More information/motivation/clarifications/background of the puzzle will be posted later. (Goal is to determine minimum # of engineers needed). Hopefully it's clear.
Follow-up question: What if both unknown substances had the same side-effects, and exactly two pints of beer were spiked?
Edit (December 8th, 2010): As promised, here is some additional information. This problem is a famous one and usually phrased as follows:
"The King has 1000 wines, 1 of which is poisoned. He needs to identify the poisoned wine as soon as possible, and with the least resources, so he hires the protagonist, a Mathematician. The king offers you his expendable servants to help you test which wine is poisoned.The standard solution is the binary representation one. An interesting generalization (that has not been solved yet and quite possibly is a hard problem) can be found here, which essentially asks if "k bottles of wine are poisoned, then what is the new minimum # of servants required?"
The poisoned wine is very potent, so much that one molecule of the wine will cause anyone who drinks it to die. However, it is slow-acting. The nature of the slow-acting poison means that there is only time to test one "drink" per servant. (A drink may be a mixture of any number of wines) (Assume that the King needs to know within an hour, and that any poison in the drink takes an hour to show any symptoms)
What is the minimum amount of servants you would need to identify the poisoned wine?"