84 THE NITROGENOUS DERIVATIVES OF THE ALBUMINS. 



The relation of uric acid to the mono-ureids of the second order, 

 finally, is shown by treating one part of uric acid with three parts 

 of nitric acid (50 per cent, solution), and heating to 70 C. On sub- 

 sequent evaporation to a syrup and cooling, parabanic acid crystal- 

 lizes out, and on decomposition yields urea and oxalic acid : 



(1) C 5 H 4 N 4 3 + H 2 + O = C 4 H 2 N 2 4 + CO (NH,), 



Alloxan. 



(2) C 4 H 2 N 2 4 + O = C 3 H 2 N 2 3 + CO 2 



me 

 acid. 



(3) C 3 H 2 N 2 3 + 211,0 = C 2 H 2 4 + CO(NH 2 ) 2 



Oxalic acid. 



Guanin, as has been shown, under the same conditions yields 

 guanidin and parabanic acid, which further illustrates the close 

 relationship between the two classes. 



For a consideration of the methods employed in the isolation of 

 uric acid and its quantitative estimation, the reader is referred to the 

 chapter on the Urine. 



THE KREATINS. 



The kreatins, or Jcreatinie leucomains, as they are also termed by 

 Gautier, are basic substances which are closely related to the 

 nucleinic bases and to the ureids, which have just been considered. 

 They comprise kreatin, kreatinin, crusokreatinin, xanthokreatinin, 

 amphikreatinin, and two similar substances of doubtful composition. 

 Kreatin, moreover, is related to arginin, and can be produced syntheti- 

 cally through the union of cyanamide and methyl-glycocoll, as arginin 

 results from cyanamide and ornithin. While arginin, however, can 

 be obtained artificially from albuminous material, kreatin has thus 

 far not been isolated in this manner. Its formation from cyanamide 

 and methyl-glycocoll is represented by the equation : 



/NH 2 

 N = C NH 2 + NH(CH 3 ) CH 2 COOH = NH = C< 



\N(CH 3 )-CH 2 -COOH 

 Cyanamide. Methyl-glycocoll. Kreatin. 



It is thus a homologue of glycocyamin, which results through the 

 union of cyanamide and glycocoll : 



X NH 2 

 N = C NH 2 + CH 2 NH 2 COOH = NH 2 = C< 



\NH CH 2 COOH 

 Cyanamide. Glycocoll. Glucocyamin. 



On dehydration kreatin loses one molecule of water and is trans- 

 formed into kreatinin, which may thus be regarded as the anhydride 

 of kreatin : 



/NH 2 /NH CO 



NH = C< = NH - C/ -f H 2 



\N(CH 3 ) CH 2 COOH X N(CH 3 ) CH 2 



