[pure-silver] Re: chemical purity
- From: titrisol <titrisol@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 5 Jan 2005 08:36:45 -0800 (PST)
the ig advantage of using arm and hammer or swimming pool
products is that heavy metals are limited since this products
are regulated as for "human use"
--- "Koch, Gerald" <gkoch02@xxxxxxxxxx> wrote:
> How pure are the chemicals your are using to compound your
> developer? I mention
> this because there have been some comments recently about fog
> with certain
> formulas.
>
> Commercial grade triethanolamine can contain 15%
> diethanolamine. This will
> raise the pH of developers made with it above what would be
> expected. This can
> cause higher fog levels and contrast and density problems.
> Diethanolamine has
> an ammonia like odor and its presence should be easily
> detectable since
> triethanolamine should be odorless. If you have any doubts
> about the purity or
> are experiencing problems you might also ask the supplier.
> BTW, the grade
> supplied by The Chemistry Store is 99% pure.
>
> Another chemical where source is important is ethylene or
> propylene glycol.
> Using antifreeze as a substitute is not a good idea as it
> usually contains other
> ingredients (such as rust inhibitors) which may not be
> photographically neutral.
>
> One should always be careful when using any technical grade
> chemical for
> photographic purposes. Test any new supply thoroughly before
> using it for
> critical photos.
>
> Some companies such as Arm & Hammer and US Borax post MSDS's
> for their products
> which are very useful for determining suitability for
> photographic purposes.
> Check for iron and other metal impurity limits.
>
> Jerry
>
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