second run is with a mixture comprising 80 methyl benzoate 20 salicylic acid this agent gives a relative volatility of 1 34 which compares with 1 26 and 1 25 shown in table 1 the third run is with methyl salicylate which gave an average relative volatility of 1 27 after two hours of steady operation this can be compared with 1 22 and 1 28 shown in table 1 the usefulness or utility of this invention can be demonstrated by referring to the data presented in table 1 2 and 3 all of the successful extractive distillation agents show that ethanol can be removed from t butanol by means of distillation in a rectification column and that the ease of separation as measured by relative volatility is considerable without these extractive distillation agents virtually no improvement will occur in the rectification column the data also show that the most attractive agents will operate at a boilup rate low enough to make this a useful and efficient method of recovering high purity ethanol from any mixture with t butanol the stability of the compounds used and the boiling point difference is such that complete recovery and recycle is obtainable by a simple distillation and the amount required for make up is small twenty five grams of ethanol 25 grams of t butanol and fifty grams of methyl benzoate were charged to an othmer type glass vapor liquid equilibrium still and refluxed for five hours analysis of the.