So... is there any evidence in the "adding chemicals to prevent freezing" claim? I've heard this before, but find it hard to believe.
http://www.yorksnow.com/products/snomax/index.htm
http://www.yorksnow.com/products/snomax/safety.htm has an overall description. It's a biological protein. It's *NOT* a chemical additive. It's a protein that snow 'likes' to form on. And it doesn't prevent anything. It just serves as the the 'dust stuff' that snow forms on naturally.