Chromium (Smith's fixative etc) disposal

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From:"J. A. Kiernan" <> (by way of histonet)
To:histonet <>
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On Thu, 10 Dec 1998, Gayle Callis wrote:

> The EPA frowns on potassium dichromate being drain dumped.
> We collect and give it to our chemical safety facility
> for disposal.
                As what?

  Do these regulations apply to all the oxidation states of
  chromium? It is easy to reduce dichromate to chromic ions
  (as present in chrome alum), and in this lower oxidation
  state (3 rather than 6) chromium is present in all sorts
  of places, perhaps most notably in chrome-tanned leather,
  which is used for the softer and more colourful products
  of cow-hide, like gloves.

  The product of alkaline reduction of potassium dichromate
  is a polymeric green "chromium hydroxide," which is quite
  difficult to redissolve. Safety officers in the 1970s & '80s
  told us it was OK to send it down the drain. This was mostly
  the end-product of spent and neutralized "chromic acid" used
  for cleaning glass pipettes.  In the late '90s it's the
  fumes from incinerated plastic pipettes that they worry

  It costs very little to reduce a dichromate-containing
  solution. Add some formalin. Wait a few days. Add some
  strong ammonia. Wait a few days to let the unreacted
  ammonia evaporate. Wait several weeks until most of
  the water has evaporated (hood not needed because no
  fumes). Put the residual sludge in a plastic jar, for
  disposal as wet, insoluble mineral waste.

  At least some of the chromium toxicity scare comes
  from the electroplating industry, where large volumes
  of cyanide-containing solutions are used. This is a
  different kind of danger, well known since the turn
  of the century. Mists of chromium (? as) trioxide in
  refineries are another well known industrial hazard,
  hopefully now in the past.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1

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