Sodium Carbonate is used as a basimetric standard but it is not a very good primary standard since it is difficult to dry, is hygroscopic, and has a relatively low equivalent weight. For these reasons, Tris(hydroxymethyl)aminomethane has largely replaced it as a basimetric standard. Sodium Carbonate is a diequivalent base and it can be assayed by titration with a standard strong acid to the first equivalence point (pH ~ 8.3) using Phenolphthalein Indicator, or to the second equivalence point (pH ~ 3.7) using Methyl Orange Indicator.