Analysis of Hydrochloric in Ferric Chloride Etchant (RDM-5005)
Procedure for AnalysisTheory:
This method describes the procedure for the determination of free acidity in Ferric Chloride solutions. The Ferric is complexed with the Lithium Chloride, and extracted into MIBK, and the HCl remaining in the aqueous phase is titrated with standard base.
Reagents Required:
- 0.100N sodium hydroxide (NaOH)
- Saturated lithium chloride solution (about 10M): Dissolve approximately 610 grams of lithium chloride in deionized water and dilute to 1 liter.
- MIBK: Methyl iso-butyl ketone
Procedure:
Pipette a 5 ml aliquot of undiluted sample into small separator funnel and add 10 ml of saturated lithium chloride solution. Shake well, and let sit for 10 min. to complex the Fe3+. Add 15 ml of MIBK. and shake, and let sit for a further 10 min. to extract the complex. Remove lower layer from sep funnel, save, wash funnel with water, then again with sat. Lithium Chloride solution. Add back saved lower layer, and 15 more mls MIBK. Shake well, allow to separate completely. Remove lower layer to flask, dilute with deionized water, add few drops Methyl Orange indicator solution. Titrate with sodium hydroxide(NaOH) from red to orange, not yellow endpoint. Note mls required.
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.
Calculation:
Percent by volume (37%) Hydrochloric Acid = mls x 0.17 Or: % Active HCl ≈ mls NaOH X 0.052
RD Chemical presents these procedures in good faith, based on laboratory and field testing. Ultimate responsibility for propriety of use, however, must rest with the purchaser and user. RD Chemical Company recommends thorough testing of its products and procedures before use.