It is 25% hydrochloric acid. While it could be used to pickle, it is not the best choice.
The fact that worries me is that you do not know what it is..therefore you must not know that it is volatile, i.e. gives off nasty fumes..
Try the MSDS:
http://www.wmbarr.com/ProductFiles/KSG%20Safer%20Muriatic%20Acid.pdfthen look for something a bit safer for you..