I don't think MDMA freebase is particularly unstable, though it might be volatile. I am indeed talking about the HCl salt, which is what I presume anyone who needs advice on how to dose without a scale has.
As a rule of thumb, like dissolves like. So, non-polar compounds dissolve in non-polar solvents, so MDMA base will dissolve in toluene/xylene/whathaveyou. However, the salt is ionic, and so will dissolve in polar solvents like water. It's important to understand that these aren't discrete and separate categories, solvents have differing degrees of polarity. Acetone has an oxygen molecule double-bonded to a carbon, which makes it more polar than, say, xylene, which only has C-C bonds and C-H bonds, but less polar than water, where the oxygen (very electronegative) is bonded to two hydrogens. In this case, yes, acetone is sufficiently non-polar that it will not dissolve MDMA.HCl.
As a rule of thumb, like dissolves like. So, non-polar compounds dissolve in non-polar solvents, so MDMA base will dissolve in toluene/xylene/whathaveyou. However, the salt is ionic, and so will dissolve in polar solvents like water. It's important to understand that these aren't discrete and separate categories, solvents have differing degrees of polarity. Acetone has an oxygen molecule double-bonded to a carbon, which makes it more polar than, say, xylene, which only has C-C bonds and C-H bonds, but less polar than water, where the oxygen (very electronegative) is bonded to two hydrogens. In this case, yes, acetone is sufficiently non-polar that it will not dissolve MDMA.HCl.
