The Amateur Chemist

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Extracting Dichloromethane from Paint Stripper

Dichloromethane (DCM)—or methylene chloride—is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents (Wikipedia).

Dichloromethane is a widely used extraction solvent. For many of the upcoming extractions on this website, I will be using dichloromethane. It can be used to extract vanillan from vanilla, cinnamaldehyde from cinnamon, and caffeine from any caffeinated drinks, to name just a few uses. It is an extremely common solvent, and it is always good to have around.

The method of extraction we are going to use is distillation. If you have a distillation setup, then great. If you don't, then you can try to distill it right out of the can. There is quite a good YouTube video on doing this you should watch. Either way, distillation is the easiest way to separate the DCM from the paint stripper. The brand I used is called "Klean Strip (KS) 3 Premium Stripper". You can get it at Walmart and quite a few hardware stores. It comes in about 1 quart containers for about $9. This brand has about 70% DCM in it, and the rest is methanol and petroleum distillates. It is quite thick, and it may be hard to get in a distillation flask, but it will work eventually. Don't get it on your hand, as it actually burns the skin for a bit.

When you distill it, you can take everything up to around 40-45 degrees Celcius. DCM boils at 39.6 degrees Celcius. The longer you collect, the more methanol contamination you will have. Collect until you feel comfortable stopping. It is pretty cool watching a water-like liquid come out of something so thick. The polymer that makes the paint stripper thick will still be in the flask, and depending on how much you took out of it, it will be more or less "hard". I wasn't paying the best of attention :) , and I over collected and the polymer that was left became rock hard.This is very difficult to remove with most solvents including water, alcohols, acetone, acids, etc. Someone on YouTube said that kerosene works well to clean it. I didn't have any on me at the time, so I tried some other methods. I only found 1 method that worked well, but it worked very fast and was good at removing the polymer. I added some concentrated (25-30%) hydrogen peroxide to the flask first, then some sulfuric acid to that. It bubbled quite a bit, and released some smoke, so I wouldn't recommend doing it inside without a fume hood. It almost overflowed the flask with bubbles, but it completely dissolved the polymer within a minute.

There are several methods to purify this product. "mrhomescientist" on YouTube has a good video on purifying DCM. The two main contaminants that would be in it, are water and methanol. To get rid of the methanol, several rinses of water are necessary. Methanol is soluble in water, but DCM is not. Doing several rinses with water will get rid of this contamination. To get rid of the water, you need to put some kind of desiccant in it. Calcium Chloride would probably be the best. Let it dry over that for a while. Then, if you really want pure stuff, you can re-distill the DCM over Calcium Chloride. For most purposes you probably don't need to do this, but it never hurts.  Make sure you dispose of the waste properly, and enjoy your Dichloromethane.