ESTIMATION OF PURINE BASES. 679 



cyanide according to VOLHARD'S method. The ammonium-sulphocyanide 

 solution should contain 1.2-1.4 grams 'per liter, and its strength should 

 be determined by a silver-nitrate solution: 1 part silver corresponds 

 to 0.277 gram nitrogen of purine bases or to 0.7381 gram purine bases. 

 By this method the uric-acid and purine bases can be simultaneously 

 determined in the same portion of urine. 1 



MALFATTI 2 determines the nitrogen of the purine bases in the hydrochloric- 

 acid filtrate from the separated uric acid. This filtrate is evaporated with mag- 

 nesia until all the ammonia has been expelled and the residue used for the KJEL- 

 DAHL determination. 



The nitrogen of the purine bases is also determined as the difference between 

 the uric-acid nitrogen and the total nitrogen of the purine bodies of the silver 

 precipitate (CAMERER, ARNSTEIN 3 ). SALKOWSKI has raised the objection to 

 this procedure that it is not possible to remove all the ammonia from the silver 

 precipitate by washing. According to ARNSTEIN 4 this can readily be done by 

 boiling the precipitate in water with some magnesia, and under these circum- 

 stances this method is quite serviceable. The nitrogen is estimated by KJEL- 

 DAHL'S method. The uric-acid nitrogen multiplied by 3 gives the quantity of 

 uric acid. As the mixture of purine bases in the urine is but little known, the 

 quantity of nitrogen of the purine bases is always calculated as a certain purine 

 base, for example xanthine (CAMERER), and the quantity so found used as a 

 measure for the purine bases. 



According to a new method of KRUGER and SCHMID 5 the uric acid and the 

 purine bases are precipitated as a cuprous compound by copper-sulphate solu- 

 tion and sodium bisulphite. The precipitate is decomposed in sufficient water 

 by sodium sulphide, and the uric acid precipitated from the concentrated filtrate 

 with hydrochloric acid, and the purine bases again precipitated from this filtrate 

 as cuprous or silver compounds. Finally, the nitrogen in the uric-acid part and 

 the part containing the mixture of purine bases is estimated. 



We cannot discuss the other methods, such as those of DENIGES and NIEMI- 

 LOWICZ, and the method suggested by HALL 8 for clinical purposes. 



Oxaluric Acid, C 3 H 4 N 2 O 4 =(CON : H 3 ).CO.COOH. This acid, whose relation 

 to uric acid and urea has been spoken of above, does not always occur in the 

 urine, and then only in traces as the ammonium salt. This salt is not directly 

 precipitated by CaCl 2 and NH 3 , but on boiling it is decomposed into urea and 

 oxalate. In preparing oxaluric acid from urine the latter is filtered through 

 animal charcoal. The oxaluric retained by the charcoal may be obtained by 

 boiling with alcohol. 



COOH 



Oxalic Acid, C2H 2 O4, or . , occurs under physiological conditions 



COOH 



in very small amounts in the urine, about 0.02 gram in twenty-four hours 

 (FiJRBRiNGER 7 ). According to the generally accepted view it exists in 



1 In regard to the details we refer the reader to the original paper. 



2 Centralbl. f. innere Med., 1897. 



3 Camerer, Zeitschr. f. Biologic, 26 and 28; Arnstein, Zeitschr. f. physiol. Chem., 23. 



4 Salkowski, 1. c.; Arnstein, Centralbl. f. d. med. Wissensch., 1898. 



5 Zeitschr. f. physiol. Chem., 45 and Hoppe-Seyler-Thierfelder's Handbuch, 8. 

 Aufl., 590. 



8 Niemilowicz, Zeitschr. f. physiol. Chem., 35; Gittelmacher-Wilenko, ibid., 36; 

 Hall, Wien. klin. Wochenschr., 16. 



7 Deutsch. Arch. f. klin. Med., 18. See also Dunlop, Journ. Path, and Bacteriol., 3. 



