CALCIUM TELLURATE, CATEO4

Description

Calcium tellurate has the molecular formula of CaTeO4 and the molecular weight of 231.68 grams per mole. Its CAS number is 712354-41-1 and its solubility in water is 0.727 g/100 ml at 20°C. It can be prepared by the solid-state reaction of TeO3 and CaO:
CaO + TeO3 + heat ? CaTeO4
TeO3 melts at 430 °C and a temperature of 600° C serves to drive the reaction to completion. This is the tetragonal meta-tellurate composition. It can also be formed in the same manner by solid-state reaction of telluric acid:
CaO(solid)+H2TeO4(solid) ? CaTeO4(solid)+H2O(gas)
This is also tetragonal in structure, with the meta-tellurate configuration. Of the two possible configurations, the meta-tellurate is said to be the most stable. Telluric acid is soluble in water and produces Te(OH)4O2 anions in solutions.

The Uses of CALCIUM TELLURATE, CATEO4

Calcium tellurate has been used to isolate telluric acid by heating TeO2 with and excess of CaO at 975°C in air at a ration of 1:5 equivalents. The dioxide was completely oxidizedandtheproductwasCaTeO4.Ratiosless thanthis affected the overall yield. By adding nitric acid, soluble calcium nitrate and insoluble telluric acid were formed:
5CaO(solid) + TeO2(solid) + heat?CaTeO4(solid)
CaTeO4(solid) +HNO3(aq)?Ca(NO3)2(aq) +H2TeO4(solid)
If calcium tellurite(IV) is heated, in N2 atmosphere, with stoichiometric amounts of CaO, the reaction product, proceeding at 380–620°C, contained orthotellurate and telluride anions formed in disproportionation:
3CaTeO3 + CaO + heat?CaTeO4 + 2CaTe
The scientific literature concerning calcium tellurate is exceedingly limited and no data on its physical properties have been published. It has found little usage in industry but is available commercially in small quantities for use in research.