Hmm. You would describe the smell of vinegar to be rather pungent, correct?

[Colress pulls out several bottles that he gathered during his investigation.]

I had a feeling that some chemicals may have been at play here, so I paid a visit to the chemistry lab. A few bottles from the wall have been nearly emptied since I last took stock: iodine, ammonia, and acetic acid.

The latter may be of importance for this bit.