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potent substance was then separated from the aqueous solution by filtering or by centrifuging and when separated was washed with a saturated aqueous solution of benzoic acid to free it from any ammonium sulphate solution still adhering to it. 95% alcohol was then added to the washed precipitate to dissolve the benzoic acid and potent substance and in sufficient quantity to make a concentration of 80% alcohol. This alcohol solution was stirred or agitated and then allowed to stand so that any inert material could settle after which it was filtered. After filtration the major portion of the alcohol was boiled off from the filtrate which was then shaken with ether and water and allowed to stand when two layers were manifested. The lower aqueous layer contained the potent substance in concentrated and purified form and the upper layer contained the benzoic acid. The lower aqueous layer was separated from the mixture and washed with ether to remove any remaining traces of alcohol and benzoic acid after which the traces of ether waer boiled off. The acqueous residue was then sterilised by filtration through a Berkfeldt filter and contained the potent substance.