The solubility of acetaminophen is quoted as 1 - 5mg per ml of water at 72°F.
Acetaminophen | C8H9NO2 | CID 1983 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological activities, safety/hazards/toxicity information, supplier lists, and more.
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Therefore, even if you used 100ml of water at room temperature the maximum amount of acetaminophen you could end up with in your final product is 500mg. This will be considerably less if you use refrigerated water. As codeine is more soluble, this will dissolve first leaving even less room for the acetaminophen.
So you physically cannot end up with a solution containing enough acetaminophen to be of concern.
I personally can't see the point of the freezer step. It takes too fuckin long.
I would crush the pills into a fine powder, mix thoroughly into 50ml water and stir for a couple minutes.
Then perform a course filtration. I use a piece of kitchen paper on top of a J cloth (both pre-wetted to eliminate absorption of the goodies).
Drape the filter over a suitable wide necked receptacle and make a depression in the middle. Pour the sludgy mixture into the middle of the filter, gather up the sides of the J cloth and squeeze the liquid through. The J cloth prevents the finer pored kitchen paper from tearing during the operation. Although squeezing the pre-wetted filter will introduce more water, it's still not enough to do you any harm. This will leave you with a cloudy solution in the receptacle and a dryish paste consisting mainly of acetaminophen, fillers and binders in the filter.
Then take the cloudy solution and filter again through a pre-wetted coffee filter. The absence of the fillers and binders makes this a relatively quick process. Even if the resulting filtrate is not perfectly clear, you're still good to go.
This operation can be completed in 10 minutes as opposed to waiting for freezing and settling and gives the same result.