Methylsulfuric acid potassium salt is primarily used as a reagent in organic synthesis, particularly in methylation reactions. It serves as a methylating agent, introducing methyl groups into various organic compounds, which is essential in the production of pharmaceuticals, agrochemicals, and specialty chemicals. Additionally, it finds application in the preparation of esters and ethers, contributing to the development of polymers and surfactants. Its role in facilitating specific chemical transformations makes it valuable in research and industrial processes.