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Stopper the tube to reduce evaporation mix well by

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acid in the test tube (see figure 2). Stopper the tube to reduce evaporation. Mix well by holding the tube loosely at the top between two fingers and flicking the bottom of the tube with a fingernail. This imparts a swirling motion to the liquid and mixes it without getting the liquid in contact with the stopper. Transfer 1.0 ml (use 1 ml transfer pipet) of this petroleum ether solution to a second test tube; dilute with 9.0 ml of petroleum ether, stopper, and mix well. Transfer 1.0 ml (use a 1 ml transfer pipet rinsed once with pure petroleum ether) of the petroleum ether solution from the second test tube to a third tube; again, dilute with 9.0 ml of petroleum ether, stopper and mix thoroughly. Dust the oil surface in the aluminum pan very lightly with lycopodium powder. The purpose of the lycopodium powder is to make it easier to see the film of oleic acid on the surface of the water. Using a graduated 1 ml pipet, (rinsed once with pure petroleum ether) place exactly 0.10 ml of the third (last) solution of oleic acid in petroleum either on the center of the water surface. Wait five minutes for the petroleum ether to evaporate. Support the glass plate just above the water surface on wooden blocks. Do not let the glass touch the film surface.
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