Re: GMS help - paging Dick Dapson!
In recent posts about the Gomori methenamine silver (GMS) stain, we've
touched on the problems of disposing of the chromic acid oxidant.
Janet Crookham Dapson and Richard W. Dapson's "Hazardous Materials in the
Histopathology Laboratory" 3rd ed., Anatech 1995 (page 195) suggests:
"To reduce the volume of [chromium] waste, add sulfuric acid to dichromate
solution [or I suppose chromic acid solution?] to get the pH down to 1.0; add
solid sodium thiosulfate until solution turns cludy and blue. Neutralize with
sodium carbonate. Let mixture stand overnight and filter off the precipitate.
Discard the liquid down the drain if other ingredients permit; collect the
precipitate (chromium trioxide) for disposal by a licensed waste firm."
Dick Dapson, could you elaborate on this rather scary procedure? Does it need
to be done under a hood - how much sulfur dioxide and carbon dioxide does it
generate? How do you measure the pH? - I wouldn't care to dip a pH meter in
it. What are the chemical reactions and what are the molar quantities of the
<< Previous Message | Next Message >>