Things you will need: Two cups, water, a T-shirt, a refrigerator, a rubber band, and a thick card (credit card would work).
Steps:
1. Crush the pills you want to extract the acetaminophen from into a very fine powder. A good way to do this is break the pills up into small fragments and then "twist" the card in a circular manner over the pills. (Hopefully that makes sense). Be sure you are on a hard surface (important). Also make sure the powder is as fine as it can be, no chunks!
2. Fill a cup with about 1 to 1 1/2 inches of warm water. (The less water the better, you just have to make sure everything is COMPLETELY dissolved and that the water is not saturated). You will have to increase the volume of water depending on how much powder you have.
3. Place the solution into the freezer. Since opiates are water soluble at low temperatures, and acetaminophen is not water soluble at all (only at extreme temperatures) , the opiate will separate itself from the acetaminophen and dissolve into the water. This should take approximately 15 minutes. The goal is to get the solution as close to 32 degrees without freezing it. Keep checking on it until you see a thin film of ice or until you see the edge of the water beginning to freeze to the edges.
3. Take your T-shirt and soak it, or just the part you are going to use, in cold water. Take another empty cup and put the T-shirt on top of the mouth in a concave fashion so that the shirt is dipping into the cup. The more you can get the shirt to dip into the cup the better. Take a rubber band and use it to hold the T-shirt into place. A T-shirt does not have to be used... some people use coffee filters but I HIGHLY discourage this.
4. Pour the solution into the cup with the T-shirt on it slowly. Use a funnel if you have one. The water will drip through the T-shirt (pretty quickly if you use a T-shirt) and into the cup leaving almost all of the acetaminophen filtered out. You will literally be able to scrape the liver killing scum off of the shirt. A lot of the water will be absorbed into the T-shirt itself so it is important to wring the water out into the cup. I would suggest scraping off the acetaminophen before doing this.
5. What you will have left is a solution consisting primarily of water and opiates, with a fraction (If that) of the acetaminophen left.