Record exact mass of the flask, cover, copper wire and condensed liquid. The flask should contain some of the original liquid. Keep the flask secured in the clamp until it has cooled to room temperature. Cooling may also be done faster by submerging the flask in an ice bath. While waiting for the flask to cool to room temperature, obtain the barometric pressure reading of the room and record it.ġ2. When the flask has cooled, wipe off traces of water on the outside of the flask and weigh the flask. ![]() ![]() The clamp may be hot use thermal gloves or paper towels to protect from heat, if necessary. The pictures below show the close up of what the evaporating materials look like.ġ1. Carefully remove the flask from the water bath by raising the clamp on the ring stand. The dithizone dye is intensely green in solution, but dries to a dark solid residue.ġ0. When you are sure that the liquid has completely vaporized, record the temperature of the water bath. Turn off the Bunsen burner. Continue heating and watch the green color of the dithizone disappear – this indicates that the liquid sample has completely vaporized. If the water starts to boil while the liquid is evaporating, record this observation. Use enough water to submerge a 125-ml Erlenmeyer flask but not enough to overflow the beaker. Check with your instructor as to the specific procedure to use. The wire screen is necessary to disperse the heat from the flame to avoid breaking the beaker due to thermal shock.Īlternatively, a different setup may be used with hot plates instead of Bunsen burners. Add additional water as needed to maintain the level of water. Maintain the temperature of the water at around 95☌, or just below boiling throughout this experiment. Monitor the temperature of the water bath with a thermometer. Occasionally stir the water in the water bath with a stirring rod. Other thermometers may be used as needed or available.Ĩ. The thermometer is held in place with a buret clamp or a thermometer clamp. One way to set up the apparatus is shown in the picture on the left. Carefully attach a clamp to the neck of the flask and lower the flask, slightly tilted, as deep into the hot water bath as possible. The beaker can be secured with an oversize ring to prevent it from falling over.ħ. Adjust the height of the ring to make sure that the hottest part of the flame of the Bunsen burner touches the bottom of the beaker. Prepare a water bath by filling a 600-mL beaker with about 400 mL of tap water. Add a few boiling chips. Place it on a wire gauze on an iron ring attached to a ring stand. It is important to not lose any of the foil or copper wire.Ĥ. Replace foil cover and crimp it tightly around the opening of the flask. Secure the foil with the copper wire. Make sure that there is no loose foil hanging down that may collect moisture from the water bath during the experiment.ĥ. Use a pin to poke 1 small pinhole on the foil cover of the flask to allow the air and excess vapor to escape and maintain a pressure inside the flask that is equal to the atmospheric pressure.Ħ. ![]() Mass of Erlenmeyer flask with cover, dithizone and copper wireģ. Carefully remove the copper wire and aluminum foil cover and transfer about 5 mL of the liquid sample into the flask. Record mass to at least the nearest 1 milligram (0.001 grams). ![]() Weigh the flask, cover, dithizone crystal, and copper wire. The crystal of dithizone is in the photo. It should look something like the following: Record the name of the liquid sample here, or the identification number of the unknown:Ģ. Obtain a clean, dry 125-mL Erlenmeyer flask, add one small crystal of dithizone (a dye) about the size of a grain of salt, and loosely cover it with a square piece of aluminum foil (about 5 cm x 5 cm). Secure the aluminum foil by tying a copper wire. Your instructor may choose to issue the liquid as an unknown sample. Obtain a liquid sample from your instructor. Additional liquids may also be added at the request of the instructor.ġ. Liquid sample in this experiment may be any of the following: acetone, isopropyl alcohol, ethyl acetate, or cyclopentane. Use tongs or mitts to handle hot flasks and beakers.ĭiscard any excess unknown liquids in the organic waste container in the fume hood. Use of eye protection is recommended for all experimental procedures. Section 2: Safety Precautions and Waste Disposal \( \newcommand=\) , and T is the Kelvin temperature.
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