Alchemy bug?

[AbsoluteMonkey]

Someone suggested I post this bug I've been having.

I am trying to use the '2 Lead of Countermagic' recipe.
2 lead
pile of philosophical phosphorus

Put in the ingredients, cast alchemy and my cauldron reacts twice.
First will say 'Your cauldron bubbles'
Then 'Your cauldron produces steam'

And then I have slag in it. I've tried with other recipes and it works fine. But it will always do this wit h this recipe. I've tried it five times now. And I've even tried alternating with water of wise. Still same thing.

Any ideas?