Acid Bath Preparation and Neutralization Protocol
Author: William C. Eddy; Updated: March 2007
Goal
This protocol details preparation and neutralization of acid baths used for cleaning glassware.
Supplies/Equipment Needed
- HCl
- Phenolphthalein Indicator
- Ethanol
- NaOH
- Plastic tub for HCl
- Stir Plate
- Magnetic Stir Bar
- pH Strips
- Fume Hood
Acid Bath Preparation
Prepare 10% HCl by filling H2O up to the first dashed line on the Acid bath tubs and then slowly add HCl into tub until liquid reaches the second dashed line.
Acid Bath Neutralization
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Add 10-20 drops phenolphthalein indicator per 10L 10% HCl. (to make indicator: 4 g Phenolphthalein into 400 mL 100% ethanol).
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Place acid bath tub onto stir plate inside fume hood.
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Add a stir plate magnet and turn stir plate on med/high (DON’T TURN ON THE HEAT).
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Add NaOH or other strong base (can be waste or old base) to acid bath, stirring, until bath turns a light pink color (at pH 8.4).
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Make sure Acid Bath is between pH 7-9 before pouring down drain. If you overshoot pH 9, you can use HCl to bring the pH back down (can use other old acid bath 10% HCL to bring pH back down).
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Once acid bath is faint pink dump it down the drain and scrub clean the tubs.