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ACS vs. Reagent Grade

Is there a difference between ACS Reagent grade chemicals and Reagent grade chemicals?

The ACS Reagent grade designation indicates compliance with specifications found in the most recent edition of Reagent Chemicals published by the American Chemical Society. Currently, that designation applies to 430 reagents. Each of these reagents must meet all of the specifications described in the reagent monograph in order to be labeled ACS Reagent grade. As an example: The ACS monograph for hydrochloric acid specifies an assay range of 36.5 – 38.0% by weight. If the concentration of the hydrochloric acid is less than 36.5%, it can’t be called ACS Reagent grade. However, if the concentration is 36.5%, but the free chlorine (another specification) is greater than 1ppm, it can’t be called ACS Reagent grade either. Every single one of the 12 specifications listed in the ACS monograph for hydrochloric acid must be met in order to label the product ACS Reagent grade. Puritan Products brand materials that meet ACS Reagent grade are manufactured and marketed as ChemPUR® ACS Reagents.

The Reagent grade designation is used to describe high purity chemicals for which no established specifications exist. Very often these products are solutions of or dilutions of ACS Reagent materials. In the case of sodium hydroxide, only the solid material can carry the ACS Reagent designation. A solution of 50% sodium hydroxide in water can’t be labelled ACS Reagent. Reagent grade chemicals can also be products that require fewer specifications than those shown in an ACS monograph. Going back to our hydrochloric acid example, some of our customers have decided that the assay, color, heavy metals, and free chlorine are the only parameters that affect their work process. They don’t care about the other 8 parameters listed in the ACS monograph, so they are more than happy to buy a Reagent grade product. Puritan Products brand materials that meet the Reagent grade are called ChemPUR® Reagents.

Are ACS Reagent grade chemicals better than Reagent grade chemicals?

The answer to this question is: not necessarily. As we explained above, in order to be labelled an ACS Reagent grade chemical, there must be a monograph for the chemical in the latest edition of Reagent Chemicals, and the chemical must meet all of the specifications given in the monograph. Let’s assume that someone has been adding relatively small amounts of ACS Reagent grade hydrochloric acid, 36.5-38%, to one of the solutions in their manufacturing process. They are concerned about their employees’ safety and have decided that using a larger amount of a 15% dilution will not impact their process and might lower the risk of a serious injury. We can prepare the 15% dilution of hydrochloric acid using ACS Reagent grade raw material, and still run each of the 12 tests specified in the ACS monograph, but the final product will be called ChemPUR® Reagent grade. In this case, the Reagent grade material has been subjected to the same rigorous testing as the ACS Reagent material would have been, and is equivalent in quality.

Do ACS Reagent grade chemicals cost more than Reagent grade chemicals?

The answer to this question is: sometimes, but not always. There are a lot of factors that must be considered when establishing prices. Chief among these are time and labor. As many Reagent grade products are solutions of a solid in water, obviously, time and labor is required to: weigh out the raw materials; add them to the mixing vessel; mix the materials long enough to ensure complete solubility; cool the solution if necessary; filter the solution if necessary; sample the solution and take it to the lab for analysis; run the analyses required by the product specifications; package the approved product; label the material; and finally, palletize it for shipping. The more ingredients there are and the more specifications need to be met, the more a product will cost.

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