[alt-photo] Re: dilution of pt/pd - weak black from B&S

[EJ Photo]

It may very well be that not enough time was given to the FO solution to get
completely dissolved, it may be that the addition of the acid, allowed for
it to complete the process. How soon after mixing did you try and use the
solution of FO?  

Eric Neilsen
Eric Neilsen Photography
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> I had one student who bought some pure ferric oxalate from B & S, good
stuff, nothing wrong with it, but it did not produce good platinum prints in
the same way as the ferric oxalate as we had made in class without using
molar solutions. The problem was solved by adding oxalic acid to the B & S
solutions. unsurprisingly,we deduced that the ph of the dilution had to be
more acid.  From other experience we also deduced that he it needed to be an
organic acid. Why should that be ?