Unfortunately, there is currently no accurate information about the chemical substance with the formula H2Cr4O9. You may have mistyped the formula, or this chemical substance does not exist or has not yet been discovered and named. Please verify the formula you are looking for and ensure it is officially recognized and recorded in reliable chemical information sources. With an accurate chemical formula, we can provide detailed information about the name, molecular structure, physical and chemical properties, as well as related chemical equations and synthesis processes.