FUMARIC ACID THAT IS SPECIFIED AS FOOD GRADE 99.8%
SWIM has acquired some fumaraic acid though the labelling on the order does say food grade, it is chinese and as SWIM cannot read the labelling SWIM needs a sure fire way of determining whether it contains any toxic heavy metals e.g: Lead.
SWIM knows one way to do so and that would be, to dissolve fumaric acid in cold water - or cold acetone in the first place as fumaric acid dissolves better in acetone I think. (Cold to increase precipitation/decrease solubility)
use a double displacement reaction with a compound such as sodium sulphide, to precipitate a compound like Lead sulphide which is insoluble and black so therefore would provide a indication on whether is it contaminated.
^this is only an example of one heavy metal to detect.
But for sake of argument. After the lead sulphate is precipitated, depending on the original counterpart of the lead SWIM could also be left with sodium nitrate, sodium carbonate, sodium chloride and so on..
which are insoluble in acetone but are soluble in water.. SWIM has theorized..
SWIMS question is (providing SWIM puts his safety first and won't consume anything unless SWIM has proof) if both of the new compounds are insoluble in acetone, could one filter the water out to collect the first lot of precipitate (mainly being lead sulphide) then precipitate the rest in acetone. (sodium-? + lead sulphide) filter extensively and be left with fumaric acid + one final addition of sodium sulphide to check for any more colour and precipitation?
If there was no more precipitation and colour (basically no reaction at all) would that mean such compounds have been removed?

Or is it possible to simply go ahead, make the dmt fumerate salt and washed it afterwards, something that metal ions dissolve in and dmt fumerate salt does not?

I'm not looking for throw it away or find another source as its basicly unbuyable over here, I'm looking for a way to do it however I know if I am not 100% that is has worked and it is scientifically correct I'm not stupid enough to try it anyway.

IT IS MOST LIKELY FOOD GRADE ANYWAY BUT I LIKE TO MAKE SURE AMD HOW WILL I KNOW IF ITS FOOD GRADE LIKE IT SAYS. WITH A PRECIPITATION REACTION?