Re: Fuse in a Crucible ?

romek@ozemail.com.au
Fri, 21 Jul 1995 21:13:28 +1000

Judy, you must be the greeniest photographer in the World.
>Hello near & far:=20
>I have on hand the "Yearbook of Photography and
>Amateur's Guide 1907-8," which has, among other tidbits, a page headed
>"Treatment of Photographic Residues."=20
>
>These include old hypo, old platinotype baths, silver from sensitive
>films, etc. My concern at the moment is "solid residues (cuttings of
>silver paper, old filters, etc.)." Which is to say I'm trying to dispose
>of some 8 cartons of discarded gelatine-silver photographs accumulated
>over a period of years without hiring a truck to take them to a toxic
>waste site, or releasing them to a "regular" landfill -- or making a
>lifetime project out of the project.=20

Few words regarding silver recovery. First, silver is not toxic as such
(unless you are bacteria or other low life). Somre silver compounds are used
to desinfect potable water.=20
>The "treatment" outlined in this volume is "burn ... collect the ashes,"=20
>and "extract" the silver as follows:
Yes, burn them slowly to avoid transfer with hot air (as dust particles). So
burn it slowly, collect ash and mix with sodium carbonate and nitrate. In
theory you shouldn't have any organic matter in ash, so there is no danger
to mix with nitrates. If scared, add a bit of water. Cover your pot and heat
to melt (fuse) the mixture in a crucible. I would use an old cast iron pot.
You cannot use aluminium. Platinium is a bit too expensive. Your closed wood
stove is probably too cold, so use LPG or metahne-air instead. You really
need more than 500=B0C. During reaction some nitrogen oxides can escape
(toxic), so ventilation is important. A crucible is a vessel made of china
(porcelain) or nickel or platinium. In years of my chemical career, I
haven't seen anything else. Yes, nitrates are used in explosives. Nitrates
are strong oxidizers, but need some "fuel" (except for ammonium nitrate)
like charcoal, sulfur. When your mixture is well fused, cool it down,
dissolve in water and precipitate silver as salt. With some modifications
you could obtain a metallic silver. If you take on account all emissions,
energy used to manufacture carbonates, nitrates, it may be better to dump
your paper scraps in the landfill. Anyway, it is mainly paper, some gelatine
(easily decomposed) and small amount of metallic silver won't hurt. IMO=
anyway.

Roman

romek@ozemail.com.au