I would be willing to bet it was some sort of industrial concentrated cleaning agent like Purple Power.
Guys, always wear goggles with RUBBER seals - NEVER FOAM. The foam will absorb the chemical agent. Rub petroleum jelly around the seals in order to keep out chemical agents. Carry a LARGE bottle of water at all times, and if you believe you have been hit with acid remove all contaminated clothing items IMMEDIATELY and begin washing the substance off your body. Pack a trauma kit with gauze, a clotting agent like CELOX, bandages, and tourniquets. Might want to consider a full-face gas mask as well. Working surplus examples can be had for as little as $10 - including the Czech model M10M.
They are out to kill and maim us. This is serious. Keep your head on a swivel and your powder dry, boys.