EXPERIMENT 3 STEAM DISTILLATION I. OBJECTIVES 1. 2.
To assemb assemble le and use use a simpl simple e dis distil tillat lation ion setup setup in the separa separatio tion n of volatile substances from non-volatile materials. To isolate essential oils from plant sample.
II. PROCEDURE A. Ste Steam am Disti Distilla llatio tion n
NOTE: Organic solvents are generally flammable and their vapors are toxic. Avoid open flames and do not inhale vapors. Weigh out about 200 grams of fresh finely cut citronella grass, citrus rind or other suitable plant material. 2. Mix the sample with distilled water in the sample flask. Add enough water such that the flask is about 2/3 full. 3. Assemble the rest of the set-up. 4. Check all connections for tightness. Show your set-up to your instructor for inspection. 5. Heat the sample flask. 6. Collect about 200 mL of distillate into a 250-mL separatory funnel. 7. Record all observations. B. Separation of the Essential Oil from the Steam Distillate 1.
1. If a dist distin inct ct oil oil laye layerr sepa separa rate tes s from from the aque aqueou ous s laye layerr of the stea steam m distillate, drain the aqueous layer slowly out of the separatory funnel. If the oil layer is not distinct or if some oil droplets are dispersed in the distillate, salting out may be necessary.
2. Place a spatula of the sodium chloride into the separatory funnel and gently shake or swirl the contents. Let it stand to allow the oil layer to separate then proceed with the drawing out of the aqueous layer. 3. Transfer the remaining oily layer into a previously weighed clean vial using a dry glass dropper. 4. Determine the weight and percent yield of the oil. 5. Record all observations. 6. Label the vial properly, indicating the source, laboratory section, group number and date. 7. Submit to your Lab Instructor. III. DATA AND OBSERVATIONS Weight of the sample (g) Weight of empty vial (g) Weight of empty vial + oil (g) IV. QUESTIONS What characteristics must a substance possess for it to be separated from a heterogeneous mixture by steam distillation? 2. What is the advantage of employing steam distillation in extracting oil? Why can’t we just press the oil out of the sample or extract it directly with an organic solvent? 3. A mixture of immiscible liquids (both water-insoluble) is subjected to steam distillation. At 90°C, the vapor pressure of pure water is 526 mm Hg. If the vapor pressure of Compound A is 127 mm Hg and that of B is 246 mm Hg at 90°C, a. What is the total vapor pressure of the mixture at 90°? b. Would this mixture boil at a temperature above or below 90°? c. What would be the effect on the vapor pressure and boiling temperature by doubling the amount of water used? 4. Research on the essential oil you have isolated from your source. Draw its structure. Based on literature, what is its boiling point/vapor pressure? What are the uses of this oil? 1.
