Chemical preparation, calorimetric studies, crystal structure and spectroscopic investigations are given for a new noncentrosymmetric organic cation monophosphate [2, 5-(CH3) 2C6H3NH3] H2PO4. This compound is orthorhombic P212121 with the following unit-cell parameters: a= 5.872 (4), b= 20.984 (3), c= 8.465 (1) Å, Z= 4, V= 1043.0 (5) Å3 and Dx= 1.396 gcm− 3. Crystal structure has been solved and refined to R= 0.048 using 2526 ...