296 PHYSIOLOGICAL CHEMISTRY. 



output of ammonia occurs since the salt is oxidized and its nitrogen 

 ultimately appears in the urine as urea. 



The acids formed during the process of protein destruction 

 within the body have an influence upon the excretion of ammonia 

 similar to that exerted by acids which have been administered. 

 Therefore a pathological increase in the output of ammonia is ob- 

 served in such diseases as are accompanied by an increased and im- 

 perfect protein metabolism, and especially in diabetes, in which 

 disease diacetic acid and /?-oxybutyric acid are found in the urine 

 in combination with the ammonia. 



As the result of recent experiments Folin claims that a pro- 

 nounced decrease in the extent of protein metabolism, as measured 

 by the total nitrogen in the urine, is frequently accompanied 

 by a decreased elimination of ammonia. The ammonia elimination 

 is therefore probably determined by other factors than the total 

 protein catabolism as such. Furthermore, he believes that a de- 

 cided decrease in the total nitrogen excretion is always accompanied 

 by a relative increase in the ammonia-nitrogen, provided the food is 

 of a character yielding an alkaline ash. 



The quantitative determination of ammonia must be made upon 

 the fresh urine since upon standing the normal urine will undergo 

 ammoniacal fermentation (see page 257). 



Sulphates. 



Sulphur in combination is excreted in two forms in the urine; 

 first, as loosely combined, unoxidized or neutral sulphur and second, 

 as oxidized or acid sulphur. The loosely combined sulphur is ex- 

 creted mainly as a constituent of such bodies as cystine, cysteine, 

 taurine, hydrogen sulphide, ethyl sulphide, thiocyanates, sul- 

 phonic acids, oxyproteic acid, alloxpyroteic acid and uroferric acid. 

 The amount of loosely combined sulphur eliminated is in great 

 measure independent of the extent of protein decomposition or of 

 the total sulphur excretion. In this characteristic it is somewhat 

 similar to the excretion of creatinine. The oxidized sulphur is 

 eliminated in the form of sulphuric acid, principally as salts of 

 sodium, potassium, calcium and magnesium; a relatively small 

 amount occurs in the form of ethereal sulphuric acid, i. e., sulphuric 

 acid in combination with such aromatic bodies as phenol, indole, 

 skatole, cresol, pyrocatechin arid hydroquinone. Sulphuric acid in 

 combination with Na, K, Ca or Mg is sometimes termed inorganic 

 or preformed sulphuric acid whereas the ethereal sulphuric acid is 



