Thermogravimetry and differential thermal analysis studies on potassium titanyl oxalate and potassium aluminium oxalate and related oxalates

Abstract

Thermogravimetry and differential thermal analysis studies are reported for potassium titanyl oxalate, potassium aluminium oxalate and the related oxalates, potassium, titanyl and aluminium oxalates. The thermal decomposition of these materials in dynamic atmospheres of air, nitrogen and carbon dioxide has been studied. The oxalates and their decomposition products have been characterised by chemical and X-ray analysis. The thermal decomposition results for the complex oxalates show distinct reaction stages, but the aluminium and titanyl oxalates are not clearly characterised under the conditions used in the present work.

The dehydration of the potassium titanyl oxalate starts at 70° C and proceeds in several stages until completion at 200° C. The anhydrous oxalate is not stable although only 1 per cent. of the original weight is lost between 200° and 275° C, but the decomposition is rapid above 275° C. The titanate formed as the final product is the result of the initial decomposition of the anhydrous complex. Potassium aluminium oxalate gives a stable anhydrous complex over the range 150° to 375° C, followed by a two-stage decomposition, with the bulk of the reaction complete at 575° C, and the end product is potassium aluminate, formed as a result of the initial decomposition.