Here are some helpful links:
kemiko.com
amesresearch.com
ultraquietfloors.com/acid_stain.asp
I don’t know why but it seems that there are two products that are referred to as stain. One sits on the surface while the other reacts with the limestone in the concrete and is acid based.
There is a supplier on W. Marginal south of the bridge called Evergreen Supply that has a broad supply of concrete related products and a very knowledgable, helpful staff.