HIGH PURITY SYNTHETIC CRYOLITE IS PREPARED FROM WET PROCESS PHOSPHORIC ACID SOLUTION THROUGH TREATMENT OF THE SOLUTION WITH AN ALKALI SALT SO AS TO FORM CRYSTALLINE ALKALI FLUOSILICATE, HEATING THE ALKALI FLUOSILICATE THUS OBTAINED WITH CONCENTRATED SULFURIC ACID AND AT LEAST ONE ALKALI SALT SELECTED FROM THE GROUP CONSISTING OF ALKALI CHLORIDE AND ALKALI NITRATE AND ABSORBING THE GAS THEREBY EVOLVED SO AS TO PROVIDE A SOLUTION OF HYDROFLUOSILICIC ACID AND EITHER HYDROCHLORIC OR NITRIC ACID, AND REACTING THIS SOLUTION OF HYDROFLUOSILICIC ACID WITH SODIUM ALUMINATE SOLUTION.