HYDROGEN ION CONCENTRATION 25 



3. The only mineral acids found in significant amounts in urine 

 which belong to the class of weak acids, and therefore form salts 

 which show the above behavior, are phosphoric and carbonic acids. 



4. Very weak bases form salts which behave like those of the 

 weak acids. Creatinine is titrated almost quantitatively in chang- 

 ing the hydrogen ion concentration from 10~ 3 to 2X10~ 3 , and 

 creatine to about 60 per cent. Aside from the traces of amino- 

 acids, these appear to be the only bases of this kind present in 

 considerable amount in human urine. 



HYDROGEN ION CONCENTRATION OR TRUE 

 ACIDITY 



Indicator Method 

 (Henderson and Palmer's Adaptation of Sorensen's Method) l 



Principle. The reaction of the urine is estimated by matching 

 the colors produced when a few drops of indicator are added 

 respectively to the diluted urine and to standard solutions of known 

 reaction similarly diluted. Similar hydrogen ion concentrations 

 are indicated by similar colors. The indicator must be properly 

 chosen. 



Standard Solutions. A series of standard solutions of known 

 hydrogen ion concentration must be prepared. The solutions as 

 indicated in Table I (page 26) are satisfactory for urine analysis. 

 The table also indicates the H ion concentration of each solution, 

 the figure given being the logarithm of this concentration (P H +)- 

 It is more convenient and rational to express the concentration 

 by this logarithmic notation. True H ion concentrations cor- 

 responding to the logarithmic figures are given in Table II 

 (page 26). 



The thirteen solutions indicated are made up by mixing equal 

 volumes of their ingredient solutions of the composition indicated. 

 Solutions 4 to 12 are all that are ordinarily required, as the normal 

 urinary H ion concentrations lie between 4.80 and 7.50 and path- 

 ological variations are usually within these limits. The mean 

 normal value is almost exactly 6.00. 



1 Henderson and Palmer: Jour. Biol. Chem., 1913, 13, 393. 



