56 URINE. 



ammonia, hippuric acid, creatinine, and traces of allantoin, 1 are precipi- 

 tated by a mixture of alcohol and ether after the addition of a solution 

 of barium chloride and barium hydroxide or in the presence of sugar with 

 solid barium hydroxide. The urea is determined in the concentrated 

 filtrate, after driving off the ammonia, by KJEDLDAHL'S nitrogen estima- 

 tion. Because of the slight error due to the presence of hippuric acid 

 and creatinine, several modifications have been suggested by SALASKIN 

 and ZALESKI and by BRAUNSTEiN. 2 These errors are best prevented, 

 according to MORNER, by the use of FOLIN'S method. 



Principle of Folin's Method. 3 On heating urea with hydrochloric 

 acid and crystalline magnesium chloride, which melts in its water of 

 crystallization at 112-115 C. and then boils at about 150-155 C., the 

 urea is completely decomposed, while no appreciable decomposition 

 of the hippuric acid and creatinine takes place. The ammonia produced 

 from the urea is distilled off and determined by titration. The amount 

 of ammonia previously existing in the urine must be specially determined. 



Determination of Urea by the Morner-Sjoqvist and Folin Method. 4 

 Five cc. of the urine are treated with 1.5 grams of powdered barium 

 hydroxide, and when as much of this is dissolved as possible by gently 

 mixing, it is precipitated by 100 cc. of the alcohol and ether mixture 

 (J vol. ether). On the following day it is filtered and the precipitate 

 washed with the alcohol and ether mixture. The alcohol and ether 

 are distilled off from the filtrate at about 55 C. (not above 60 C.). The 

 remaining liquid is treated with 2 cc. of hydrochloric acid of sp.gr. 

 1.124 (for 5 cc. urine), and carefully transferred to a flask of 200 cc. 

 capacity, and evaporated to dryness on the water-bath. Then add 20 

 grams of crytalline magnesium chloride to the contents of the flask 

 and 2 cc. of concentrated hydrochloric acid, and boil on a wire gauze 

 over a small flame for two hours, making use of a proper return cooler. 

 After cooling it is diluted to about J to 1 liter with water, the ammonia 

 completely distilled off after making it alkaline with caustic soda, and 

 the ammonia collected in standard acid. After boiling in order to drive 

 off the CO2 and cooling, the acid is retitrated. Corrections must be 

 made for the ammonia of the urine and for that contained in the magnes- 

 ium chloride. 



If a special determination of the preformed ammonia has been made, 

 then a direct treatment of the urine, according to FOLIN (nevertheless 

 after the evaporation of the urine with hydrochloric acid), gives good 

 results. In the presence of sugar the treatment of the urine with barium 

 hydroxide is absolutely necessary in MORNER'S opinion, otherwise the 

 humin substances produced from the sugar take up and retain nitrogen. 



1 According to Wiechowski, Hofmeister's Beitriige, 11, the quantity of allantoin 

 is so great in urine that it must be considered in this method. 



2 Braunstein, Zeitschr. f. physiol. Chem., 31; Salaskin and Zaleski, ibid., 28. 



3 Ibid., 32, 36, and 37. 



4 See Morner, Skand. Arch. f. Physiol., 14. 



