[alt-photo] Re: On working with hydrochloric acid

[etienne garbaux]

Francis wrote:

>I do I five minute soak in each of two vinegar baths followed by a thorough
>rinse in tap water.

Excellent, using two baths is the right way to go.

>The first vinegar bath gets discarded after eight
>sheets of 22" x 30" FAEW have gone through.

That strikes me as quite a lot of paper, but then I don't know how 
much vinegar you are using in the bath.  What happens with the second 
bath?  Do you promote it to the first bath and make a new second 
bath, or keep using it as the second bath for some larger number of 
sheets?  (If 8 sheets is pushing the first bath, then promoting the 
second bath is probably not the optimal technique.)

>That's where I think the pH test strips would be useful (testing the first
>vinegar bath).

No disagreement from me, although the cheap little Ph meter pens may 
be more cost-effective and accurate.  They are commonly available in 
the $10-20 range these days, although there is a tier of better ones 
in the $50 range.  If you use the test strips, get ones that have the 
narrowest range that covers your intended depletion point -- strips 
with greater ranges are correspondingly harder to read.  Also, note 
that calcium acetate is slightly acidic in solution, so the bath will 
be below pH 7 even when fully exhausted.

Best regards,

etienne