Two new dodecahydrate trisodium triphosphates Na 3 MP 3 O 10 · 12H 2 O (M = CO (1), Ni (2)) were synthesized using a wet chemistry route and characterized by X-ray diffraction and FT-IR spectroscopy. They are isotypic, monoclinic (P21/n, Z = 2), with pseudoorthorhombic unit cell parameters ( Å , • ): (a = 14, 9906 (4), b = 9, 1628 (2), c = 14, 6660 (4), β = 90, 098 (2), for (1) and a = 15, 0236 (3), b = 9, 1972 (2), c = 14, 6654 (3), β = 90, 0492 (16) for (2)). Values of R/Rw are 0.0267/0.0738 and 0.0284/0.0907, respectively, for (1) and (2). Both compounds were found to be systematically twinned by 180 • rotation around a. Their frameworks are made by slabs parallel to ab plane, resulting from the cohesion of two kinds of metallic chains. IR spectrum confirms the presence of characteristic bands from P 3 O 10 phosphate group.