Chromatography and Household Cleaning Whoever writes the TV ads for some of t h e currently popular floor cleaners has not done any chromatography experiments lately. To prove this point, let's compare paper chromatagraphy with the act of cleaning a tile or linoleum floar. The spot applied to the paper corresponds to dirt on the floor and the chromatagram solvent t o the liquid eleaner used on the floor, Camera, action! A comely housewife applies the touted product to the dirt on the floar either directly from the container or with a device which spreads the liquid over the floor. The enriched solution or colloid (dirt in the product) is now spread out evenly over the entire floor surface and allowed to dry. The net result is a smooth homogeneous surface of now nice-looking dirt. Meanwhile hack in the laboratory our chromatogram solvent is creeping up the paper. No contact between spat or solvent is made until the liquid has climbed well above its original level a t the bottom of the container. The hulk of the solvent in the container is uncontaminated by the spot and continually supplies fresh solvent to "wash" the spot u p and away from its original resting place. Can the techniques of chromatography be used to improve home cleaning? Yes, unless you are willing t o settle for just spreading the dirt around. Reconsider cleaning a dirty floor with a mop. The mop is soaked in the cleaning solution and moved about over the dirty surface. The dirt is loosened but where does it end up? Partly in the mop but some will remain on the floor in "equilibrium" with the dirt in the mop. The dirty mop is now dipped in the bucket of cleanser to set up a second "dirty equilibrium" which in turn generates a third when the wet mop is applied to new dirty floor area. And so o n . . A superior procedure is to apply the cleaning solution directly to the dirt which will become loosened. A clean, dry mop is used to attract the dirty solution or colloid away from the floor and into the strands by absorption. No equilihrium is established for the flow is unidirectional, as in chromatography. The dirty mop should never be dipped into the bucket of cleaningsolution but rather rinsed and squeezed dry for more absorption work on the floar. Let us look at a second example of dirt removal which can he improved greatly by chromatographic procedures. Suppose you spill a drop of catsup or pea soup an your best shirt. A helpful but chromatographically naive neighbor will immediately administer first aid by applying a damp cloth ta the spot and smearing it all about. Very little of the misplaced soup or condiment will be transferred to the damp cloth for the flow is more likely to he in the opposite direction, into the shirt itself. Admittedly the shirt will look a little better but the dirt has just been diluted and spread over a larger area; however it is still in the garment. A chromatographer takes a different approach in eliminating the spot. The fint step is to remove as much as possible of the food with a spoon or table knife, for a n overloaded chromatogram is seldom efficacious. A dry cloth is placed directly over the spot, thus counteracting the flow of dirt into the shirt. Finally a damp cloth is placed on the reverse side of the garment under the spot so that clean solvent now flows through the fabric taking the dirt with it into the dry absorbing cloth, a process very similar to chromatography.
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Thomas MeCullough, CSC St. Edward's University Austin, Texas 78704
830 /Journal of Chemical Education
