I read some of those posts as well, however at this point I will trust the manufacturer that it truly is ACS purity which is at least 95% which is good enough. I will be testing it, not from a lab, but still need some verification. I also needed it this week and shipping was slower for the AR!
"ACS grade meets or exceeds purity standards set by the
American Chemical Society (ACS). This grade is acceptable for food, drug, or medicinal use and can be used for ACS applications or for general procedures that require stringent quality specifications and a purity of
≥95%." Source:
https://www.labmanager.com/business...common-grades-for-chemicals-and-reagents-2655
It appears that
AR (Analytical-Reagent) can be as high as
99.9%, however the grade (percent of purity).