A new organic dihydrogenmonoarsenate (C(3)H(9)N(2)O(2))H(2)AsO(4) (abbreviate as ECAs) is prepared by reacting H(3)AsO(4) with ethyl carbazate. This compound crystallizes in the monoclinic crystal system, space group P2(1)/n. Unit cell parameters are a = 4.8370(2) angstrom, b = 24.6270(2) angstrom, c = 7.6311(5) angstrom, beta = 92.948(4)degrees, with, Z = 4 and rho(m) = 1.800 g cm(-3). The structure is solved, using the direct methods and refined against F(2) to a reliability R factor of 0.0475. The compound is characterized by infinite [H(2)AsO(4)](n)(n-) ribbons, parallel to the a-direction, connected by organic cations and forming layers localized at y = 0 and 1/2. The cohesion of the framework is ensured by hydrogen bonds N(O)-H center dot center dot center dot O. The thermal properties of the compounds are investigated as well as the IR properties supported by group theoretical analyses. (C) 2010 Elsevier Ltd. All rights reserved.