URIC ACID. 663 



minutes it is diluted with water to 500 cc. and mixed. This solution 

 is now compared in a DUBOSCQ colorimeter with a 1 /2 normal potassium- 

 dichromate solution. The latter solution has in a layer 8 mm. thick 

 exactly the same intensity of color as a layer 8.1 mm. thick of a solution 

 of 10 milligrams creatinine after the addition of 15 cc. picric-acid solu- 

 tion and 5 cc. NaOH solution and dilution to 500 cc. The calculations 

 are simple. For example, in case the urine tested in a layer 7.2 mm. 

 thick has the same color as the dichromate solution in a layer 8 mm. 

 thick, then the quantity of creatinine in 10 cc. of the urine will be 



O I 



= ^X10, or 11.25 milligrams. This method has been tried by many 



authorities and found to be trustworthy. 



The same method is used in the determination of creatine, which 

 for this purpose is first converted into creatinine by warming with dilute 

 mineral acid. The quantity of creatine is the difference obtained between 

 the values for creatinine before and after treatment with acid. More 

 detailed directions can be found in the cited works of FOLIN, v. HOOGEX- 

 HUYZE and VERPLOEGH, GOTTLIEB and STANGASSINGER. 



In regard to other methods, see the works of KOLISCH and GREGOR. 1 



Xanthocreatinine, C 5 H 10 N 4 O. This body, which was first prepared from meat 

 extract by GAUTIER, has been found by MONARI in dog's urine after the injection 

 of creatinine into the abdominal cavity, and in human urine after several hours 

 of exhaustive marching. According to COLASANTI it occurs to a relatively greater 

 extent in lion's urine. STADTHAGEN 2 considers the xanthocreatinine isolated 

 from human urine after strenuous muscular activity as impure creatinine. 



Xanthocreatinine forms thin sulphur-yellow plates, similar to cholesterin, 

 which have a bitter tastfe. It dissolves in cold water and in alcohol, and gives 

 a crystalline compound with hydrochloric acid and a double compound with 

 gold and platinum chloride. It gives a compound with zinc chloride, which 

 crystallizes in fine needles. Xanthocreatinine has a poisonous action. 



Methylguanidine occurs, according to ACHELIS, KUTSCHER and LOHMANN, 

 to a slight extent as a regular constituent of the urine of man, horse and dog. It 

 has been found in urines associated with dimethylguanidine by ENGELAND. S 



HN-CO 



Uric Acid, Ur, GsI^N^s; 2, 6, 8-trioxypurine, OC C-NH V , has 



I II >0 



HN-C-NH' 



been prepaied synthetically by HORBACZEWSKI by fusing urea and 

 glycocoll or by heating trichlorlactic-acid amide with an excess of urea. 

 BEHREND and ROOSEN prepared it from isodialuric acid and urea; it 

 is also readily produced from isouric acid on boiling with hydrochloric 



1 Kolisch, Centralbl. f. innere Med., 1895; Gregor, Zeitschr. f. physiol. Chem., 31. 



2 Gauiter, Bull, de 1'acad. de med. (2), 15, and Bull, de la soc. chim. (2), 48: Monari, 

 Maly's Jahresber., 17; Colasanti, Arch. ital. d. Biologic, 15, Fasc. 3; Stadthagen, 

 Zeitschr. f. klin. Med., 15. 



3 Achelis, Centralbl. f. Physiol., 20, 455, and Zeitschr. f. physiol. Chem., 50; Kut- 

 scher and Lohmann, ibid., 49; Engeland, ibid., 57. 



