[pure-silver] Re: Fixer Hydration
- From: titrisol <titrisol@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 26 Jan 2005 08:10:14 -0800 (PST)
To dissolve crystalline thio the trick was using a "tea bag"
Just put the thiosulphate in a piece of cheese cloth
["hypo-bag"]
Put water in a bucket/wide mouuth bottle and put the "hypo-bag"
hanging on the top of the container.
A few hours later (over night was my preference) the hypo will
be dissolved without effort.
--- Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
> Sodium Thiosulfite comes as crystals or in anhydrous form
> (sometimes called dessicated). Older formulas generally
> specify crystaline thiosulfate but the anhydrous form is
> used for packaged fixers because of its light weight and
> because it will dissolve in luke-warm water. Crystaline hypo
> is strongly endothermic so one must start with very hot
> water to get it into solution. In fact, crystaline hypo
> going into solution was a common chem lab trick to form a
> cooling bath when ice was not avialable. Anhydrous
> thiosulfate is exothermic but has little heat of solution.
> It will dissolve readily in water at around 80F.
> At one time (perhaps still) there was a "Photo" grade of
> chemicals. These were not necessarily exceptionally pure but
> were guarateed not to contain impurities known to affect
> photographic processing. Photography does not always require
> very pure chemicals but does require that certain
> contaminents not be present. Often commercial grade
> chemicals will do quite well and are cheap. Reagent grade
> (called something else now I think) are always pure enough
> for photo work but they come with an assay of impurities
> which makes them expensive. Note that they may not be
> outstandingly pure, its that the impurities are known and
> listed.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
>
>
>
>
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