from a post, by Unyquity, explaining different chemical grades:


//www.curezone.org/forums/fm.asp?i=855208#i


Here's the Chemical Grades (in order of purity from highest to lowest). USP is THIRD on the list and it is suitable for food, drug & medicinal the use). The two grades that are even BETTER and MORE pure than USP grade are ACS & Reagent (so of course, they too are suitable for food, drug & medicinal use...only more so :)

Therefore, if something is made from ACS or Reagent Grade chemical it is MORE pure than USP chemicals.

Unyquity

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.

laboratory grade is not meant for human consumption. probably made with cheaper KI with a higher pb content.