eutech-instruments silversulfide epoxy Manuel D’Utilisation

Silver/Silver Sulfide Electrode 

 

Instruction Manual 

 

20

5. 

If using jeweller's rouge, place a cotton ball on the table top and flatten it using the bottom 
of a beaker. 

 
6. 

Put 1-2 drops of distilled or deionized water in the center of the cotton pad. 

 
7. 

Add a small amount of jeweller's rouge to the damp cotton. 

 
8. 

Continue with Steps 3 and 4 above. 

 
 

 
The upper limit of detection in pure silver nitrate solutions is 1M. In the presence of other ions, the 
upper limit of detection is above 1.0x10

-1

M silver, but two factors influence this upper limit. Both 

the possibility of a liquid junction potential developing at the reference electrode and the salt 
extraction effect influence this upper limit. Some salts may extract into the electrode membrane at 
high salt concentrations, causing deviation from the theoretical response. Either dilute samples 
between 1M and 1.0x10

-1

M or calibrate the electrode at 4 or 5 intermediate points. 

 
The lower limit of detection is influenced by the slight water solubility of the electrode pellet.  
Refer to Figure 1 and Figure 2 for a comparison of the theoretical response to the actual response at 
low levels of sulfide and silver.   
 
pH Effects 
Silver reacts with hydroxide ions to form a precipitate of Ag

2

O, in ammonia-free basic solutions.  

By keeping all solutions slightly acidic, this can be avoided. Adjust the pH of silver solutions below 
8, if necessary, with 1M HNO

3

. 

 
Bisulfide ion (HS

-1

) and hydrogen sulfide (H

2

S) result when hydrogen ion complexes sulfide ion.  

Larger amounts of sulfide ion are complexed as the pH is lowered. The use of SAOB in all samples 
containing sulfide maintains a fixed level of S-

2

 ions, since the free sulfide ion (S

-2

) exists in only 

very basic solutions. In the acid range, sulfide is chiefly in the form of H

2

S, while in the pH range 

6-12, almost all the sulfide is in the HS-

1

 form. 

 
A silver/sulfide ion electrode will last six months in normal laboratory use. On-line measurements 
might shorten operational lifetime to several months. In time, the response time will increase and 
the calibration slope decreases to the point calibration is difficult and electrode replacement is 
required. 
 

 
The silver/sulfide electrode may be stored for short periods of time in 1.0x10

-2

M silver (or sulfide) 

solution. For longer storage (longer than two weeks), rinse and dry the sensing pellet and cover the 
membrane tip with any protective cap shipped with the electrode. The reference portion of the 
combination electrode (or the outer chamber of the reference electrode) should be drained of filling 
solution, if refillable, and the rubber insert placed over the filling hole.