eutech-instruments ammonia gas Manuale Utente

Instruction Manual 

 

Ammonia Gas-sensing Electrode

 

 

13

 

It is possible to calculate the ratio of ammonia to ammonium ion, theoretically, if the pH is known.  
A. Martell and R. Smith in Critical Stability Constants, Plenum Press, New York, 1974, state: 
 
                    [NH

4

+]          [NH

4

+]        

      

      

⎯⎯⎯⎯  =  ⎯⎯⎯⎯    K ~ 10-9.3 

                    [H

3

O+]          [NH

3

]       10-

pH 

[NH

3

] 

  
                 

at 25oC, X = 0.1 where pH ~ 9.3 

The ratio of ammonium to ammonia is given by: 
 
                [NH4+] 
              

⎯⎯⎯⎯ = K-pH = 10 9.3-pH 

 

                 [NH3] 
Both temperature and ionic strength will cause the exact value of K to vary. If, for example, while 
the pH at 25

o

C and X = 0.1 is 9.3, an increase in ionic strength to X = 1.0 yields a pH of 9.4, at 

25

o

C. 

 
TROUBLESHOOTING GUIDE 
 
The goal of troubleshooting is the isolation of a problem through checking each of the system 
components in turn: the meter, the glassware the electrodes, the standard and reagents, the sample, 
and the technique. 
 

The meter is the easiest component to eliminate as a possible cause of error. Most meters are 
provided with an instrument check-out procedure in the instruction manual and a shorting strap for 
convenience in troubleshooting. Consult the manual for complete instructions and verify that the 
instrument operates as indicated and is stable in all steps.