Crystal Research and Technology
Cryst. Res. Technol. 37 (2002) 1121 - Abstract -

R. Kijkowska, Z. Kowalski, D. Pawlowska-Kozinska, Z. Wzorek

Institute of Inorganic Chemistry and Technology, Crakow University of Technology, Warszawska 24, 31-155 Kraków, Poland

Quantitative Determination of Crystalline Na5P3O10–I (Form-I) in Commercial Tripolyphosphate using X-ray Diffraction Patterns

An x-ray diffraction method (XRD) for quantitative determination of the crystalline Na5P3O10–I (Form-I) in a mixture of Form-I/Form-II was applied for commercial pentasodium tripolyphosphate analysis. The XRD pattern of the Form-I shows the unique non-overlapping 2θ peak at a position of ~ 21.8 deg. and also at ~ 29.0 deg. (Cu radiation). The area (integral of the intensity) under the peaks is proportional to the amount of the Form-I in the mixture covering the range up to 100 wt.%. That enables one to obtain a calibration line and to determine the amount of Form-I in the mixture of Form-I/Form-II and also in commercial pentasodium tripolyphosphate.
Commercial samples with high Form-I concentration, in case they are contaminated with sodium pyrophosphate (Na4P2O7 ), should be diluted with Form-II to bring the concentration of the Form-I below 50 wt.% in the analysed sample.

Keywords: X-ray diffraction, quantitative determination, tripolyphosphate


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