PHYSIOLOGICAL CHEMISTRY. 



FIG. 



-11 



flask a few drops of the acid distillate are shaken hack into the flask. 

 At the end of i J^ hours the contents of the vessel are transferred to 

 a i liter flask with about 700 c.c. of distilled water, about 20 c.c. of 

 10 per cent potassium hydroxide or sodium hydroxide solution is 

 added and the mixture distilled into a known volume of -^ sulphuric 

 acid until the contents of the flask are nearly dry or until the dis- 

 tillate fails to give an alkaline reaction 

 to litmus, showing the absence of 

 ammonia. The time devoted to this 

 process is ordinarily about an hour. 

 Boil the distillate a few moments to 

 free it from CO 2 , then cool and titrate 

 the mixture with -^ sodium hydroxide, 

 using " alizarin red " as indicator. 



A " check " experiment should al- 

 ways be made to determine the orig- 

 inal ammonia content of the urine and 

 of the magnesium chloride, if it is not 

 absolutely pure, which of course should 

 be subtracted from the total amount of 

 ammonia as determined by the above 

 process. 



The Folin method is extremely accu- 

 rate under all conditions except when 

 the urine contains sugar. When this 

 is the case the carbohydrate and the 

 urea unite, upon being heated, and 

 form a very stable combination. For 

 this reason the Folin method is not 

 suitable for use in the examination of 



such urines. The best method for use under such conditions is the 

 combination Morner-Sjoqvist-Folin method which is given below. 



4. Morner-Sjoqvist-Folin Method. As has already been stated 

 in the last experiment this method excels the Folin method in ac- 

 curacy only in the determination of urea in the presence of carbo- 

 hydrate bodies. Briefly the procedure is as follows : l Bring the 

 major portion of 1.5 gram of powdered barium hydroxide into 

 solution in 5 c.c. of urine in a small flask, and treat the mixture 

 with 100 c.c. of an alcohol-ether solution, consisting of two volumes 



1 The original description of the method may be found in an article by Morner: 

 Skaiidinavisches Archiv fiir Physiologic, 1903, xiv, p. 297. 



DOREMUS-HlNDS UREOMETER. 



