If you are not part of the solution, you are part of the precipitate

If you are not part of the solution, you are part of the precipitate

This is a chemistry joke. The humor for this joke is derived from a adulteration of a common english phrase: "if you are not part of the solution you are part of the problem", which means the same as "If you are not with us you are against us".

The change from problem to precipitate is interesting, because it invokes the chemistry phenomenon "precipitation", which is when a solid substance is formed from a solution. Thus, in this joke, the word solution is also a pun.

I like this joke - it seems pretty funny.