244 CHEMISTRY OF THE PROTEIDS CHAP. 



From this last complex, hydrolysis would give rise to oxamide, 

 oxaminic acid, oxalic acid, and ammonia. 



000 



// / / 



C_NH 2 C OH C OH 



C NH 2 C NH 2 C OH 



\ \ \ 







Oxamide, oxaminic acid, oxalic acid. 



Oxamide was first obtained by Low : on oxidising egg-albumin 

 with KMn0 4 . He believed the oxamide to be formed secondarily out 

 of the HCN and the NH 3 set free by the oxidation of the albumin, 

 and this view is also shared by Hofmeister, 2 by Halsey, 3 and by 

 Ehrmann, as explained above, but Kutscher and Schenck 4 incline to 

 the view that oxamide occurs as such in gelatine, and state that the 

 biuret-reaction (see p. 141) may be partly due to it. They obtained 

 oxamide to the extent of 1/5 per cent on oxidising gelatine at 100 

 with 5 parts of calcium-permanganate and decomposing the slightly 

 soluble lime - salts with hot ammonium carbonate. Ammonium 

 oxaminate in considerable quantities and guanidin-picrate amounting 

 to 8 per cent of the gelatine were also found. The ammonium oxamin- 

 ate Schenck 5 derives from glycocoll, which gives rise to a substance 

 which Seemann 6 identified as oxalur-amide. The latter under the 

 influence of ammonia then breaks up into oxaminic acid and urea. 



CO- -NH X CO OH NH 2 v 



yCO + H 9 = | + " >CO 



CO.NH 2 NH/ CO.NH 2 NH/ 



Oxalur-amide or oxalan, oxaminic acid, + urea. 



From the oxaminic acid, oxalic acid [CO . OH] 2 is formed 

 secondarily, and this explains the oxaluria which Lommel 7 produced 

 by feeding animals on gelatine, for the latter is very rich in glycocoll 

 or the mother- substance of oxalic acid. Casein, which is poor in 

 glycocoll, yielded only traces of ammonium oxaminate when oxidised 

 by Kutscher and Schenck. 



That it is possible to synthetise urea or oxaminic acid from such 



1 0. Low, Journ. f. prakt. Chem. [2] 31. 129 (1885). 



' 2 F. Hofmeister, Arch. f. experim. Pathol. u. Therapie, 37. 426. 



3 Halsey, Zeit. f. physiol Chem. 25. 325 (1898). 



4 Fr. Kutscher and M. Schenck, Ber. d. deutsch. chem. Ges. 38. 455 (1905). 



5 M. Schenck, ibid. p. 459. 



6 J. Seemann, Zentralbl. f. Physiologic, 18- 285 (1904), and Zeitschr.f. physiol. Chem l 

 44. 229 (1905). 7 LommeJ, Deutsch. Arch. f. klin. Med. 1899. 



