${\mathrm{BeC}}_2{\mathrm{O}}_4$ and ${\mathrm{BaC}}_2{\mathrm{O}}_4$  are heated separately with Bunsen burner. The solid residue obtained are respectively:

The compound beryllium oxalate trihydrate decomposes on heat treatment to beryllium oxide.

There was some indication of intermediate compounds existing in the decomposition of the BeO.

By decomposing the beryllium oxalates at various temperatures, the surface area of the solid residue increases with a loss of crystal morphology.

The following reaction is obtained when ${\mathrm{BeC}}_2{\mathrm{O}}_4$ and ${\mathrm{BaC}}_2{\mathrm{O}}_4$ are heated, 

$\begin{array}{l}{\mathrm{BeC}}_2{\mathrm{O}}_4\stackrel{\mathrm{\Delta }}{\to }\mathrm{BeO}+\mathrm{CO}\\ {\mathrm{BaC}}_2{\mathrm{O}}_4\stackrel{\mathrm{\Delta }}{\to }{\mathrm{BaCO}}_3+\mathrm{CO}\end{array}$

Hence BeO and ${\mathrm{BaCO}}_3$ obtained as the result when  ${\mathrm{BeC}}_2{\mathrm{O}}_4$ and ${\mathrm{BaC}}_2{\mathrm{O}}_4$ are heated separately.