Fractional liquid extraction of vitamins

Claim 1

A PROCESS FOR PURIFYING A MIXTURE OF A VITAMIN A ACTIVE MATERIAL SELECTED FROM THE GROUP CONSISTING OF VITAMIN A ALCOHOL AND ITS ESTERS AND NON-ACTIVE IMPURITIES ASSOCIATED THEREWITH WHICH COMPRISES (1) CONTACTING SAID MIXTURE IN A FIRST MULTI-STAGE EXTRACTION ZONE WITH TWO SUBSTANTIALLY IMMISCIBLE COUNTERCURRENTLY FLOWING LIQUID ORGANIC SOLVENTS WHICH HAVE DIFFERENT SPECIFIC GRAVITIES AND BETWEEN WHICH THE VITAMIN A ACTIVE MATERIAL AND THE NON-ACTIVE IMPURITIES HAVE DIFFERENT DISTRIBUTION COEFFICIENTS, SAID MIXTURE BEING INTRODUCED INTO THE SOLVENT STREAMS AT A POINT APPROXIMATELY MIDWAY BETWEEN THE POINTS OF INTRODUCTION OF TWO SOLVENTS, THE EXTRACTION FACTOR OF SAID VITAMIN A ACTIVE MATERIAL WITH RESPECT TO SAID SOLVENT PAIR IN SAID FIRST EXTRACTION ZONE BEING LESS THAN ONE; (2) WITHDRAWING A FIRST EXTRACT STREAM COMPRISING VITAMIN A ACTIVE MATERIAL IN THE HEAVY SOLVENT AND SEPARATELY WITHDRAWING A SECOND EXTRACT STREAM COMPRISING THE LIGHT SOLVENT AND IMPURITIES; (3) SEPARATING THE HEAVY SOLVENT FROM THE FIRST EXTRACT STREAM TO OBTAIN A FIRST VITAMIN A CONCENTRATE; (4) CONTACTING SAID CONCENTRATE IN A SECOND MULTI-STAGE EXTRACTION ZONE WITH THE SAME TWO SOLVENTS IN COUNTERCURRENT FLOW, SAID CONCENTRATE BEING INTRODUCED INTO THE SOVENT STREAMS AT A POINT APPROXIMATELY MIDWAY BETWEEN THE POINTS OF INTRODUCTION OF THE TWO SOLVENTS, THE EXTRACTION FACTOR OF THE VITAMIN A ACTIVE MATERIAL WITH RESPECT TO THE SOLVENT PAIR IN THE SECOND EXTRACTION ZONE BEING GREATER THAN ONE; (5) WITHDRAWING A THIRD EXTRACT STREAM WHICH COMPRISES VITAMIN A ACTIVE, MATERIAL STREAM WHICH COMPRISES AND A SEPARATE EXTRACT STREAM WHICH COMPRISES THE SAID HEAVY SOLVENT AND IMPURITIES; (6) SEPARATING THE LIGHT SOLVENT FROM SAID THIRD EXTRACT STREAM TO OBTAIN A VITAMIN A CONCENTRATE HAVING A GREATER PERCENTAGE CONTENT OF VITAMIN A ACTIVE MATERIAL THAN THE ORIGINAL FEED.