[alt-photo] Re: Zia standard solutions

[Terry King]

Dear Loris


Thank you for the explanation which would  need further explanation on a workshop.  While I fully accept that an understanding of the chemistry is important, remember that people have come to make pictures.


Thank you too for the offer of a one to one explanation but I did look into this when my daughter was doing her GCSEs in 1994.  I have not needed to use it since as the concept of percentage dilutions is more easily grasped.


Useful background would be a list of molar concentrations for the  different states of chemicals used in alt processes with a separate column relating it to saturated solutions expressed in percentage terms. One could refer to this list if someone wants to know what the dilution should be when, for example,  only an anhydrous compound is available.   Is this something you would like to prepare for our benefit ?


Would it be helpful though in deciding which of the four states of EDTA would be used in clearing a platinum print ?  As  I find that Willis's method using 1% HCl is more effective, this would only be of academic interest.


Terry





-----Original Message-----
From: Loris Medici <mail at loris.medici.name>
To: 'The alternative photographic processes mailing list' <alt-photo-process-list at lists.altphotolist.org>
Sent: Wed, 21 Jul 2010 8:43
Subject: [alt-photo] Re: Zia standard solutions


Molar concentration helps where there's more than one variant of the
compound in the market, for instance, at various hydration states. E.g.
citric acid = anhydrous / monohydrate, trisodium citrate = dihydrate /
pentahydrate, oxalic acid = anhydrous / dihydrate, palladium chloride =
anhydrous / dihydrate and so on... If you know the molarity (instead of w/v
%) of the solution(s) you want to mix, then you can use each and every
variant of the compounds, by making a simple ratio calculation in order to
learn the equivalent weight of the replacement variant. If you don't know
the molarity, you're bound to the "specific" variant the formula calls for,
and sometimes that's really a problem - when you can't find it for
instance...

I do also give workshops Terry, would you like to take few lessons (a
private workshop) from me in this issue? (Explaining the principles to music
publishers and theology PhDs and such...) And that would be with the added
bonus of making visit to our beautiful Istanbul... ;) :P

Regards,
Loris.

-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org On Behalf Of
Terry King
Sent: Wednesday, July 21, 2010 2:32 AM
To: alt-photo-process-list at lists.altphotolist.org
Subject: [alt-photo] Re: Zia standard solutions

...

Try explaining to us what advantages ' .7 m '  offers over the equivalent
percentage solution figure, then imagine explaining the same thing, and how
you would measure it, to a workshop containing music publishers and theology
PhDs who have come to make pictures.

_______________________________________________
Alt-photo-process-list | http://altphotolist.org/listinfo