eutech-instruments lead epoxy User Manual

Instruction Manual 

 

Lead Electrode

 

 

5

The temperature of the standard solutions and of the sample solutions should be the same and below 
80

o

C. About a 4% error in the slope will occur for each 1oC difference in temperature. 

 
Interferences should be absent. If they are present, use the procedure found in the 

 

and 

 sections to remove them. 

 

 
Lead concentrations are measured in units of ppm as lead, moles per liter, or any other convenient 
concentration unit.  Table 1 indicates some concentration units and conversion factors. 
 
    TABLE 1:  Concentration Unit Conversion Factors 
 
  ppm 

Pb

+2

    

     M      

ppm SO

4

-2

 

   

 

20.7 

 1.0X10

-4

    

  9.6 

   

207.0 

 1.0X10

-3

      

 96.0 

  2070.0 

 1.0X10

-2

      

960.0 

 
 
MEASUREMENT PROCEDURE 
 

 
Direct measurement is a simple procedure for measuring a large number of samples. A single meter 
reading is all that is required for each sample. The ionic strength of samples and standards should 
be made the same by adjustment with ISA. The temperature of both sample solution and standard 
solution should be the same. 
 

 

1. 

By serial dilution, prepare 10

-2

M, 10

-3

M, and 10

-4

M or 100 ppm and 10 ppm standards, 

from the 0.1M or 1,000 ppm standards.  Prepare standards with a composition similar to 
the samples if the samples have an ionic strength above 0.1M. 

 
2. 

Place 50 ml of the 10

-4

M or 10 ppm standard in a 150 ml beaker and add 50 ml of 

methanol-formaldehyde solution. Place the beaker on the magnetic stirrer and begin 
stirring at a constant rate. Add 2 ml of ISA. After assuring that the meter is in the mV 
mode, lower the electrode tips into the solution. When the reading has stabilized, record 
the mV reading. 

3. 

Place 50 ml of the 10

-3

M or 100 ppm standard in a 150 ml beaker and add 50 ml of 

methanol-formaldehyde solution. Place the beaker on the magnetic stirrer and begin 
stirring. Add 2 ml of ISA. After rinsing the electrodes with distilled water, blot dry, and 
immerse the electrode tips in the solution. When the reading has stabilized, record the mV 
reading. 

 
4. 

Place 50 ml of the 10

-2

M or 1,000 ppm standard in a 150 ml beaker and add 50 ml of 

methanol-formaldehyde solution. Place the beaker on the magnetic stirrer and begin 
stirring. Add 2 ml of ISA. After rinsing the electrodes with distilled water, blot dry, and 
immerse the electrode tips in the solution.  When the reading has stabilized, record the mV 
reading.