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Proceedings Paper

Chemical Composition Determination Of Francolite Apatites By Fourier Transform Infrared (FTIR) Spectroscopy
Author(s): Robin M. Scheib; Raymond D. Thrasher; James R. Lehr
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Paper Abstract

Prior work by Lehr and McClellan and Lehr, based on chemical, crystallographic, and x-ray diffraction studies, showed the relationship between phosphate (P) and substituted carbonate (C) in francolite apatite to be P+C = 6.00 ± 0.04 and the generalized apatite formula to be (Ca,Na,Mg) 10(PO4)6-x(CO3)xFy(F,OH)2, in which y ranges from 0.33x to 0.5x. Using the FTIR, the ratio of the area of the absorption curve for C-0 (bands in the region 1375 to 1550 cm-1) versus the area of the absorption curve for P-0 (bands in the region 530 to 690 cm-1), the "CO2 index," was found to be proportional to the mole ratio of CO3:PO4 in francolites. Stripping methods allowed the subtraction of spectral contributions of silicate and carbonate minerals and water, which would ordinarily interfere with such a determination. The study was based on 65 mineral samples and the formula was found to be: CO2 index = 0.0678 + 4.184(mole ratio CO3:PO4) (1) The correlation factor, r2, was 0.938 and the standard error of the slope ±0.136. The probability of the null hypothesis for the model was less than 0.0001.

Paper Details

Date Published: 29 October 1981
PDF: 3 pages
Proc. SPIE 0289, 1981 Intl Conf on Fourier Transform Infrared Spectroscopy, (29 October 1981); doi: 10.1117/12.932197
Show Author Affiliations
Robin M. Scheib, National Fertilizer Development Center (United States)
Raymond D. Thrasher, National Fertilizer Development Center (United States)
James R. Lehr, National Fertilizer Development Center (United States)


Published in SPIE Proceedings Vol. 0289:
1981 Intl Conf on Fourier Transform Infrared Spectroscopy
Hajime Sakai, Editor(s)

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