Methanesulfonic acid (MSA) is a strong organic acid with the chemical formula CH3SO3H. It is also known as methylsulfonic acid. MSA is derived from methane, where one of the hydrogen atoms is replaced by a sulfonic acid group (SO3H). It is a colorless, viscous liquid that is soluble in water and many organic solvents.

MSA is widely used in various industries and applications. Here are a few examples:

1. Chemical Synthesis: MSA is commonly used as a catalyst or acid catalyst in organic synthesis reactions. It can promote esterifications, etherifications, and other acid-catalyzed reactions.

2. Electroplating: MSA is employed as an electrolyte additive in the electroplating industry. It helps improve the quality and smoothness of metal plating, particularly in the case of gold and silver.

3. Pharmaceuticals: MSA is utilized in the synthesis of certain pharmaceuticals and active pharmaceutical ingredients (APIs). It can be employed as a reagent or acid catalyst during drug development.

4. Polymer Industry: MSA is used as a polymerization and esterification catalyst in the production of various polymers, such as polyester resins, polyurethanes, and sulfonate polymers.

5. Cleaning Products: MSA can be found in some cleaning products, especially those designed for removing mineral deposits, rust, and hard water stains. It acts as a strong acid to dissolve and remove these stubborn stains.