Chemical preparation, x-ray single crystal, and thermal analysis of C6H18N2SO4. H2O (denoted DMPS) are described. The compound crystallizes in the triclinic system with P (1) over bar space group. Its unit cell dimensions are a = 5.826(1) Angstrom, b = 10.014(1) Angstrom, c = 11.221(1) Angstrom, alpha = 66.716(1)degrees beta = 84.395(1)degrees, gamma = 83.759(1)degrees, V = 596.7(1) Angstrom(3), and Z = 2. The DMPS structure is built up from inorganic chains parallel to the a axis and linked via O(W)-H ... O hydrogen bonds. These chains are interconnected by organic groups. Thermal analysis reveals the presence of one water molecule in the structure and shows a reversible weak phase transition.