Solid zirconium arsenates

Karyakin et al. [98KAR/CHE] studied the enthalpy of formation of unhydrated two forms of zirconium arsenate, a-Zr(HAs04)2 and p-Zr(HAs04)2 as well as hydrated zirconium arsenate, Zr(HAs04)2 H20(cr), using adiabatic calorimetry. The enthalpy data obtained by these workers are  

These values are selected by this review. The uncertainties for P-Zr(HAs04)2 and the hydrated solid are the unweighted average from the determinations of the enthalpy following four separate reaction schemes the uncertainty covers the range in the 95% interval of the four separate determinations. 

There are no other reported thermochemical data for zirconium arsenate compounds. 

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Of the 80 or so scarce elements, many occur in solid solution in major rock-forming minerals (e.g., rubidium, strontium, vanadium, germanium, gallium, scandium, rare earth elements (REEs)), or in solid solution in widely distributed, refractory, or low-solubility accessory phases (e.g., hafnium). Some elements, such as zirconium and phosphorus, form their own minerals. Others, like the base metals (e.g., copper, lead, zinc), semi-metals (arsenic, antimony, bismuth), and... 

These authors studied the enthalpy of dehydration of zirconium phosphate and arsenate, in the temperature range 95 to 140°C and 90 to 110°C, respectively, by measuring the partial pressure of water vapour over the solid phases using a tensimetric method. The reaction studied was ... 

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