Extracting an undissolved powder/suspension from oil
I came across a post in another chemistry forum that made me think about some things from a long time ago (almost 2 decades well before I was into
chemistry) where people on a forum were trying to extract a micronized powder that was in an oil suspension (it would settle to bottom & needed
shaking). The powder was about 2.5g or 5g / 50ml and was suspended in an oil solution (possibly with 1/4 - 1/2% volume benzyl alcohol -> oil for
bacterostatic reasons).
I know that one powder was water soluble (possibly an acetate) and a different compound wasn't. The powder was in oil suspension for injection b/c
the oil helped disperse the powder where if it was dissolved in water, the water would be absorbed quickly and supposedly large crystals formed in the
area (from the dissolved compound) creating a lot of pain and scar tissue. The oil stopped this from happening for both of the compounds.
Also, both compounds were not soluble in alcohol (ethanol or IPA).
I remember some people saying that they extracted the powder for some reason. In both cases they put the oil suspension in equal parts water (50ml)
and heated/stirred. The acetate supposedly dissolved in the water and the other compound fell down into the water after settling for a few hours(oil
floated to the top and dropped the suspension/powder).
They would often add alcohol to the water that had the dissolved compound and it would crash out into crystals - but some remained in the water -
which was slowly evaporated and process was repeated to ensure no oil remained.
For the compound that didn't dissolve in water, it settled to the bottom, decanted the oil/water and washed with with alcohol and dried.
This was supposedly how they would extract the powders from an oil suspension. It seemed plausible at the time, never needed to try it so I just
remember reading about it. Does this seem like a plausible or workable approach? Is there a method of extracting undissolved powders from an oily
mess - is there a name for this kind of thing?
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