SolderOn Lead Analysis

Equipment Required:

• Titration flask (125 ml)
• 10 ml Automatic pipette
• Digital titrator
• 1 mL syringe
• 0.5g and 1.0g measuring spoons

Reagents Required:

• CDTA, 0.800M titration cartridge
• pH 6.00 buffer powder pillows
• Hexamethylenetetramine
• Hydrogen peroxide, 30%, ACS
• Methylthymol blue indicator powder pillows
• Rochelle salt

Procedure:

1. Using the syringe, measure 5 mL of bath into the 125 mL flask. Add approximately 45 mL of deionized water.
2. Using the 0.5 g measuring spoon, add 1 spoonful of Rochelle salt and swirl to dissolve.
3. Add 1 mL of 30% hydrogen peroxide and swirl gently to thoroughly mix. Wait approximately 1 minute to allow the peroxide to oxidize the dissolved tin.
4. Using the 1 g measuring spoon, add 1 spoonfil of hexamethylenetetramine to the sample and swirl to dissolve.
5. Add the contents of 1 ea. PH 6.0 buffer powder pillow and swirl to dissolve.
6. Add the contents of 1 methylthymol blue powder pillow and swirl to dissolve. The sample solution should now be blue.
   
   If the sample does not turn blue, the pH is too low. Add an additional 1 g spoonful of hexamethylenetetramine before proceeding.
   
   
7. Titrate the sample with CDTA solution to a straw-yellow endpoint. Record the number of digits (NUMLEAD) needed to reach the endpoint.
8. To determine the concentration of dissolved lead (Pb metal), use:
   
   

   Pb (metal) = NUMLEAD x 0.0414 g/l

   
   or
   
   

   Pb (metal) = NUMLEAD x 0.00553 oz/gal

   
   
9. Assuming that you are using LeaRonal SolderOn Lead Concentrate (SLC) with 450 g/l lead metal and want to operate your bath at the optimum point of 11g/l of lead metal, the amount needed to replenish the 38 liter (10 gallon) bath is given by:
   
   

   SLC needed = (266 - NUMLEAD) x 0.0035 liters

   
   or
   
   

   SLC needed = (266 - NUMLEAD) x 0.00092 gal.

   
   The acceptable range of digital titrator readings is:
   
   

   Acceptable Range Pb metal:	9.0 to 13.0 g/l
   NUMTIN:	217 to 317

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