CHAPTER III. 



PRIMARY AND REVERTED DECOMPOSITION PRODUCTS OF STARCH, 



When proteins are subjected to the actions of various hydrolytic agents, such as dilute 

 acids, alkahes, and proteoclastic enzymes, a number of complex non-protein, non-colloidal 

 derivatives or unit structural substances or decomposition products are formed which, 

 because of their close relationship to the parent substances, have been termed the "pri- 

 mary dissociation products." These have been found to differ quantitatively and quali- 

 tatively in different proteins; and in certain instances, as in the protamines, differences 

 have been noted which lead to the belief that with better methods of technique the con- 

 stitutions of corresponding proteins will be found by chemical methods to differ, as has 

 been shown by the crystallographic method in the case of the hemoglobins (see Preface, 

 page vi) ; and, moreover, that such differences will be found to be specific in relationship 

 to genera, species, etc. The starch-molecule likewise yields non-colloidal derivatives, 

 which, as in the case of the proteins, are closely related to the parent substance and which 

 also, with better laboratory methods, will in all likelihood be found to possess consti- 

 tutional characteristics peculiar to the kind of starch. In case of both protein and starch, 

 in the decomposition processes giving rise to the non-colloidal derivatives, there are inter- 

 mediate colloidal products formed which as yet are but Uttle understood as individuals or 

 in their relations, or in the exact processes that occur during their formation. 



The starch-molecule is conceived to be a complex polymer. According to Findlay (Physi- 

 cal Chemistry and its AppHcations in Medicine and Biological Science, London, 1905, 63) 

 the apparent osmotic pressure of boiled starch leads to the value of 25,000 for the molec- 

 ular weight. Skraup (Monatsb. f. Chemie, 1905, xxvi, 1415), by means of an acetylchlor 

 compound, estimated the molecular weight of soluble starch to be 7,440. Fouard (Compt. 

 rend., 1908, cxlvi, 285, 978) prepared a non-colloidal solution of starch, having the mobility 

 of pure water, by filtering a pseudo-solution of partially demineralized hydrated starch at 

 80° tlii-ough a collodion membrane. He found that cryoscopic examinations showed no 

 falling of the freezing-point, and that the lowest possible molecular weight must be at least 

 15,000. This solution, he records, showed by ultra-microscopic examination no diffracting 

 Ijarticles, and that it stands between the mineral colloids of insoluble elements and fully 

 dissociated salt solutions. Assuming that the molecular weight is 15,000, and that the 

 molecular formula is n(C6Hio05)n, the molecule would, according to almost universal 

 conceptions, be regarded as bemg composed of over 90 single groups of CqHioOs, the groups 

 probably existing in the molecule in multiples of 3 or more; but the assumed existence of 

 such preformed groups can not be admitted, as has been pointed out in Chapter I, page 6. 



When comminuted raw starch or boUed starch is subjected to the actions of weak acids, 

 hot glycerol, amyloclastic enzymes, etc., the starch-molecules are broken down into a 

 number of complex primary decomposition products which, as far as oiu- limited knowledge 

 goes, are in the form, chiefly or entirely, of dextrins and sugars. Since a number of 

 these products have been described, and as some differences have been noted in them when 

 obtained from different starches under both like and unlike conditions of experiment, 

 the probability is suggested that starches from different sources of origin, if they are not 

 identical in chemical constitution, might exliibit specific differences in their derivatives, 

 and thus afford a method of specific differentiation of starch in relation to genera, species, 



83 



