The washing is continued until the filtrate is free from salts or acids.
The filtrate, on being boiled down, yields a second crop of uranate.
The filtrate, which may be collected in glass vessels if an excess of hydrofluoric acid has been avoided, deposits the greater part of the salt on cooling.
If this be dissolved in water and the solution concentrated, some silicic acid separates and the filtrate deposits triclinic prisms of tungstosilicic acid.
The liquid is filterpressed, and any excess of iron in the filtrate is precipitated by the careful addition of caustic soda and then removed.