Recrystallization

Recrystallization - toluic acid is an irritant and toxic by...

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Recrystallization and Melting Point Determination In this lab, we were given an unknown substance and purified it by recrystallization. To do this, an impure solid was dissolved into hot water. Gravity filtration removed insoluble contaminants through filter paper. The solution was cooled to permit crystallization and water was removed from the crystals by suction filtration. We then took the crystals and determined the melting point using a Digital Melting Point Apparatus. We were able to confirm the melting point of the unknown by mixing it with a known substance and finding the mixed melting point. The unknowns were all organic flammable solids. Acetanilide is an irriant. Benzoic acid is an irritant and toxic by ingestion. P-toluene sulfonamide is an irritant. O-
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Unformatted text preview: toluic acid is an irritant and toxic by ingestion. Salicylic acid is toxic by ingestion. To dispose of the unknowns, we placed them in the “Waste Experiment 2 Crystals” beaker. Also in this lab, we dealt with Bunsen burners to heat up the solutions. I was given unknown number 272. The mass of the unknown was 1.390 grams. After it was crystallized, the weight of the crystals was .91 grams. This gave me a percent recovery of 65.47%. From the Digital Melting Point Apparatus, I approximated my melting point to be 102 ° C. The melting point of o-Toluic acid is between 100 ° C and 106 ° C. I then found a mixed melting point between my unknown and o-Toluic acid at 100 ° C. I concluded that my unknown was o-Toluic acid....
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This note was uploaded on 08/15/2008 for the course CHM U212 taught by Professor Witten during the Fall '08 term at Northeastern.

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