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VISUAL DEMONSPRATION OF THE EXTRACTION THEORY EUGENE W. BLANK Research and Development Dept., Colgate-Palmolive-Peet Co., Jersey City, New Jersey
THE THEORY of separation by extraction is usually introductory to the study of organic chemistry. Gattermannl gives a lucid mathematical treatment of the subject in its practical applications in laboratory work. A visual proof that extraction of a given volume of solution by one large volume of an immiscible solvent IS less a c i e n t than numerous extractions with smaller volumes of the solvent may be demonstrated by extracting 25 ml. of a water solution of methyl red with 25 ml. of ether. The water layer remains markedly red
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1 G A ~ ~ E R M A"The N N , practical methods of organic chemistry." translated by Schober and Babasinian, The Macmillan Co.. New York City, 1921, p. 46.
in color whereas five extractions with 5-ml. portions oi ether yields a practically colorless water layer. The water solution of methyl red is prepared by adding 2 ml. of methyl red indicator solution to 100 ml. of water. The indicator is reddened by the addition of 1 ml. of HC1 (1:1). To prepare the methyl red indicator solution, dissolve 0.2 g. methyl red (para-dimethylaniline-azo-benzene ortho-carboxylic acid) in 500 ml. of alcohol and dilute to one liter with distilled water. Numerous other materials, including iodine, were used in the development of this experiment, but methyl red was the only substance found satisfactory.
