ACS Grade chemicals

What the grade means

ACS grade refers to the specifications in Reagent Chemicals, a compendium published by the American Chemical Society. Each monograph sets a minimum assay, maximum impurity limits and the test methods to use. Because the standard is public, an ACS label should mean the same thing whichever producer filled the bottle.

The monographs are revised from time to time, so a COA for ACS material should state that it conforms to the current edition.

Typical specification points

Concentrated hydrochloric acid to ACS, for example, has an assay of 36.5 to 38.0 percent HCl, residue after ignition at or below 5 ppm, sulfate at or below 1 ppm and free chlorine at or below 1 ppm, with low ppm limits for iron and heavy metals.

When to choose it

Choose ACS grade when a method names it, as many US standard and regulatory methods do, or when you need consistent limits across several suppliers. It is also a sensible default for analytical reagents in pharmacopoeial testing, where the pharmacopoeia refers to reagent specifications.

Documentation

Lots ship with a COA reporting each ACS test and a GHS SDS. ACS products are listed in Lab Reagents. Compare with AR grade if cost is a factor.