The purity ratings are not necessarily ordered in speriority, but if I had to do it anyway, it'd be something like this: crude < technical < purified < photographic < pharmaceutical < analytical reagent

Today, it often happens that technical, purified and photographic are very similar or same. But for many agents there is ANSI standard for photographic grade chemicals. Pharmaceutical grade is not necessarily all that pure but they have different set of requirements, as you might have guessed. Analytical grades are made with special attention in purity, and they must be tested for purity at the time of packaging and certified. That is, if someone repackage an agent rated at AR grade, it is no longer AR grade, unless it is re-tested and pass it. It's very strict.

Some chemical companies claim they sell reagent grade chemicals, but they sent me chemicals contaminated with insoluble crap, etc. Triple-S Chemical Products, Inc. is one of them. They sent me certificate of analysis, which says that their chemicals are ACS AR grade, but the stuff is obviously crap, for the insoluble matter alone. I could get much purer technical grade chemicals elsewhere.