A little science history for a grey and brow-wrinkled Friday.

In 1878, one of the pre-eminent national powers experienced one of its greatest economic disasters ever; the solution was discovered 1882 through in a mixture of copper sulfate, quicklime, and water, which had been initially used as a kind of ad-hoc theft deterrent. This mixture became the first commercial example of a now-common category of chemical.

What category of commercial chemical was invented with this mixture?

First correct answer posted to comments wins an annotated copy of Mary Pope Osborne's High Tide in Hawaii (No. 4,036 in the Magic Tree House series). No Googlery or bothering Marilyn Vos Savant at home. The woman has a Parade column to write, for pete's sake!