According to this CZ post there are different grades.

//www.curezone.org/forums/fm.asp?i=898281


Here are the grades of Lugols, as per the above link:

Chemical Grade Definitions
Chemical grade definitions from highest to lowest purity...
1. A.C.S.

A chemical grade of highest purity and meets or exceeds purity standards set by American Chemical Society (ACS).

2. Reagent

High purity generally equal to A.C.S. grade and suitable for use in many laboratory and analytical applications.

3. U.S.P.

A chemical grade of sufficient purity to meet or exceed requirements of the U.S. Pharmacopeia (USP); acceptable for food, drug, or medicinal use; may be used for most laboratory purposes.

4. N.F.

A grade of sufficient purity to meet or exceed requirements of the National Formulary (NF).

5. Lab

A chemical grade of relatively high quality with exact levels of impurities unknown; usually pure enough for educational applications. Not pure enough to be offered for food, drug, or medicinal use of any kind.

6. Purified

Also called pure or practical grade, and indicates good quality chemicals meeting no official standard; can be used in most cases for educational applications. Not pure enough to be offered for food, drug, or medicinal use of any kind.

7. Technical

Good quality chemical grade used for commercial and industrial purposes. Not pure enough to be offered for food, drug, or medicinal use of any kind.