title: Occurrence of nitrogenous species in precipitated B-type carbonated hydroxyapatites.
abstract: B-type carbonated hydroxyapatites, prepared in aqueous media free of alkali ions, fix ammonium ions present in the reaction medium. A small portion of the carbonate ions introduced into the apatite structure enter by the substitution mechanism (CO3(2-), NH4+)----(PO4(3-), Ca2+). With these results for the structural incorporation of ammonium ions, differences in lattice parameters observed among specimens with the same degree of carbonation were attributed to some substitution of NH4+ for Ca2+. The fixed ammonium ions were shown to be the source of the cyanamide and cyanate ions that develop on heating. Above 500 degrees C these apatites lost both the carbonate and the cyanate and cyanamide ions.
mesh_terms: D002254:Carbonates / Q000032:analysis*; D011232:Chemical Precipitation; D003484:Cyanamide / Q000032:analysis; D003485:Cyanates / Q000032:analysis; D017886:Durapatite; D006882:Hydroxyapatites / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D013055:Spectrophotometry, Infrared; D013818:Thermogravimetry; D014961:X-Ray Diffraction
chemical_list: D002254:Carbonates; D003485:Cyanates; D006882:Hydroxyapatites; D000644:Quaternary Ammonium Compounds; D003484:Cyanamide; D017886:Durapatite; D009584:Nitrogen