Chromic acid solution will remove organic matter, but will eventually embrittle
plastics. To minimize embrittlement, soak plastic for no more than 4 hours. The
following formula is the recommended cleaning agent:
Dissolve 120 grams of sodium dichromate (NA2Cr2O7CC2H2O)
in 1000 mL tap water. Carefully add 1600 mL concentrated sulfuric acid. Note:
Because this solution generates considerable heat, we recommend external
cooling. Do not mix in a plastic container.
This solution is designed to produce an excess of dichromate in the form of a
precipitate which actually extends the useful life of chromic acid and
dissolves as needed. This chromic acid solution can be used repeatedly until it
begins to develop a greenish color, indicating a loss of potency. As a result
of the excess dichromate built into this formula, the solution lasts much
longer than commercially available solutions.
Sodium hypochlorite solutions (bleach) are also effective in removing organic
matter. Use at room temperature.
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