Answer :
There is the commercial-grade, which is 70% strength in water, and it's pretty nasty stuff. It'll chew through your lab coat and give you burns you'll regret, as you'd expect from something that's rather stronger than nitric or sulfuric acid.
But it has other properties. The perchlorate anion is in a high oxidation state, and what goes up, must come down. A rapid drop in oxidation state, as chemists know, is often accompanied by loud noises and flying debris, particularly when the products formed are gaseous and have that pesky urge to expand. If you take the acid up to water-free concentrations, which is most highly not recommended, you'll probably want to wear chain mail, because it's tricky stuff. You can even go further and distill out the perchloric anhydride (dichlorine heptoxide) if you have no sense whatsoever. It's a liquid with a boiling point of around 80 C, and I'd like to shake the hand of whoever determined that property, assuming he has one left.
