If you bought it from their swimming pool supplies section, it is not food grade.
Allen Herod wrote:I bought a 20lb bag at Tractor Supply Co. yesterday for my dog. It says "Diatomaceous Earth and Calcium Bentonite, Food Chemical Codex Grade" They carry it as something to mix with animal feed. "95% Ash (mineral matter)" Someone correct me if im wrong, but this is the stuff right? The brand i got is "Red Lake Earth" and made in Canada. My puppy has a touch of mange. Last night I gave her an oatmeal bath and dried her off real good. Then sprinkled the stuff on her and rubbed it in making sure it got up under her coat real well and rubbed it into the one small bald sore spot she has on her head. She sat still while i did it and didn't do any excessive scratching after that (really no more scratching at all) This morning the redness is gone from the bald spot. The 20 lb bag was $12.99.
Sounds right to this chemist. The reason it chemically analyzes out as "95% ash" is that diatomaceous earth is silica particles or SiO2, which is also known as "silica ash". The other 5%? Well, that would cover the calcium and aluminum that might be present from the bentonite.
Nice to know it works on mange, I'll have to file that fact away.