Extraction of Benzoic Acid

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Introduction
The purpose of this experiment is to practice common organic laboratory techniques inside the lab to get one oriented to the basic methods of procedure that can be used for later experiments. This experiment involves the separation of benzoic acid from a more crude form, consisting of benzoic acid, methyl orange, a common acid/base indicator, and cellulose, a natural polymer of glucose (Huston, and Liu 17-24). The technique that is used to perform this separation is called extraction. Extraction is a systematic process of separating mixtures of compounds, taking advantage of the affinity differences of compounds to separate them (Padias 128-37). This technique recognizes the principle that “like dissolves in like,” that is, polar solutes dissolve in polar solvents and non-polar solutes dissolve in non-polar solvents. Through extension of this principle, one can use extraction to separate compounds of a mixture. There are three different methods of extraction; solid-liquid extraction, liquid-liquid extraction, and chemically active extraction. Solid-liquid extraction is used when a desired compound, in a solid phased mixture, has both a water-soluble component and a water-insoluble component. This type of extraction pulls one or more compounds out of the solid mixture into a solvent of the same polarity (Padias 128-37), leaving behind the compounds that are un-soluble. The method is started by placing a mixture of solid compounds into a container and adding either a liquid non-polar solvent, such as diethyl ether, or a liquid polar solvent, such as acetic acid, to dissolve solutes of the solid mixture. Because “like dissolves in like,” the desired solute is dissolved into the solvent and the undesired solute is left in the solid phase. Through use of vacuum filtration, the solid and liquid can be separated, leaving the solid on the filter paper and the liquid in the container below. Liquid-liquid extraction is a method based on the varying...
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