[TheForge] Phosphate? (Ping Bruce the chemist)

[Bruce .]

Well, consider me pinged.

I'm an organic analytical chemist, so chemistry like this is a little out
of my line -- I have to hearken back to my undergrad studies ...

I strongly recommend checking Wikipedia for information on chemicals.  It's
by no means perfect (and in particular, some folks seem to be debating
whether iron phosphate is suitable for slug-killing in organic gardens --
which is what happens  in a democratically run info source), but it does
contain the basic info.  However, I understand that if one doesn't have a
background in chemistry, interpreting the info that's there can be daunting.

Most likely, the iron is now oxidized to ferric ion ( Fe[III] ), making the
bulk of your gunk ferric phosphate.  Possibly the darker layer on top was
ferrous ( Fe[II] ), as ferrous phosphate is slightly less dense and >might<
have precipitated more slowly (but that's a stretch).

I doubt you'll find any use for it, but sufficiently diluted it is at least
not environmentally toxic, and may have value as a fertilizer.
(Howsomever, you MIGHT have toxic metals in the mix -- like lead and
cadmium.  Zinc and copper and some others are less of a concern.)

There is a CHANCE it could be used as a rust-proofing, provided it could be
distributed over the surface of steel.  That could be done by mixing it
with a paint body (e.g., boiled linseed oil, or casein -- tho the latter is
water-soluble) and applying it to the metal.  Whether it could be used w/o
the paint body I don't know.  That may depend what the stuff decomposes TO
when heated.  One reference I found suggests that it decomposes to ferrous
phosphate -- and that probably would provide rust protection.  Why not try
it on two identical bars?  Heat both to red, set one aside (as a control),
and treat the other with the gunk.  Set them out in the weather and keep an
eye on them.

How's life otherwise?

Bruce
NJ

On Mon, Jul 16, 2018 at 5:37 PM, Mike Spencer <mspencer at tallships.ca> wrote:

>
> I had a background in chemistry, too, but I was weak on inorganic and
> it was 50 years ago so...
>
> I had some phosporic acid that I used to pickle some ironwork, maybe 3
> gal. diluted from the 80-something % as delivered.
>
> It sat in a plastic gas can for years.  When I went to get some, the
> can held a large quantity of solid gunk and a murky supernatant.  Much
> shaking and proddind with a stick, dumped out a slurry into a tray,
> allowed the liquid to evaporate in the sun over several days.
>
> Result was a thin layer of black stuff on top, I assume iron
> phosphate.  Scraped that off and allowed the remainder to dry.  It's a
> uniformly light grey, gritty granular substance.  Seems insoluable or
> only slightly soluable in water.  Will melt, perhaps with
> decomposition, on an iron bar when the bar is heated with a torch to
> orange heat.
>
> Must be something-or-other phosphate but I can't figure out what it
> is.
>
> What's my grey granular substance, Bruce, that came from phosporic
> acid in a closed container with only a litte iron contmaination?
>
>
> Feeling stupid, presbyphoria,
> - Mike
>
> --
> Michael Spencer                  Nova Scotia, Canada       .~.
>                                                            /V\
> mspencer at tallships.ca                                     /( )\
> http://home.tallships.ca/mspencer/                        ^^-^^
>
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