A series of B-type carbonate apatites have been prepared by the "direct" method and their structural properties investigated. The standard molar enthalpy of formation have been determined from enthalpy of solution measured by calorimetric technique. Statistical treatment of thermochemical results shows that the most probable substitutions in this kind of products are couple substitutions (CO3, OH) for PO4 and (2 CO3, V-Ca) for 2 PO4. (C) 2010 Elsevier B.V. All rights reserved.