Chemical preparation and characterization by X-ray diffraction, IR, and NMR spectroscopies and thermal analysis of a new o-ethylphenylammonium triphosphate [2-C2H5C6H4NH3](3)H2P3O10 are reported. This compound crystallizes in a monoclinic unit cell P2(1)/n with the parameters: a = 17.670(1)Angstrom, b = 8.558(8)Angstrom, c = 20.100(2) Angstrom, beta = 100.39(6)degrees, Z = 4, and V = 2990(4) Angstrom(3). Crystal structure has been solved and refined to R = 0.041 using 6857 independent reflections. In this atomic arrangement, layers built by H2P3O103- groups are developed along (10 - 1) direction. Between these layers are located the o-ethylphenylammonium entities which form hydrogen bonds with some external oxygen atoms of phosphoric groups. (C) 2004 Elsevier Ltd. All rights reserved.