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NOTES Synthesis of Carbonato-apatitel BY LUISA. R O M O ~
Vol. 76
5?% in excess of the stoichiometric proportion) enough 2 N
h a O H is added to make the suspension 0.50 N with respect to the concentration of NaOH. Then the flask is sealed with a rubber stopper provided with a glass tubing, shaken RECEIVED MARCH13, 1954 intermittently for 5 minutes and digested on the hot plate A considerable amount of work has been done on a t 90' overnight. Following this, the solid phase is washed by centrifuging 5 times with distilled water and twice with the synthesis of hydroxy- and fluoro-apatites both ethyl alcohol. Tests for alkalinity failed to give a pink color in dry systems a t high t e m p e r a t ~ r e ~and - ~ by pre- with phenolphthalein indicating that all the excess of base cipitation reactions6 More recently, the synthesis has been removed. Finally, the alkali-free solid phase was of carbonato apatites by solid state reactions a t dried $t 110' and then heated for 2 hours at a temperature of 300 high temperature has been reported. Characterization.-Firstly, an X-ray spectrogram of a Carbonato-apatite is structurally an apatite finely powdered specimen of a natural apatite" was taken which has (COa=) groups substituted for (OH--)using the G.E. X-ray recording spectrometer with a Cu Ka target and a nickel filter. The d spacings were obtained groups in the crystal lattice. standard tables, and the intensities corrected for backThe occurrence of carbonato-apatite as a consti- from ground (Table I). A spectrogram of the synthetic material tuent of bones has been previously suggested by showed d spacings similar to those obtained with the natPrien.' However, the investigations of Dalle- ural apatite. However, the intensities of the reflections magne, et al.,8 indicate that this compound is not a varied considerably. Samples of the synthetic material a t 300" for 2 hours gave patterns which had the same constituent of bones. They found that acids at- dheated spacings with the intensities of the reflections very similar tack the carbonate leaving the phosphate intact. to those obtained with the natural apatite (Table I).
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Also, it has been reported that carbonato-apatite is one of the forms of phosphates found in alkaline soils.y. lo In this paper are presented the results of an investigation carried out to synthesize a carbonatoapatite from suspension a t relatively low temperature.
Synthesis.-The synthesis of carbonato-apatite was carried out in the presence of an excess of alkali according to the reaction 10CaCOs 6KH2P0, 1 2 0 H - ----f Calo(POa)&Os 6 K + 9COs12H20 The final procedure evolved from a series of investigations is as follows. One gram of CaCOl C.P. grade is placed into a 250-ml. erlenmeyer flask which contains 10 ml. of water. After the addition of 60 t n l . of 0 20 If I(H2PO4 (which is about
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ern.-'.
V
H YDROX Y-APAT I TE (NATURAL)
J I
TITES~
Hydroxy-apatite 3 . 8 6 6 ( 2 . 8), 3 . 4 2 6 ( 4 . 3 ) , 3 . 1 5 3 ( 3 . 2 ) , 3 0.58(2.0), 2 . 7 9 6 ( 1 0 . 0 ) 2 . 7 7 1 ( G . 5 ) ,2 0 9 8 ( 5 . 0 ) , 2 . 6 1 5 ( 3 . 0 ) , 2 . 2 4 8 ( 2 . , 5 ) , 2 , 1 4 1 ( 1 . O ) 1 0 6 8 ( 0 . 5 ) , 1
