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H2O2 Analysis in a "Peroxy-sulfuric"
Copper Etching Bath

Equipment Required:
  • Titration flask (125 ml)
  • 10 ml Automatic pipettor
  • Digital titrator
Reagents Required:
  • Ferroin indicator
  • 0.50N Cerric solution

Procedure:

  1. Measure 30 mL of deionized water into the titration flask. This will constitute the analysis environment and as such the measured quantity is not critical.
  2. Add one drop of Ferroin indicator.
  3. Using the automatic pipetter, add 0.10 mL of sample etchant. Swirl the flask around to mix the solution thoroughly. The mixture should be bright orange in color.
  4. Using the digital titrator, titrate with the .50N Cerric until the solution goes from orange to colorless (or light blue). Record the number of drops of titrant used as indicated on the digital readout (denote the digital titrator reading NumPerox).
  5. If NumPerox is less than 503 drops, the hydrogen peroxide (H2O2) content of the bath must be adjusted. Assuming a bath volume of V liters, the amount needed to raise the concentration to the optimum 10% (vol) may be calculated using:
Liters of 50% H2O2 needed = (0.10-.0001788 x NumPerox) x V

Or, if you are using H2O2 with a concentration different than 50% (wt.), use the formula:

Liters of H 2O2 needed ={(0.05-.0000894 x NumPerox) x V} / concentration of H2O2 (wt.)

Note: If you are using a bath based on the FT-2 catalyst system, you should replenish the FT-2 in concert with any addition of H2O2. To replenish FT-2 use:

Liters of FT-2 needed = 0.33 x liters of 50% H2O2 added

To express the concentration of H2O2 (100%) as a percent of bath volume, use:

% H2O2 = .00894*(NumPerox)

The acceptable range of digital titrator readings for total hydrogen peroxide content is:

Acceptable Range (%): 4 to 5.5
NumPerox: 447 to 615

Example

A reading of 350 drops would indicate that the addition of approximately 1.4 liters of 50% H2O2 would be sufficient to return a 38 liter bath to its original peroxide level.

CAUTION

50% Hydrogen Peroxide is a very strong oxidizing agent and will cause severe burns if brought into contact with the skin, eyes, etc. If such contact should occur, immediately flush affected area with cool water for 15 minutes. CONTACT A PHYSICIAN IMMEDIATELY.

HANDLE WITH CARE

Always wear protective clothing, acid resistant gloves, and a full coverage face shield when handling this or any other corrosive material.


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