144 



REACTION-INTENSITIES OF STARCHES. 



chart than in the sodium-sulphide chart. Iris is, 

 like Nerine, conspicuous by the differences of the 

 ordinates, but particularly in reversed ways. The 

 Iris ordinates in the potassium-sulphide chart are 

 distinctly longer than in the other chart and they are 

 of about the same length (the opposite to what is seen 

 in Nerine) ; and in the sodium-sulphide chart the ordi- 

 nates of three of the groups are the same, while those 

 of the fourth group are much shortened. More or less 

 marked differences in the two charts are seen in the 

 remaining generic groups, especially in members of 

 Begonia, Musa, and Miltonia. 



Another pair of reagents that yield reactions worthy 

 of especial examination are represented in Charts A 23 

 and A 24 (copper-nitrate and cupric-chloride reactions). 

 These two charts are in the corresponding groups 

 almost the same throughout, the chief differences being 

 noted in Crinum powellii, Lilium burbanhi. Iris sind- 

 jarensis, I. pursind. Begonia mrs. heal, Musa gilletii, 

 Miltonia (both parents and hybrid), and Gymhidium 

 eburneo-lowianum. These differences are in every case 

 such as not to fall within the limits of error of experiment. 



Any two or more of these charts can thus be com- 

 pared with the certainty of finding results that conform 

 to those referred to in the preceding pairs. 



The one feature above all others that serves to indi- 

 vidualize each chart is the variable relationships of the 

 reaction-intensities of the members of each of the differ- 

 ent sets of parents and hybrid and of groups of sets in 

 the different charts. For instance, taking the Amaryllis- 

 Brunsvigia set it will be seen upon comparing the dif- 

 ferent charts that differences in the average reaction- 

 intensities of this set in comparison with the differences 

 in other sets and groups of sets are nothing like so 

 striking and characteristic as are the differences in the 

 group itself in the various charts. In other words, while 

 there is a general tendency for the average reaction- 

 intensity of this group to rise or fall with the averages 

 of other groups in the different charts, the individual 

 members of the group exhibit marked independence in 

 the direction and extent of the changes. Thus, in this 

 group in the charts of chloral hydrate, pyrogallic acid, 

 potassium iodide, potassium sulphocyanate, sodium hy- 

 droxide, sodium salicylate, cobalt nitrate, copper nitrate, 

 cupric chloride, and mercuric chloride the four ordinates 

 are in couples, the parental couple being in the chloral- 

 hydrate reaction shorter than the hybrid couple, but in 

 the other reactions the reverse. In the reactions of 

 chromic acid, nitric acid, hydrochloric acid, potassium 

 hydroxide, sodium salicylate, and barium chloride all 

 four ordinates are the same or closely the same, there 

 being neither the coupling so obvious in the previous 

 set nor any marked departure of any from an average 

 standard. In the reactions of potassium sulphide, cal- 

 cium nitrate, strontium nitrate, and uranium nitrate 

 (with the exception of potassium sulphide and strontium 

 nitrate) no two of the four ordinates are alike with any 

 reagent, and the relative lengths of the four ordinates 

 vary in the different reactions, the order of length being : 



Potassium sulphide: Brunsvigia, Brunsdonna sanderw alba, 



Amaryllis, and Brunsdonna sanderoe. 

 Calcium nitrate: Brunsdonna sanderce alba, B. sanderw, 



Brunsvigia (these two being the same), and Amaryllis. 



Strontium nitrate: Brunsvigia, Brunsdonna sanderoe alba, 

 B. sanderce (these two being the same), AmMryllis. 



Uranium nitrate: Brunsdonna sanderce alba, Brunsdonna 

 sanderce, Brunsvigia, and Amaryllis. 



Such variations will be treated quite fully in the 

 following subsection: 



The Specificities of the Components of the 



Keagents. 



(Charts B 1 to B42.) 



Inasmuch as different starches behave differently, 

 qualitatively and quantitatively, with a given reagent, 

 and a given starch differently with different reagents, it 

 follows, as a corollary, that certain peculiarities of the 

 reactions are to be attached to the starches and certain 

 others to the reagents — in other words, the characters of 

 the reactions are conditioned, as before stated, by both 

 starch and reagent. In this research the phenomena of 

 gelatinization have been taken as the chief indices in the 

 differentiation of starches and it has been shown that a 

 considerable variety of reagents may be used. 



The terms gelatinized starch and soluble starch are 

 used synonymously, yet starch may be in a soluble form 

 without being gelatinized or gelatinizable, for it has 

 been shown that raw starch through the agency of acid 

 can be converted into soluble starch without apparent 

 antecedent change in the structure of the starch grain 

 that can be detected in the reaction of the grains in 

 polarized light ; that such grains can be dissolved in hot 

 water without the appearance of gelatinization ; and that 

 such grains in solid form or in solution yield the blue 

 starch-reaction with iodine. (See preceding memoir,* 

 page 105.) It is therefore obvious that the changes ex- 

 pressed by gelatinization and solubility are independent, 

 although usually associated; and, as a consequence, that 

 a gelatinizing reagent may give rise coincidently fo such 

 molecular alterations as will convert an insoluble into a 

 soluble and gelatinized starch or into a soluble but un- 

 gelatinizable starch. In all of the experiments with 

 these reagents the former change has been brought 

 about; but accompanying alterations may occur, hence, 

 the question naturally arises in conjunction with the 

 use of different reagents as to the meanings of the dif- 

 ferences in the two cases. 



It is of importance to note that in all of these investi- 

 gations the soluble non-gelatinizable form was prepared 

 by the use of acids, inorganic or organic, non-volatile or 

 volatile. On the other hand, as far as the voluminous 

 records go, alkalies always give rise to soluble starch 

 of the gelatinized form. This indicates clearly that the 

 actions of the acids and alkalies may be inherently quite 

 different. When the grains are heated in water, gela- 

 tinization occurs at a given temperature, varying within 

 narrow limits, the mean temperature differing in starches 

 from different sources. In accordance with the fore- 

 going, heat and alkalies may be placed in one and acids 

 in another category, but without the assumption that the 

 actions of the several members of each class are precisely 

 the same. Gelatinization is undoubtedly due to a hy- 

 dration of the starch molecules, but the alteration from 



• Carnegie Inst. Wash. Pub. No. 173 (1913). 



