The Countercurrent Extraction of Ink A Demonstration of the Chromatographic Mechanism Clark E. Brickerl and Gregory 1.Slwp Davidson College, Davidson, NC 28036 The importance of multiple extractions in the theorv of separations by chromatography is well known. ~ o w e v & a, simple system that can demonstrate quickly and visibly the significance of discontinuous countercurrent extraction has not been reported and thus students do not generally appre- ciate the value of this technique. In a recent publication,2 a countercurrent distribution experiment was described that required several operations (a 10-tube extraction, evaporation of the solvent layers, reconstituting the solutes, gas-liquid chromatography) before the separation of the two organic compounds that was achieved bv the countercurrent extraction could be realized. There was no immediate visible evidence from the extraction that a separation had been performed. The followinn experiment can be carried out in less than 2 h, and the merits of the countercurrent extraction are immediately evident by the visible colors. This experiment requires eight 125-ml separatory funnels, 250 ml of 1-hutanol (Caution: 1-butanol has a uolatile, explosiue nature), 250 ml of 0.1 to 0.5 M HCI and a small amount of Sheaffer's Skripe blue-black soluble ink. Equilibrate 250 ml of I-butanol with 250 ml of 0.1 to 0.5 M HCI (the acidity of the HC1 is not critical) in a large separatory funnel. Then, transfer 251.111 portions of the 1-butanol layer to each of eight 125-ml separatory funnels. Add 25 ml of the equilibrated aqueous layer to funnel 1and 0.3 ml of Sheaffer's blue-black ink. Shake the separa'tory funnel for 2 min, then allow the layers to separati raint the aqueous layer from flask 1into flask 2, and add a fresh 25-ml aliquot of the equilibrated aqueous layer to flask 1. Shake both separatory funnels for 2 min, and after the layers have separated, drain the bottom or aqueous layer of flask 2 into flask 3 and the bottom layer of flask 1 into flask 2. Again, add a fresh 25-ml portion of the equilibrated aqueous laver to flask 1, and then-shake the three separatorifunnels-for 2 min. Continue this procedure until extractions have been carried out in all eigh
