HCl in Ferric Chloride Solutions (RDM-5004)Procedure for Analysis
Ferric Chloride is reduced to Ferrous by addition of Sodium Thiosulfate solution, so that it does not interfere with titration. Solution is then titrated with 0.100N Sodium Carbonate to pH 4.00. Sodium Carbonate will neutralize HCl, but will not precipitate metals present, like NaOH would.
- Saturated Sodium Thiosulfate solution
- 0.100N Sodium Carbonate solution
- pH 4.0 Buffer
- 5.00 ml volumetric pipet
- 50 ml buret
- pH meter
- Magnetic stirrer
- 250 ml flask
Pipet 5.00 mls of the ferric chloride solution to be tested into flask, dilute to 100 mls with deionized water. Add saturated Sodium Thiosulfate solution, one drop at a time, until solution turns (sort of) clear, and further addition does not produce cause additional brown/black color to form. This will require about 5 mls. (Excess Sodium Thiosulfate will cause titration to be low) Place (standardized) pH meter electrode in solution, and titrate with 0.100N Sodium Carbonate solution to pH 4.00, note mls required.
Grams/liter HCl = mls 0.100N Sod. Carbonate X 0.729 Or: %HCl ≈ mls 0.100N Sodium Carbonate X 0.052
* This procedure originally developed by Buckbee Mears Corp.