On Wed, 16 May 2012 14:41:41 -0500, wrote:

I recall reading about some chemical that gets applied to tree stumps to
make them decay fast. Anyone know what this stuff is?

Normally I dig around them and build a fire on top, but I have one too
close to a building.

Potassium nitrate, commonly called saltpeter. It's an oxidizing agent that
accelerates the rotting (oxidizing) of the stump.

It's also a key ingredient,the oxidizer, in black powder.