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  • 1 Faculty of Technology and Metallurgy University of Belgrade Belgrade Yugoslavia
  • 2 Institute of General and Inorganic Chemistry of The Academy of Sciences of BSSR Minsk USSR
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The iso- and non-isothermal transformations taking place on the heating of LiH2PO4, Li2HPO4, Li5P3O10·5H2O, mixtures of LiH2PO4+2Li2HPO4 and LiH2PO4+Li4P2O7(l) in vacuum, air and water vapour atmospheres at 20–1050° were studied using TG, DTG, DSC, DTA, IR spectroscopy, XRD and TLC analyses. It was shown that solid-phase interaction of the mixture components with the general ratio Li ∶ P ≈ 5 ∶ 3, in contrast to the interaction of analogous sodium (potassium) phosphate mixture components, does not lead to the quantitative formation of anhydrous triphosphate. This is explained by the high crystallization rate of lithium pyrophosphate, which, due to its low reactivity, does not participate in further anion condensation. The increase of triphosphate yield is promoted by the liquid phase formed on disproportionation of acid salts, on melting of reaction components or as a result of introduction of urea additive.