696 URINE. 



inine interferes with TROMMER'S test for sugar, partly because it has a 

 reducing action, and partly by retaining the copper suboxide in solution. 

 The compound with copper suboxide is not soluble in a saturated soda 

 solution, and if a little creatinine is dissolved in a cold saturated soda 

 solution and then a few drops of FEHLING'S reagent added, a white flocculent 

 compound separates after heating to 50-60 C. and then cooling (v. 

 MASCHKE's 1 reaction). An alkaline bismuth solution (see Sugar Tests) 

 is not reduced by creatinine. 



An aqueous solujbion of creatinine is precipitated by picric acid. 

 The precipitate consists on recrystallization from hot water, of thin, 

 silky, pale yellow needles (JAFFE). If the urine is treated with picric 

 acid (20 cc. of a 5 per cent solution in alcohol for each 100 cc. urine), 

 then a double picrate of creatinine and potassium is precipitated (JAFFE). 

 If a solution of creatinine in w&ter (or urine) is treated with a watery 

 solution of picric acid and a few drops of a dilute caustic-soda solution, 

 a red coloration, lasting several hours, immediately occurs at the ordinary 

 temperature, which turns yellow on the addition of acid (JAFFE'S 2 reac- 

 tion). Acetone gives a more reddish-yellow color. Glucose gives 

 with this reagent a red coloration only after heating. If we add a few 

 drops of a freshly prepared very dilute sodium-nitroprusside solution 

 (sp.gr. 1.003) to a dilute creatinine solution (or to the urine) and then a 

 few drops of caustic soda, a ruby-red liquid is obtained which quickly 

 turns yellow again (WEYL'S S reaction). If the cold yellow solution is 

 neutralized and treated with an excess of acetic acid, a crystalline pre- 

 cipitate of a nitroso-compound (C^eN^C^) of creatinine separates on 

 stirring (KRAMM) or creatininoxim (SCHMIDT 4 ). If, on the contrary, 

 the yellow solution is treated with an excess of acetic acid and heated, 

 the solution becomes first green and then blue (SALKOWSKI 5 ) ; finally 

 a precipitate of Prussian blue is obtained. 



A reaction which in description is similar and which, although not solely 

 (ARNOLD) but at least partially (HOLOBUT), appears after partaking of protein 

 food or meat soup is ARNOLD'S reaction. 6 This reaction is due to an unknown 

 endogenous metabolism product. If 10-20 cc. urine are treated with a few drops 

 of a 4 per cent sodium nitroprusside solution and then with 5-10 cc. of a 5 per 

 cent sodium or potassium hydroxide solution, at first a strong and pure violet 

 color is obtained with an absorption band between D and E, then it becomes 

 purple-red and then brown-red and finally yellow. On the addition of acetic 



1 Zeitschr. f. analyt. Chem., 17. 



2 Zeitschr. f. physiol. Chem., 10. 



3 Ber. d. deutsch. chem. Gesellsch., 11. 



4 Kramm, Centralbl. f. d. med. Wissensch., 1897; Schmidt, cited from Chem. 

 Centralbl., 1912, 2. 



5 Zeitschr. f. physiol. Chem., 4. 



6 Arnold, Zeitschr. f. physiol. Chem., 49 and 83; Holobut, ibid., 56. 



