Glacial + Indicator Stop

acoma · Jul 12, 2013

Just thinking, I have about equal parts glacial acetic and Kodak indicator stop bath. Anyone see any problems with mixing them together and diluting accordingly for use? The glacial acetic's about 10 years old & I'd hate to see it go to waste. The indicator should still turn color when the combined working solution is expired, although the color saturation would be much diluted, right?

Tom1956 · Jul 13, 2013

I have half full gallon bottle of glacial I've had since 1978. My vote is to keep it It sure came in handy last year when I had a squirrel infestation between my roof layers. Pour a little of that on a rag and hold it near the opening they found, and they were out of there in no time, and never came back. I didn't want to use poison and have dead bodies up there. That is some mean stuff. Some day you'll have something you will find a very good use for.

zsas · Jul 13, 2013

Tom what a great story!!!! You gave them the choice of their fate, looks like they chose the correct path.

polyglot · Jul 13, 2013

Or just use the glacial at about 1.5% dilution and don't bother with indicator. When it no longer smells vinegary (acetic acid becomes various acetates after neutralisation) then chuck it.

Nicholas Lindan · Jul 13, 2013

Glacial doesn't go bad. A gallon of glacial lasts a long, long time. It makes almost 70 gallons of working strength stop bath.

I do use a combination of Kodak Indicator Stop bath and 28%: 33ml of 28% + 6ml of indicator -> 1 liter of working strength.

The indicator in Kodak's product isn't ideal as by the time the bromo-cresol purple changes color the stop bath has been worthless for quite some time. I pitch the bath when the color changes from orange to pale yellow. It has been suggested that bromo-cresol green would be a better indicator.

An even longer lasting staple is a gallon jug of Photo-Flo 600, equal to 600 gallons of working Photo-Flo.

Gerald C Koch · Jul 13, 2013

The problem in the original question is that the strengths of glacial acetic acid and Kodak Indicator Stopbath are different. Mixing them together would create a solution of unknown strength. Better to use each alone until one is used up.

cliveh · Jul 13, 2013

Use up the glacial first and then stick with indicator.

Herzeleid · Jul 13, 2013

Just an idea, why not measure the PH of the diluted indicator stop bath and prepare glacial acid solution of identical PH and mix them both. The final ph won't deviate dramatically. Diluted indicator dye will work regardless of the dilution, only the ph of the solution matters.

If it is any help, Dead Link Removed

winger · Jul 13, 2013

Buy some 30% hydrogen peroxide and some cupric chloride to add to the glacial acetic and do some Mordançage.
I would use it separately from the indicator version, though, and just dump each working solution when it no longer stinks.

acoma · Jul 14, 2013

Thanks, a wealth of knowledge here as always! Separate it is, then.

I'd grown to prefer odorless stop in recent years but ran out unexpectedly. There were these two bottles of acetic on the shelf that got me thinking...usually a bad thing.

Tom1956 · Jul 14, 2013

Glacial mixes 3:8 to get 28%. Then use 6 oz 28% to the gallon of water. That simple.

Nicholas Lindan · Jul 14, 2013

Nicholas Lindan said:
I use a combination of Kodak Indicator Stop bath and 28%: 33ml of 28% + 6ml of indicator -> 1 liter of working strength.

The above mixture proportions take into account the differing acid concentrations of the two.

Gerald C Koch · Jul 15, 2013

Tom1956 said:
Glacial mixes 3:8 to get 28%. Then use 6 oz 28% to the gallon of water. That simple.

May I add that when diluting concentrated acids always add the acid to the water never the other way around

Tom Taylor · Jul 15, 2013

Why not use citric acid? It has no odor, easy to mix, and is very inexpensive.

Thomas

Athiril · Jul 16, 2013

Gerald C Koch said:
The problem in the original question is that the strengths of glacial acetic acid and Kodak Indicator Stopbath are different. Mixing them together would create a solution of unknown strength. Better to use each alone until one is used up.

The indicator will still indicate at the pH change.

You can always just dilute the stop bath as normal, and add a small volume of glacial acetic acid to this when the pH indicator indicates it's bad, thus lowering the pH again the indicator will switch back to the normal colour.

Gerald C Koch · Jul 17, 2013

I have never really seen the need for indicating stop baths. I never attempt to save used stop bath and my feet usually give out before the stop bath does.

In addition acetic acid has its own built in indicator that is its smell. When the bath no longer smells like acetic acid it should be discarded. Easy and simple.

KennyMark · Jul 17, 2013

silveror0 said:
My high school chem teacher told us an easy way to remember that sequence. She said acid > water is "aw wight."

Mine taught us "Do as you oughta, add acid to watah". The efficacy of mnemonic devices is proven daily.

erikg · Jul 17, 2013

KennyMark said:
Mine taught us "Do as you oughta, add acid to watah". The efficacy of mnemonic devices is proven daily.

Great! With a Rhode Island accent even. That's wicked smaht.

Glacial + Indicator Stop

acoma

Tom1956

zsas

polyglot

Nicholas Lindan

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Gerald C Koch

cliveh

Herzeleid

winger

acoma

Tom1956

Nicholas Lindan

Advertiser

Gerald C Koch

Tom Taylor

Athiril

Gerald C Koch

KennyMark

erikg

Glacial + Indicator Stop

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