430 URINE. 



in the retort often reddens litmus paper more strongly than before. 

 In this case the acid phosphate of soda exerts a decomposing action 

 on the urea or on the pigment (probably on both), and there is 

 formed phosphate of soda and ammonia, which, as is well known, 

 evolves ammonia at a temperature of 100, and again becomes con- 

 verted into acid phosphate of soda; hence it exerts a continuous de- 

 composing action on these nitrogenous matters during evaporation, 

 and thus the urine may retain its acid reaction, while a large amount 

 of an ammoniacal fluid passes over into the receiver. If we boil acid 

 phosphate of soda with pure urea, or with the alcoholic extract, 

 after freeing it from all bases and from ammonia by sulphuric acid, 

 and saturating the sulphuric acid with potash or soda, we may 

 readily satisfy ourselves of the correctness of this mode of explain- 

 ing this singular phenomenon. On treating urine that has been 

 concentrated by freezing with bichloride of platinum and alcohol, 

 there is a precipitation of chloride of platinum and potassium, but 

 no precipitation of platinum and ammonium ; on adding caustic 

 potash to such urine, the precipitate, when examined with the 

 microscope, does not exhibit the well known star-like groups of 

 laminae of basic phosphate of ammonia and magnesia, but merely 

 amorphous matter ; and further, no ammonia can be detected in 

 this precipitate by any chemical test. 



It is universally known that ammoniacal salts occur in morbid, 

 alkaline human urine; but we also sometimes find ammo- 

 niacal salts in the acid urine of patients, as I have convinced 

 myself in examining the perfectly fresh acid urine of typhous 

 patients. It is, however, extremely difficult to determine the 

 quantity of ammonia with any moderate degree of accuracy, whether 

 we apply bichloride of platinum according to Liebig's* method, or 

 magnesian salts, as recommended by De Vry,t since urine of this 

 nature has generally a great tendency to decomposition, and no 

 conclusion can be deduced from a single specimen ; for in the 

 determination of the ammonia, it is necessary to employ the urine 

 collected in a definite period. On this account also it is difficult 

 to decide in what forms of disease we especially find acid urine to 

 contain ammonia. 



The following is De Vry's method of determining ammonia quan- 

 titatively in urine. Fresh urine is treated with bicarbonate of soda 

 in order to remove the earths, is filtered, and sulphate of magnesia 

 is then added to it ; in consequence of the presence of phosphate 



* Ann. d. Ch. u. Pharm. Bd. 50, S. 195, 

 t Ibid. Vol. 59, p. 383. 



