On Wed, 04 Dec 2013 17:44:40 -0500, Fred McKenzie wrote:

According to the dealer where I bought it, the rats eat it but
do not die right away. They become thirsty and have to go outside
to find water. The poison kills them when they drink, so they die outside.

Hmmmm.... I didn't read that, but I wasn't looking for that description
when I looked up the ten registered rodenticides.

Based on this PDF: http://npic.orst.edu/factsheets/rodenticides.pdf

These are the multi-dose anti-coagulants:
warfarin, chlorophacinone, and diphacinone

These are the single-dose anti-coagulants:
brodifacoum, bromadiolone, and difethialone

This makes the brain swell until the rodent dies:
bromethalin

This is vitamin D3 which basically poisons them with calcium:
cholecalciferol

This causes muscle spasms which interfere with breathing:
strychnine

This turns into a deadly internal gas in the presence of acidic water:
zinc phosphide

Given that, I'm guessing your dealer is likely talking about zinc phosphide.
I looked at the symptoms for humans, and there's no mention of thirst though.

I looked a bit at the Wikipedia for rodenticides:
http://en.wikipedia.org/wiki/Rodenticide

It mentions that Zinc Phosphide makes rats die outside, but, it doesn't
mention thirst or drinking water at all. Anyway, the body is full of water,
so, it would work in the stomach anyway (which has HCL & water inside).