[Flash Walken]

Originally Posted by Boo Radley

Gale mentioned he was working with benzodiazepine precursors. (Just in case: Benzodiazepines are a class of drugs, valium for instance).

When explaining to Gus, Gale compared his current experiment to preparing a saturated solution of salt for recrystallization. This is a convenient way to purify a chemical especially on a larger scale. He is likely developing a method to purify the intermediates by recrystallization that will allow him to scale up the synthesis of a drug (or designer drug) while achieving high purity.

At the end of his conversation with Gus, Gale mentions that "this is his work". His area of research might be in drug design and this would be a perfect cover.
If I remember from Breaking Bad, Gus helped Gale with his education so that might also be a reason Gale wants to return the favor.