Newport...

'This describes the grades:
ACS Reagent Grade,
CP Grade (Chemically Pure),
USP Grade (USBioAnalyzed)
Molecular Biology Grade


http://www.usbweb.com/category2.asp?cat=bio



The purity of the chemical used is not USP, since they use chemicals to extract the Iodine I would not buy less than USP grade (if available).'
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I just spoke with Ricca...they told me that the Clarkson Lugols ACS Reagent Grade was tested & assayed identically to the USP Grade. In fact, the ACS tests .01 in purity whereas the USP Grade is allowed .05 purity.

The residual chloride & bromide of the ACS Grade was .005 whereas the residual USP Grade was 5 x greater... .028.

When I inquired what the primary difference was between the ACS & the USP, they said that the USP underwent an 'identity test', whereas the ACS did not.

Newport, it sounds as though we may be doing some semantic gymnastics here, eh? What say, ye?