Billm302, a good drench to get rid of an ants nest is water, really soak em and keep it moist, they don't like that. They want a place that's dry and undisturbed.
Boric acid baits work better than other poisons on ants, afaik. I have tried spraying with some pyrethrum stuff a few years ago, and they even seemed to get off on it!
Insecticidal soap spray was really slow to have any impact on them, not a very effective way of crushing them..
Hot water and bleach did the job on a nest in a wall...