94 CHEMISTRY OF THE PROTEIDS CHAP. 



Here may also be mentioned Friedenthal's 4 views on the oxida- 

 tion of albuminous substances in living organisms. As completely 

 dry carbon will not burn in completely dry oxygen, he has arrived at 

 the conception that oxidation depends on an accumulation of OH-ions; 

 on subjecting various foodstuffs to the oxidising action of alkalies, 

 i.e. of Off-compounds, he found albumins, colloidal carbo-hydrates, 

 fats and soaps not to become oxidised, while the lower dissociation 

 products of albumins and carbohydrates readily became oxidised. As 

 the higher albuminous substances are broken up in the body, it is 

 assumed that they are hydrolysed in the first instance before being 

 oxidised. 



The oxidation of uric acid in alkaline solutions is discussed by 

 Behrend. 2 



(d) Dissociation ~by Means of Acid, and Treatment of the Resulting Ammo- 

 Adds with Nitrous Acid and Reduction with Metallic Sodium 



By this means Ducceschi 3 obtained from egg-white, serum-albumin 

 and horn ; and Spiro 4 from casein and gelatin, cinnamic acid, which is 

 derived from phenyl-alanin. 



C TT C 6 H 5 



65 f!H 



PTT ^-n- 



n 2 "NTH _ II 

 CHNH 2 - ^ H 



COOH. 



Phenyl-alanin ammonia = cinnamic acid. 

 By an analogous process aspartic acid gives rise to fumaric acid. 



COOH 



_ 

 CHNH 2 3 



COOH COOH. 



Aspartic acid ammonia = fumaric acid. 



(e) Disintegration with Nitric Acid 



This method produces entirely different results. Miihlhauser, 5 

 v. Fiirth, 6 and Habermann and Ehrenfeld 7 have boiled casein with 



1 H. Friedenthal, Arch. f. (Anat. und) Physiol. 1904, p. 371. 



2 Behrend, Liebig's Annalen, 333. 141 (1904). 



a V. Ducceschi, Hof master's Beitrage, 1. 339 (1901). 



4 K. Spiro, ibid. 1. 347 (1901). 



5 Miihlhauser, Liebig's Ann. 90. 171 (1854), 101. 176 (1857). 



6 0. v. Fiirth, Strassburger Habilitationsschrift, Strassburg, 1899. 



7 J. Habermann and E. Ehrenfeld, Zeitschr. /. physiol. Ghem. 35- 231 (1902). 



