Disposal of TNT-> TNB chromium waste
So I followed the procedure in the COPAE for the preparation of trinitrobenzene from trinitrotoluene. After separation of the TNBzOOH from the
sulfate/chromate solution and decarboxylation of the TNBzOOH in water followed by recrystallization of the TNB from ethanol, small solid black
particles remain trapped at the bottom of the beaker between the TNB and the glass. These are insoluble in water.
The solution from which the TNBzOOH was isolated is pitch-black, but upon dilution with water it reveals itself to be a dark emerald green.
Since the COPAE was written well before Silent Spring, it makes no mention of disposing of the chromium waste.
From the appearance and some of the properties (soluble in acidic media [in this case aqueous H2SO4], greenish color), I'm assuming this is
chromium(III) oxide.
Now, chromium(VI) compounds (such as the sodium dichromate I started with) are highly carcinogenic, but I've heard nothing about chromium(III)
compounds.
My concerns are as follows:
The trinitrobenzene has a slightly greenish cast to it, even after multiple cycles of granulation under boiling water, decantation, and
reconstitution of the molten material, followed by recrystallization from hot ethanol. Is there appreciable chromium inside the trinitrobenzene, or is
that its natural color? It reminds me very closely of 2,4-dinitrochlorobenzene, not the yellow of picric acid or the light brown of TNT.
What is the best method for disposing of chromium(III) oxide, both as a solid powder and as a solution in aqueous acid?
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