A 30% aqueous solution of picric acid is neutralized by an addition of concentrated cesium hydroxide solution. The solution is then cooled down in a freezer and filtered to obtain the product. The product may be dried with a desiccator.
(O2N)3C6H2OH + CsOH = C6H2CsN3O7 + H2O
Crystallization of the product from the neutralized solution
The pure product