You've run into the barely mentioned copy protection.

When you're in the laboratory and have to mix the stuff, the printed game manual would have told you to mix it in (I believe, I could be wrong, doing this from memory) a 4-1-2 ratio.
Anything else and you eventually die.
Give it a shot. If 4-1-2 is wrong, give it a google, I saw it on a forum out there somewhere, just don't remember where.
- Shaid