Chemical grades
There are many different grades, also know as purities of chemicals. Chemical purity is important in many applications, but most procedures carried out by amateur chemists don't require a specific purity of reagent.
Common reagent grades by locality
United States
ACS Reagent: A reagent that meets or exceeds the specification of the American Chemical Society. ACS reagents are high quality chemicals for lab use. A certificate of analysis or (COA) can be provided by the manufacturer.
Guaranteed Reagent (GR): A reagent that usually meets ACS specifications and is meant for analytical chemistry.
AR: A reagent that is suitable for laboratory use.
Reagent: The highest available purity for a reagent that the American Chemical Society does not have specifications for.
Purified: A chemical of good quality, this is fine for amateur chemistry.
Lab Grade: A reagent suitable for general lab applications.
USP: Meets standards set by the United States Pharmacopeia.
FCC: Chemicals that meet the standards set by the Food Chemical Codex, FCC reagents are food grade.
Technical: Reagents that have not been analyzed or are industrial grade. These may or may not have significant contaminants.
Poland
Cz.: Reagent for general lab usage.
Cz.d.a: Reagent for analysis.
Some things may have no grade, or be mixtures, and thus are 'general use' grade, or 'consumer grade'.
Sources
Reagents: http://www.reagents.com/products/reagents/grades.html
