Process of producing hydrogen fluoride from fluosilicic acid in a two-stage procedure

Claim 1

IN A PROCESS OF PRODUCING HYDROGEN FLUORIDE AS A DRY VAPOR FROM FLUOSILICIC ACID -CONTAINING SOLUTION IN A TWO-STAGE PROCEDURE, THE IMPROVEMENT WHICH COMPRISES SUBJECTING A FLUOSILICIC ACID-CONTAINING SOLUTION TO THE ACTION OF HEATED CONCENTRATED SULFURIC ACID IN A CLOSED REACTOR IN A FIRST STAGE UNDER CONDITIONS OF RELATIVELY HIGH CONCENTRATION OF SULFURIC ACID, RELATIVELY ELEVATED TEMPERATURE AND RELATIVELY SHORT RETENTION TIME SO THAT SUBSTANTIALLY ALL OF THE SILICON TETRAFLUORIDE IS EVOLVED IN THE FIRST STAGE AS A SUBSTANTIALLY DRY VAPOR WHILE MOST OF THE VAPOR OF HYDROGEN FLUORIDE IS RETAINED IN THE REMAINING DILUTED WEAKER SULFURIC ACID SOLUTION, WITHDRAWING SAID VAPOR CONTAINING SILICON TETRAFLUORIDE FROM SAID CLOSED REACTOR IN SAID FIRST STAGE, REMOVING SAID DILUTED WEAKER SULFURIC ACID SOLUTION CONTAINING HYDROGEN FLUORIDE VAPOR FROM SAID CLOSED REACTOR IN THE FIRST STAGE, CONDUCTING SAID REMOVED SOLUTION TO A LARGER CLOSED REACTOR IN A SECOND STAGE, INTRODUCING INTO SADI LARGER CLOSED REACTOR HOT CONCENTRATED SULFURIC ACID SUFFICIENT TO MAINTAIN A TERMINAL CONCENTRATION OF SULFURIC ACID EFFECTIVE TO CAUSE THE LIBERATION OF HYDROGEN FLUORIDE AS A SUBSTANTIALLY DRY VAPOR, CONTROLLING THE TIME OF RETENTION OF SAID SOLUTION IN SAID LARGER REACTOR IN SAID SECOND STAGE TO AN EXTENDED PERIOD TO LIBERATE SUBSTANTIALLY ALL FO THE HYDROGEN FLUORIDE VAPOR FROM SAID SOLUTION, AND WITHDRAWING SAID LIVERATED HYDROGEN FLUORIDE VAPOR FROM SAID LARGER REACTOR IN SAID SECOND STAGE.