Magnesium sulfate heptahydrate is a magnesium-containing compound with the molecular formula MgSO4 (or MgSO4 7H2O). Anhydrous magnesium sulfate is a commonly used chemical and drying reagent. However, magnesium sulfate often refers to magnesium sulfate heptahydrate, because it is not easy to deliquescence and is easier to weigh than anhydrous magnesium sulfate, which is convenient for quantitative control in industry.