What is the acid percentage of Kodak Indicator Stop Bath concentrate?

[Steve Goldstein]

I have a couple of old bottles of the concentrate but neither states the concentration. Is it 28%, or something else? I'd like to know so I can do some semi-intelligent experiments acidifying used alkaline fix for electrolytic silver recovery.

Thank you.

 

[cowanw]

Weight % - Component - (CAS Registry No.)
Concentrate:
85-90
Acetic acid (000064-19-7)
10-15
Water (007732-18-5)
< 0.1
Bromocresol purple (000115-40-2)
or
Kodak indicator stop bath concentrate is around 95%
You choose

 

[Bob-D659]

Closer to 95% or so.

 

[Mike Wilde]

Is auto store sulfuric not more affordable?

 

[Photo Engineer]

Acetic Acid is soooo much more gentle on the skin!

PE

 

[bobwysiwyg]

Couldn't agree more. Sulfuric acid is nasty stuff to be avoided if not absolutely necessary for a particular application or function.

 

[holmburgers]

So diluted 1 to 63, does that mean a working stop bath is about 1.5% acid?

What about vinegar, where does that lie?

 

[DWThomas]

So diluted 1 to 63, does that mean a working stop bath is about 1.5% acid?

What about vinegar, where does that lie?

5% is pretty typical.

 

[DWThomas]

Hmmm - I may have been less than clear there, vinegar is typically 5%.

 

[gordrob]

So diluted 1 to 63, does that mean a working stop bath is about 1.5% acid?

What about vinegar, where does that lie?

I have always mixed mine at 16ml/L which is 1.6% Kodak's recommended dilution. Your 1:63 gives you the same dilution.

Gord

 

[holmburgers]

Hmmm - I may have been less than clear there, vinegar is typically 5%.

Thanks DW, I meant to ask actually. So diluting vinegar 1:2 or 333mL/1L would be about right I guess.

Thanks Gord... I actually prefer a mL/L measurement over this this:that biz!

If one could get a hold of some bromocresol purple cheap, making your own indicator stop bath might not be too difficult..

 

[RalphLambrecht]

View attachment BasicRecipesEd2a.pdf

 

[RalphLambrecht]

yes,1.5-2%acid for a working stop bath is about right. i use 15gof as corbic acid /literof water.