APPENDIX TO CHAPTER V 161 



leaflets on adding a slight excess of gold chloride to a concentrated 

 solution of creatinine hydrochloride at 40-50 ; the gold salt is readily 

 soluble in water and in alcohol and, after drying at 100, melts at 

 170-174 (Worner [1899]), 182-185 (Korndorfer [1904, 2])- 



Creatinine platinichloride, (C 4 H 7 ON 8 ).jH a PtCl 6 , crystallises in orange 

 red prisms and needles ; from water with 2H 2 O, from alcohol anhydrous 

 (Worner [1899]). It is soluble in about 36 parts of water (Top- 

 pelius and Pommerehne [1896]); hardly soluble in cold alcohol; 

 m.p. 220-225 on rapid heating. 



Creatinine oxime, C 4 H 6 O 2 N 4 , m.p. 250, is according to Schmidt 

 [1912] identical with " nitroso-creatinine " of Kramm. 



Colour reactions and estimation of creatine and creatinine. The only 

 colour reaction for creatine is the pink coloration produced by diacetyl, 

 CH 3 . CO . CO . CH 3 (Harden and Norris [1911]). This reaction is 

 also given by arginine and some other guanidine derivatives, but not 

 by creatinine. Walpole [1911] has used it for the direct estima- 

 tion of creatine in pathological urines. The usual method, however, is 

 an indirect one ; the creatine is converted into creatinine by heating 

 with acids (see above) and then estimated by Folin's method, described 

 below. 



The following are colour reactions for creatinine : 

 (a) Weyl's reaction [1878]; a freshly prepared very dilute 

 solution of sodium nitroprusside is added and then a few drops of 

 dilute caustic soda. In the presence of creatinine a ruby red colour 

 is produced ; acetone gives a similar coloration, and if present should 

 first be boiled off. The red colour due to creatinine is fugitive and 

 soon changes to yellow ; if then glacial acetic acid is added and the 

 solution is boiled, it becomes green and on standing a deposit of 

 Prussian blue is formed (Salkowski [1879]). This reaction is given 

 by hydantoins but not by creatine, and is still obtainable with pure 

 creatinine solutions containing 0*03 per cent, and urine containing 

 O'O66 per cent, of creatinine. 



(&) JafF6's reaction [1886]. The addition of aqueous picric 

 acid and a few drops of caustic soda produces in creatinine solutions 

 an immediate red coloration (orange to blood red). The colour in- 

 creases during the first few minutes and afterwards fades very slowly. 

 Limit I : 5000. Acetone gives a somewhat similar but much feebler 

 reddish yellow coloration, and if present should first be boiled off. 

 Aceto-acetic ester, hydrogen sulphide and particularly aceto-acetic 

 acid are the only other pathological substances which may interfere. 

 According to Chapman [1909] the coloration in Jaffe's reaction 



II 



