, in accordance with ionic 

 action in relation to the swelling of proteins, the active 

 agent in bringing about the alteration in surface tension 

 that initiates gelatinization is the anion. But that these 

 ions alone are insufficient to account for differences in 

 the phenomena of gelatinization due to these agents, that 

 the cations in each acid play a part, and that the reac- 

 tions are modified by both concentration and kind of 

 ions, is rendered apparent by a study of the curves. The 

 most conspicuous features of this chart are: The wide 

 differences exhibited by the different kinds of starch, 

 and the obvious generic and subgeneric groupings; the 

 identity or practical identity of the reactions of two or all 

 three of the acids with certain starches in contrast with 

 the marked to very marked variations with others ; and 

 the tendency generally for the nitric-acid and the hydro- 

 chloric-acid curves to run closely together and, as a rule, 

 well apart from the sulphuric-acid curve, with, however, 

 occasional greater closeness of the hydrochloric and sul- 

 phuric-acid curves than of the nitric-acid and hydro- 

 chloric-acid curves. This separation of the curves, while 

 in part unquestionably due to differences in concentra- 

 tion of the reagents, is also partly due to differences in 

 the characters of the reactions dependent upon the ca- 

 tions. In Amaryllis and Brunsvigia all three reagents 

 yield exceedingly rapid reactions, but in Brunsvigia 

 the nitric-acid reaction is distinctly less rapid than the 

 sulphuric-acid and hydrochloric-acid reactions, the last 

 two being the same. In Crinum moorei, LUium mar- 

 tagon, L. tenuifolium, L. chalcedonicum, L. pardalinum, 

 and Begonia single crimson scarlet the reactions with all 

 three reagents are very rapid, and are the same or prac- 

 tically the same. The sulphuric-acid and hydrochloric- 

 acid reactions are nearly the same or practically the 

 same in Brunsvigia josephince, Crinum longifolium, Iris 

 persica var. purpurea, Phaius grandifolius, and MUtonia 

 bleuana. The nitric-acid and hydrochloric-acid reac- 

 tions tend to be close to very close, and at the same time 

 well separated from the sulphuric-acid reactions, in Hip- 

 peastrum titan, H. ossultan, H. dceones, Hcemanthus 

 katherina, Crinum zeylanicum. Iris iberica, I. trojana, 

 and 7. cengialti; to be approximately mid-intermediate in 

 Hcemanthus puniceus, Nerine crispa, N. bowdeni, N. 

 sarniensis var. corusca major, Narcissus tazetta grand 

 monarque, Gladiolus Tristis, and Tritonia pottsii. 



Curiously, in only 1 of the 28 starches (Begonia soco- 

 trana) is the hydrochloric reaction lower than the reac- 

 tions of the other two acids ; and not only is the difference 

 in the reaction-intensities very marked between this and 

 the next closer or nitric-acid reaction, but the difference 

 between the latter and the sulphuric-acid reaction is also 

 very marked ; and the three reactions form a group that 

 is widely and remarkably different from the reactions 



observed in the other Begonias. It is of especial interest 

 to note that in Hcemanthus, Crinum, and Iris, among 

 which there are subgeneric representatives, the sub- 

 generic differentiation is in each genus well marked. 

 These extraordinary variations in the relations of the 

 reactions of the three reagents are inexplicable upon the 

 basis merely of differences in ionic and molecular con- 

 centration of the reagents; or upon differences in the 

 starches that may be assumed to be due to varying pro- 

 portions of components of a mechanical mixture ; or 

 upon differences in reaction owing to the amount or kind 

 of impurities; but they are entirely explicable upon the 

 basis of different stereoisomeric forms of starch that 

 have specific and varying relationships to the kinds and 

 concentrations of solutes in aqueous solution. 



The potassium-hydroxide and sodium-hydroxide chart 

 (Chart B33) presents features which, while less ex- 

 traordinary, are quite interesting and significant. These 

 reagents, like the acids, bear very close relationships, 

 but there are aqueous solutions that are pre-eminently 

 cationic, and here, as in the acid chart, it will be seen 

 that reaction-intensities vary within the extremes of the 

 abscissae and elicit very definitely but in modified forms 

 the generic and subgeneric divisions that are brought 

 out so strikingly by the acids. Moreover, it is perfectly 

 obvious that here, as in preceding charts, while certain 

 differences may justifiably be attributed to differences 

 in the concentration of the reagents, other differences 

 seem to be inseparable from the presence of stereoiso- 

 mers and of components of the solute that form specific 

 and variable kinds of products through chemical union 

 with the raw-starch molecules and their derivatives. 

 The concentration of the potassium-hydroxide solution 

 is 1.5 grams to 110 c.c. of water, and of the sodium- 

 hydroxide solution 0.5 gram to 100 c.c. of water. It will 

 be seen that the curves tend for the most part to keep 

 close together in their variations; that while generally 

 the potassium-hydroxide curve is the higher it is in a 

 number of instances somewhat or even markedly lower, 

 and in other instances the same or practically the same 

 as the sodium-hydroxide curve ; and that the generic and 

 subgeneric divisions that were demonstrated in the pre- 

 ceding charts are here also elicited but in modified forms. 

 The two reactions are the same or practically the same 

 in Hcemanthus katherinw, Crinum zeylanicum, Lilium 

 martagon, L. tenuifolium, L. chalcedonicum, L. parda- 

 linum, Iris trojana, and Begonia single crimson scarlet. 

 The potassium-hydroxide reactions are higher in all of 

 the remaining starches excepting Crinum longifolium, 

 Narcissus tazelta grand monarque, Iris iberica, I. cen- 

 gialti, I. persica var. purpurea, Gladiolus tristis, and 

 Tritonia pottsii, in which group it is markedly to very 

 markedly lower, chiefly the latter. The very mnrkcd 

 differences in the reaction-intensities of the two rea- 

 gents in Nerine and Begonia in comparison with the dif- 

 ferences generally stand out very conspicuously. 



One feature of especial interest is to be noted in the 

 species of Crinum: C. moorei is more sensitive to potas- 

 sium hydroxide than to sodium hydroxide; C. longifo- 

 lium shows the reverse; and C. zeylanicum about equal 

 reactivity with the two reagents. Another feature is to 

 be found in species of Iris, the first three showing with 

 sodium hydroxide the same sensitivity and the last a 



