Tim Williams wrote:

This morning I poured out the
solution. It was all orange, like slightly diluted orange pop. No smell
anything like the mercaptan. Nor did the orange look like rust, although
it may have been, bleach I believe being an oxidizer.


Oh, undoubtedly. Once you open it to air, there's nothing to protect the
metal. Propane is a hydrocarbon, but with its boiling point, tends not to
stick around too long.

I get the same orange juice appearance from leaving water sit in soup cans
too long, although it's usually a bit chunkier than the colloidial
suspension you must've had.

I did some Web research this morning. It appears that methyl mercaptan dissolved
in a 5% bleach solution does indeed turn red/orange/brown colored. So it wasn't
rust. And to put the (unneeded) cap on it, there are a lot of official-looking
Web sites which say methyl (or ethyl, or butyl ..) mercaptan can be deodorized
with a 5% sodium hypochlorite solution, better known as household bleach. So
my method of pouring in 1-2 cups of bleach, plugging and sloshing thoroughly,
then unplugging and hot water rinsing is about as good as you can do. - GWE