I suspect that would be sodium nitrate you mean. It has been commonly used to keep fresh red meat/hamburger from turning brown (but the meat oxidizes anyway).

My dad used to smoke 2-pound carp in a home-made cold smoker....mebbe 20 at a time in an over-turned 40" x 48" x 40" fiberglass chamber. That damn smoked fish was a beer drinker's dream I tell ya!

I've only smoked turkeys for the most part. I need to get back to that mode!