INTRODUCTORY DISCUSSION. 11 



hydrogen atoms. In the same group fall the metallic derivatives of glucose 

 and other sugars; these are already decomposed by such weak acids aa 

 carbonic acid. For the present purpose the most important property of 

 these metallic compounds is the fact that they decompose very readily ; far 

 more easily than the original alcohol or sugar. Thus, Nef * has shown that 



T> 



the salts of primary and secondary alcohols - R >CHOM (M=K, N"a, Ca, 



Ba, or Zn) dissociate at 180 to 250, while the corresponding free alcohols 

 dissociate at much higher temperatures, 400 to 600. Hence the salts are 

 much less stable and burn spontaneously in the air, while the free alcohols 

 are quite stable. 



A great deal of work has been done on the effect of alkalies and various 

 salts on the sugars.* One incentive to these investigations has been that the 

 reactions thus produced simulate in some regard the action of various 

 enzymes on sugars. The principle involved in these sugar reactions is the 

 same or very closely related to the action of the alcohols just indicated. A 

 few examples will suffice to illustrate. An aqueous solution of glucose is 

 affected but very slowly by the oxygen of the air or by hydrogen peroxide. 

 If, however, a trace of a salt of iron, for instance, is added to the mixture, 

 the glucose is oxidized rapidly with the evolution of much heat and the 

 formation of a large variety of compounds. An exceedingly small amount 

 of iron suffices to oxidize large quantities of sugar. 



In the presence of alkalies all the monosaccharides are unstable and 

 spontaneously decompose into a large variety of substances.* If the con- 

 centration of the alkali employed is very low, there takes place a series of 



*NEF, J. U. Dissociationsvorgaenge bei den einatomigen Alcoholen, Aethern, und 



Salzen. Liebig's Annalen der Chem., 318, 138, 1901. 

 3 FENTON, H. J. H. The oxidation of tartaric acid in the presence of iron salts. Jour. 



Chem. Soc., 65, 899, 1894. 



- , and H. JACKSON. Oxidation of polyhydric alcohols in the presence of iron. 



Jour. Chem. Soc., 75, 1-11, 1899. 



- , - . The oxidation of organic acids in the presence of ferrous iron. 



Jour. Chem. Soc., 77, 69-76, 1900. 



- , - . Degradation of glycolic aldehyde. Ibid., 77, 1294-1298, 1900. 

 MOBBELL, R. S., and F. M. CROFTS. Action of hydrogen peroxide on carbohydrates in 



the presence of ferrous salts. Jour. Chem. Soc., 75, 786-792, 1899; Ibid., 77, 

 1219-1221, 1900; Ibid., 81, 666-675, 1902; Ibid., 83, 1284-1292, 1903; Ibid., 

 87, 280-293, 1905. 



RUFF, OTTO. Ueber die Verwandlung der D-glucose in D-Arabinose. Ber. chem. 

 Ges., 31, 1573-1577, 1898. 



- . D- und R-Arabinose. Ibid., 32, 550-560, 1899. 



- . D-Erythrose. Ibid., 32, 3672-3681, 1899. 



OLLENDOBF, D. G. Abbau von D-Galactose und von Michzucker (D- und Galactoara- 

 binose). Ibid., 33, 1798-1810, 1900. 



- . Ueber die Oxidation der 1-Arabensaeure und 1-xylonsaeure. Ibid., 34, 



1362-1372, 1901. 



- . Ueber den Abbau der Rhamnon und Isosaccharin Saeure. Ibid., 35, 2360- 



2370, 1902. 



SPOEHB, H. A. On the behavior of the ordinary hexoses towards hydrogen peroxide 

 in the presence of alkaline hydroxides, as well as of various iron salts. 

 Amer. Chem. Jour., 43, 248-254, 1910. 



*NEF, J. U. Dissociationvorgaenge in der Zuckergruppe: III. Liebig's Annalen der 

 Chem., 403, 204, 1913. 



