Introduction
The purpose of this lab is to purify four solid compounds: resorcinol, anthracene, benzoic acid, and 4-amino 1-napthalenslfonic acid, sodium salt. This is achieved by using water, toluene, and ligroin as solvents. The solubility of the compounds in said solvents must be tested at low and high temperatures. Then, the solution can be recrystallized. Finally, the product is filtered, using either a Pasteur pipette or suction filtration.
Experiment
In the lab, the sand bath was turned on to 40%. A rough estimate of 10 mg of each solid sample is placed in a test tube. This solid was transferred to a test tube sing a disposable pipet. A boiling stick was placed in a reaction tube. Then, 0.25 mL of the solvent was dropped in the tube and flicked. For the compounds that had a solid dissolve at room temperature, nothing else has to be done. When some dissolved, then an extra 0.25 mL is added and reheated. If it is insoluble, then it was attempted to be heated, but will not dissolve. The dissolved compounds must be cooled to see the crystallization. All four compounds were tested in three solvents (water, hexanes, and toluene). Phthalic Acid was weighed to be 54 mg. 0.33 mL of water was supposed to be used, but 0.5 mL was necessary for the solid to dissolve. A boiling stick was placed in the test tube and the solution was brought to a boil. The water was added drop wise until the last solid piece dissolved. The test tube cooled undisturbed. Once it reached room temperature, it was further cooled in an ice bath. When the crystallization was completed, the crystals were stirred with a pipette. Air was expelled from the bottom and solution was drawn up. The test tube was tapped on a soft surface and repeated if any solvent remained. The curved end of the spatula was used to scoop up the remaining solid. The crystals were left overnight before weighing. The recrystallization of benzoin began with weighing 53 mg of the compound. Ten drops of ethanol was added, then boiled for half a minute. Later, more drops were added until all of the solid was dissolved. The approximate amount of solution in the tube was 0.70 mL. The solution was allowed to cool to room temperature, then placed in an ice bath to cool further. The filter flask was clamped to the ring stand using a 3-pronged holder. The plastic Hirsch funnel was placed into the flask. The filter paper was weighed and placed inside the funnel. The vacuum tbing was connected to the side-arm of the flask. A few drops of fresh solvent was added to the funnel. The crystal was rinsed with fresh, chilled solvent. The seal was broken and ten drops of ethanol-water mixture was added, followed by an immediate continuation of the vacuum filtration. The crystals were let to dry overnight before weighing. The contents of the tubes was disposed of in waste containers. Any glassware needed for immediate use had acetone added to clean quickly.
Results
Phthalic Acid 0.485 g 0.485g/0.54g * 100 = 89.8% recovery of Phthalic Acid
Benzoin 0.250 g 0.250g/0.53g * 100 = 47.2 % recovery of Benzoin
Anthracene
Cold (Room Temp.)
Hot (Boiling)
Water
Insoluble
Insoluble
Toluene
Insoluble
Soluble
Hexanes
Insoluble
Slightly Soluble
Benzoic Acid
Cold (Room Temp.)
Hot (Boiling)
Water
Insoluble
Slightly soluble(but pasty texture)
Toluene
Insoluble
Soluble
Hexanes
Slightly Soluble
Soluble
Resorcinol
Cold (Room Temp.)
Hot (Boiling)
Water
Soluble
----------------
Toluene
Insoluble
Soluble
Hexanes
Insoluble
Slightly Soluble
4-amino 1-napthalenslfonic acid, sodium salt
Cold (Room Temp.)
Hot (Boiling)
Water
Slightly Soluble
Soluble (didn’t dissolve back)
Toluene
Insoluble
Insoluble
Hexanes
Insoluble
Slightly Soluble (ppt. out quick)
