Tetrahydrocycline is apparently a highly volatile chemical compound.
He brings it forward as a means of posturing, preventing Commander Adama and others in the know from realizing that he has no true means of detecting humanoid Cylons in the Fleet after Galactica's port water tanks are blown open to space, likely by a Cylon saboteur (Water).
- Baltar's medical experience (by way of his panic) may have meant hydroxytetracycline, which is far from a volatile chemical compound on the real-world Earth. The compound is an broad-spectrum antibiotic used to treat a variety of infections, from acne and anthrax to the Plague. Another possibility is Cyclohexene, assuming "cycline" refers to benzene.