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  • 1 Department of Chemistry University of Science and Technology Kumasi Ghana
  • | 2 47 Arlesford Road SW9 9JS London England
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The kinetics of strontium tungstate crystallization from sodium tungstate melts in platinum crucibles were studied by differential thermal analysis at crystallization temperaturesT0=800, 900 and 1000° by continuous cooling at ratesRT=40, 120 and 200° per hour. Heterogeneous nuclei that first formed on the metal platinate particles in the solution during the induction periods (t) grew to small crystallites (¯l). The main crystal growth started after the development of some excess solute concentration (Δ¯C) at the end of the induction temperatures (¯T). For the first 80% crystallization, the average crystal lengths (lτ) varied with the growth time (τ) according to the relation where is the diffusion rate constant at temperatures nearT, andM is the metal salt molecular weight. The initial growth rates and the ratioslτ2/τ depended onΔ¯C instead ofRT The last 20% growth was controlled only by the rate of development of the excess solute concentration.

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