Essay about Extraction of Benzoic Acid

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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,
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The mixture would then create two layers which could be drained and separated. After separating the two layers, an addition of an acid and an organic solvent would change the salt back to its original form, thus creating an aqueous layer and a layer with the organic solvent and the organic compound. Evaporation of the mixture then leads to isolation of the organic compound. This experiment uses all three different methods of extraction. Through these methods, it is expected that a pure sample of benzoic acid can be separated from the crude benzoic acid mixture.

Experimental Approximately 4 g of crude benzoic acid mixture was weighed on a balance and placed in a 125 mL Erlenmeyer flask. 50 mL of diethyl ether was poured into the flask, along with 3 boiling stones. The mixture was heated on a steam bath until the ether boiled. A Buchner funnel was used to separate the filtrate from the solid precipitate by vacuum filtration. The solid was discarded and the filtrate was placed into a 500 mL separatory funnel. 30mL of 1M NaOH was added to the 500 mL separatory funnel and was swirled and vented every 10 seconds until the reaction finished. The aqueous layer was drained into a 250 mL beaker. 30mL of 1M NaOH was added again to the 500 mL separatory funnel and was drained into the same 250mL beaker. The mixture in the beaker was put on ice and was acidified by 50 mL of cooled 6 M HCl. A Buchner funnel was used to collect the solid