BBACTION-INTENSITIES WITH EACH AGENT AND REAGENT. 



147 



of two different kinds of group*. Th-- starch molecule 

 U-haves a.i an ami !ectrolyte, . timr M an acid 



or hn.e in n-lation to tli-- components of the reagents 



rm different salts, the reactions bring ' 

 the splitting off of hydrogen or hydrxyl iona. All <>f 

 the reagents used In thil research to gelatinize starch 

 are aqueous solution* of electrolytes or imperfect electro- 

 lytes, am! hence each is partially ionized, the degree of 

 ation varying with the different reagent* ; more- 

 i \ariety of elementa and molecules, acid 

 and hase. that may enter into chemical oomliination with 

 the starch molecules. llcmv it fnllnwa that each solu- 

 tion ii a complex that consist* of molecules of wmter and 

 solute, and of inns of water and of solute. Having now 

 a starch molecule that mav assume either acid or basic 

 rties, and reagents that contain both water and 

 of elements and moleriili-s that may enter 

 hemical combination with the starch to form gaits. 

 that the phenomena of gelatinization or 

 swelling, quantitatively and qualitatively, may Tary more 

 or le. markedly in accordance with the chemical reac- 

 tion* that occur coincidentlv with the adsorption of 

 water. An examination of the list of reagents used in 

 search will show that there arc well-defined classi- 

 fications or groupings in accordance with peculiarities 

 of the substances entering into the reagents as the 

 solnt. r in-itam-c. organic acid, inorganic acids, 



potassium salts, sodium salts, hydroxides, sulphides, ni- 

 trates, chlorides, etc. Not only are variations to be 

 expected in the reactions because of differences in the 

 composition of these reagents, but also because of differ- 

 ences in the molecular arrangements of the starch mole- 

 If the starches from different plant sources exist 

 in different stcreoisomcric forms, it seems upon the basis 

 of our knowledge of the peculiarities of stereoisomers 

 in general that variations in the reactions that are due 

 to this peculiarity may be as great or even greater than 

 those due to differences in the reagents that is, that 

 variation* in the reactions of different starches with a 

 given reatrcnt may be as marked or more marked than 

 those in the case of a single starch with different rea- 

 gents. This has been found to be a fact by the results 

 of this research. 



In the study of the phenomena of gelatinization that 

 are definitely associated with peculiarities of the rea- 

 gents the object has been to demonstrate differences in 

 the behavior of different reagents without reference to 

 the cause of these differences, except as they go to prove 

 xistence of starch in stereoisomeric forms that are 

 modified in specific relationship to the plant source. 

 Obviously, there would be many advantages in a com- 

 bined study of both gross phenomena of gelatinization 

 and reactions that occur during and subsequent to gela- 

 tinization, and much is to be gained by the use of reagents 

 in equimolecular solutions ; but certain unavoidable con- 

 ditions attending this research made it necessary to 

 pursue the studies of the actions of reagents with refer- 

 ence to effect and without more than incidental reference 

 to cause. 



It will be recognized, from what has been stated, that 

 the reactions are conditioned by both starch and rea- 

 gent. Having a number of starches of presumably dif- 

 ferent stereoisomeric forms, there remained the selection 



of the kind and concentration of reagents that would 

 < IK it nut -h differences in the reactions as would demon - 

 -tratc clearly not only isomerism but an isomerism that 

 is specific in relation to genera, species, varieties and 

 hybrids. It was found advantageous, in formulating 

 these solutions, to disregard entirely concentrations upon 

 the gram-molecular basis and to determine experimen- 

 tally the strengths of solution that seemed best adapted 

 to gire wide ranges of reaction with different stc- 

 under the same conditions of experiment. The marked 

 variations in the behavior of different starches with a 

 given reagent, and of different reagents with a given 

 starch, are presented in striking form in Charts A 1 

 to A 26; but these features are brought out even better 

 in certain respects in Charts E 1 to E 46, and very much 

 better in ninsf respects in Charts B 1 to II I'.'. The fir-t 

 group of charts has been considered in a previous sub- 

 section of this chapter; the second group will be taken 

 up in a subsequent subsection ; and the third group will 

 here be studied in only sufficient detail to meet 

 requirements. 



In the construction of the group of charts designated 

 B t to B 42 the main purpose was to bring out certain 

 extraordinary peculiarities in the reactions of selected 

 pairs (occasionally more) of reagents with a number 

 of starches which are taken tentatively to be representa- 

 tive of genera and of suhgenerie divisions. Tn the selec- 

 tion of the reagents for comparison it seemed that 

 characteristics peculiar to each of the several reagents 

 could be presented particularly well if in one group of 

 this series of charts the reactions of a given reagent are 

 taken as the standard of comparison with the react ions 

 of each of the other 25 agents and reagents; and if in 

 a second group we compare the reactions of certain two 

 or more agents or reagents, selected because of certain 

 peculiarities, such as similarity or dissimilarity of agent 

 and reagent, this plan was carried out. Tn th^ first 

 series the reactions of nitric acid are taken as the stand- 

 ard; and in the second series the reactions of anilines, 

 inorganic acids, hydroxides, sulphides, etc., various com- 

 binations of two or more agents and reagents were. made. 



To reiterate, there is in the polarization reactions 

 no molecular alteration of the starch molecule; color 

 reactions are present with gentian violet and safranin 

 which are attributable ti adsorption without detectable 

 attendant molecular disorganization ; in the iodine reac- 

 tions there is in all probability a union of iodine and 

 starch to form an unstable iodide of starch, but no 

 intermolecular breaking down ; in the temperature reac- 

 tions intermolecular disorganization is associated with 

 the adsorption of water, but without the loss of properties 

 that characterize the starch molecule; and in the chemi- 

 cal-reagent reactions not only intermolecular disorgan- 

 ization occurs, but various associated reactions that 

 depend upon the acid or base character and parti- ul T 

 elements and molecules of the reagents. From this it 

 would follow that these reactions fall into well-defined 

 groups: the polarization, aniline, iodine, temperature, 

 and chemical-reagent reactions, respectively. 



When the reaction-intensities with polarization, gen- 

 tian violet, safranin. iodine, and temperature are plotted 

 out in curves, as in Chart B 1, and the chemical-reagent 

 reaction-intensities are plotted out, as in Charts B 2 to 



