>I still think that the solution when used should be disposed of as
>household hazardous waste. The residue from derusting car parts (paint and
>other gunk) has to be bad for the environment.
The paint and "other gunk" should probably be removed by some other method
prior to using phosphoric acid. Then your acid bath can be used several
times before its strength drops. The resulting solution contains a lot of
iron phosphate, which is a fantastic fertilizer, thus the suggestion to
pour it on your garden.
This thread was discussed here a couple of years ago; I have an expanded
discussion of the chemistry involved if anyone wants a copy of it.
Lee M. Daniels Laboratory for Molecular Structure and Bonding Texas A&M
daniels@lmsbvx.tamu.edu (409) 845-3726 Fax (409) 845-9351
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