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topic 8976

Sodium hydroxide analysis of alkaline zinc


What indicator do you suggest I use for analysis of sodium hydroxide in alkaline non cyanide zincs? The one used at present is BDH 11-13 but this is no longer available.

Philip Gormley
plating services - Irvine ,Ayrshire, Scotland


Try using Sulfo-orange or phenolpthalein. I use the sulfo-orange for cyanide based solutions. It might work. I use the phenolpthalein for alkaline cleaners.

I'm not at work until Tuesday, at which time, if you want I can try a couple of experiments and get back to you.

K. Gendron
- Trenton, ON, Canada


1. 5 ml. sample into a 250 ml. flask.

2. Add 25 ml. 20 % barium carbonate.

3. Add 3 drops phenolphthalein indicator.

4. Titrate with 0.1 N hydrochloric acid, color change is pink to white.

5. mls. titrated x 1.06 = oz/gal.

Bill Hemp
tech svc. w/ chemical supplier - Grand Rapids, Michigan


In response to the NaOH Titration procedure of Alkaline Zinc At our shop we use 5 ml sample 20 ml water A few specks of Indigo Carmine Indicator Titrate with 1.0N HCl from yellow to blue mls titrated * 0.95 = OZ/GAL * 7.5 = gms/lt

Lee Moss
- Calgary, Alberta, CANADA


We gave up on indicators and now use a pH meter and stirrer this gives more repeatable results. End point pH 11.2

Martin Trigg-Hogarth
Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England

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