Steam Distillation

CONTENTS CONTENTS| PAGES| 1) Abstract| 2-3| 2) Introduction| 4-6| 3) Objectives, Materials and Apparatus, Chemicals| 7| 4) Method| 8| 5) Results| 9-11| 6) Discussion| 12| 7) Conclusion| 13-14| 8) References| 15| ABSTRACT This experiment is about steam distillation by using Dalton’s Law. The objectives of this experiment are to demonstrate a separation of a mixture by using steam distillation and next to prove that Dalton’ Law and ideal gas law are applicable in steam distillation. Dalton’s Law; While Ideal Gas Law; This experiment is conducted by placing 2mL of Turpentine and 15mL of water into the flask. 0mL graduated cylinder is used as the receiver. All the connections are make sure tighten. Next,two boiling chips are added to ensure smooth bubbling and prevent bumping of the liquid up into the distillation head. The heating mantle is adjusted to give vigorous boiling. The first 1. 5mL of distillate is discarded and the next 5mL is collected. The volumes of th e water and turpentine layers in this distillate are recorded. The recorded volume is then compared with the ideal steam distillation law using the tabulated vapour pressure and densities. The volume of water and turpentine recorded are:Turpentine=1. 7mL Water=3. 3mL turpentine -_-_-_-_-_-_-| -_-_–_-_-_-_Water-_-_-_-_-_-_–_-_-_-_-_-_–_-_-_-_-_-_–_-_-_-_-_-_-| In conclusion,it is proven that turpentine and water can be separated using the steam distillation. INTRODUCTION Dalton's Law of Partial Pressures states that for a mixture of gases in a container, the total pressure is equal to the sum of the pressures of each gas. Where P1 is the partial pressure of gas 1, P2 is the partial pressure of gas 2, and so on†¦ OR In the experiment of the steam distillation,we applied the Dalton’s Law of Partiaal Pressure combined with Ideal Gas Law.Steam distillation is a special type of distillation (a separation process) for temperature sensitive materials like natural aromatic compounds. Steam distillation is employed in the manufacture of essential oil, for instance, perfumes. In this method steam is passed through the plant material containing the desired oils. It is also employed in the synthetic procedures of complex organic compounds. Eucalyptus oil and orange oil are obtained by this method in industrial scale. Figure 1 : Laboratory set-up for steam distillationDistillation Temperature and Composition of Distillate As with ordinary distillations, the boiling point is the temperature at which the total vapor pressure equals the atmospheric pressure. If the vapor pressures of the two components are known at several temperatures, the distillation temperature is found readily by plotting the vapor pressure curves of the individual components and making a third curve showing the sum of the vapor pressures at the various temperature. The steam distillation temperatures will be the point where the sum equals the atmospheric pressure.K nowing the distillation temperature of the mixture and the vapor pressures of the pure components at that temperature, one can calculate the composition of the distillate by means of Dalton’s law of partial pressures. According to Dalton’s law, the total pressure(P) in any mixture of gases is equal to sum of the partial pressures of the individual gaseous components (? A , ? B, etc). The proportion by volume of the two components in the distilling vapor will consequently be equal to the ratio of the partial pressures at that temperature; the molar proportion of the two components (?A and ? B) in steam distillation will be given by the relationship ? A/? B = ? A/ ? B, where ? A + ? B equals the atmospheric pressure. The weight proportion of the components is obtained by introducing the molecular weight (MA and MB) Weight of A / weight of B = (? A x MA) / (? B x MB) Example . Consider a specific case, such as the steam distillation of bromobenzene and water. Since the su m of the individual vapor pressures (see Figure below) attains 760 mm at 95. 2? , the mixture will distill at this temperature. At 95. 2? the vapor pressures are bromobenzene, 120mm and water, 640mm. ccording to Dalton’s law, the vapor at 95. 2? will be composed of molecules of bromobenzene and of water in the proportion 120:640. the proportion by weight of the components can be obtained by introducing their molecular weights. Weight of bromobenze / weight of water = (120 x 157)/(640 x 18) = 1. 63/1. 00 Bromobenzene= {1. 63/(1. 00 + 1. 63)} x 100% = 62% Water = {1. 00/(1. 00 + 1. 63)} x 100% = 38% The weight composition of the distillate will therefore be 62% bromobenzene and 38% water. OBJECTIVE To demonstrate a separation of a mixture by using steam distillation MATERIALS/APPARATUS/EQUIPMENT 00 ml round-bottomed flask, 50 ml Erlenmeyer flask, stoppers, naphthalene, salicylic acid. METHOD Steam Distillation of Turpentine 1. The apparatus for steam distillation are arranged a s shown in Figure 1. 50 ml of distilling flask and 10 ml graduated cylinder is used as the receiver. 2. In the flask, 5 ml, (4. 3g) of turpentine ( bp 156-165 at 760 mm) and 15 ml, of water is placed. 3. Two boiling chips are added and the heating mantle is adjusted to give vigorous boiling. It is essential for the success of this experiment that the mixture boiled rapidly with good mixing of the two phases.Because the point of this experiment is to measure an equilibrium composition and the initial distillate may not have time to equilibrate, the first 1. 5 ml of distillate is discarded and the next 5 ml is collected. 4. The volumes of the water and the turpentine layers at this distillate are recorded. 5. The ratio of the volumes actually found is compared with the ratio calculated from the ideal steam distillation law using the tabulated vapor pressure and densities. 6. The distillation temperature observed is compared with the calculated value. RESULTS turpentine -_-_-_-_-_-_-| _-_–_-_-_-_Water-_-_-_-_-_-_–_-_-_-_-_-_–_-_-_-_-_-_–_-_-_-_-_-_-| Turpentine = 5. 0mL Water = 15. 0mL Weight composition: Water = 15. 0 x 100 20. 0 = 75 % Turpentine = 5. 0 x 100 20. 0 = 25 % The weight composition that will be distillate will be 75 % water and 25 % turpentine. After the mixture have been distilled, here is the result: Total volume of distillate = 5. 0mL Turpentine = 1. 7mL Water = 3. 3mL Weight composition: Water = 3. 3 x 100 5. 0 = 66 % Turpentine = 1. 7 x 100 5. 0 = 34 % Ratio of turpentine to water : Turpentine : Water 0. 34 : 0. 66Weight of turpentine/ Weight of water = [0. 34 x [12(10)+1(16)]] / [0. 66 x [1(2)+1(16)]] = (0. 34 x 136) / (0. 66 x 18) = 46. 24 / 11. 88 = 3. 8923 Turpentine = [ 46. 24 / (46. 24+11. 88) ] x 100% = 79. 5595 % Water = [ 11. 88/ (46. 24+11. 88) ] x 100% = 20. 4405 % Temperature, T/C| Volume of distillate, V/mL| 94| 1st 1. 5mL| 94| 1| 94| 2| 94| 3| 94| 4| 94| 5| DISCUSSION 1. What properties must a substanc e have for a steam distillation to be practical? For steam distillation of a substance to be carried out, the substance must be heat sensitive. It must possess a lower boiling point than water.This method is also advisable for highly volatile liquids because highly volatile liquids denatures at high temperatures. 2. What are the advantages and the disadvantages of steam distillation as a method of purification? Among the advantages of steam distillation is organic compounds which is steam distilled will evaporate at lower temperatures, most probably below their temperature of denaturation. Besides that, heat sensitive aromatic compounds which cannot be distilled by direct heating can be processed. On the other hand, the disadvantages of this method are this method is not exactly suitable for all types of aromatic oils.Only certain types of aromatic oils are suitable to be processed using this method. Furthermore the heat is difficult to control causing the rate of distillation to be variable. -Our group apparatus got some problems. The turpentine that has been distillated accumulated at the joint of the apparatus. This is because the apparatus less slope, leads the turpentine to accumulate, resulting long time to collect the distillated turpentine. CONCLUSION Steam distillation is a special type of distillation (a separation process) for temperature sensitive materials like natural aromatic compounds.Many organic compounds tend to decompose at high sustained temperatures. Separation by normal distillation would then not be an option, so water or steam is introduced into the distillation apparatus. By adding water or steam, the boiling points of the compounds are depressed, allowing them to evaporate at lower temperatures, preferably below the temperatures at which the deterioration of the material becomes appreciable. Therefore, as the conclusion, it is proven that turpentine and water can be separated by using steam distillation.It is also known that water ha s a higher density than turpentine. Next, Dalton's law (also called Dalton's law of partial pressures) states that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture. This empirical law was observed by John Dalton in 1801 and is related to the ideal gas laws. On the other hand, the ideal gas law is stated as the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitationsTherefore, as both of these laws are involved, we can conclude that both Dalton’s Law and Ideal Gas Law are applicable in steam distillation. Based on the result of the experiment, water contains 80% and turpentine contain 20% portion. Some errors might have occurred during the experiment that caused the results to be differed from the theory. During the experiment, the apparatus must handle carefully because it is easily broken. To increase the accuracy of the result, thermometer is used in the flask so we can read the temperature in the flask.We must use stopper to close the flask because it can avoid the water vapour escape to the environment REFERENCES John R. Dean, Alan M. Jones, David Holmes, Rob Reed, Jonathan Weyers and Allan Jones (2002). Practical Skills in Chemistry. Edinburgh Gate, Harlow, Great Britain: Prentice-Hall Carl W. Garland, Joseph W. Nibler, David P. Shoemaker, (2003). Experiments In Physical Chemistry. 7th Edition. New York, N. Y. : McGraw-Hill Umland and Bellama (1999). General Chemistry. 3rd ed. Pacific Grove, CA: Brooks/Cole Publishing Company APPENDICES Steam Distillation Experiment 2: Isolation of Eugenol from Cloves Background; Readings on Vapor pressure, Raoult’s Law from TRO: A mixture of the essential oils, eugenol and acetyleugenol, will be steam distilled from cloves. These compounds are isolated from aqueous distillate by extraction into dichloromethane. The dichloromethane solution is shaken with aqueous sodium hydroxide, which will react with eugenol, to yield the sodium salt of eugenol in the basic aqueous layer, and acetyleugenol in the organic layer. The basic aqueous layer can be acidified to re-extract eugenol from it.And the organic layer can be dried and concentrated to yield acetyleugenol The principle of steam distillation is based on the fact that two immiscible liquids will boil at a lower temperature than the boiling points of either pure component, because the total vapor pressure of the heterogeneous mixture is simply the sum of the vapor pressures of the individual components (i. e. PT = PoA + PoB, where Po is the vapor pressure of the pure liquids). This leads to a higher vapor pressure for the mixture than would be predicted for a solution using Raoult’s Law(applies for iscible mixtures) (that is PT = Po(A)n(A) + Po(B)n(B), where n is the mole fraction of the component in the mixture). The higher total vapor pressure leads to a lower boiling point for the mixture than for either single component. The boiling point of eugenol, an oil found in cloves, is 248  °C, but it can be isolated at a lower temperature by performing a co-distillation with water. Steam distillation allows separating substances at lower temperatures which is useful since many organic compounds tend to decompose at high temperatures which regular distillation would require.For steam distillation to be successful, the material to be isolated must be insoluble in water. Usually   these compounds have a low vapour pressure. After mixing them with water, however, the mixture will distil when the sum of the two vapour pre ssures reaches atmospheric pressure. It follows, then, that this must happen below the boiling point of water. Note that by steam distillation, as long as water is present, the high-boiling component vaporizes at a temperature well below its normal boiling point without using a vacuum.Since eugenol is not soluble in water, the concentration of the eugenol in the vapor over the boiling eugenol– water suspension does not depend on concentration of the eugenol. The relative amounts of eugenol and water in the vapor simply depend on the vapor pressures of the pure materials. The vapor pressure of water at 100  °C is 760 torr, and the vapor pressure of eugenol at 100  °C is approximately 4 torr; (Note, the suspension boils when it’s vapor pressure is equal to the external pressure.Since both the eugenol and the water are contributing to the vapor pressure of the suspension, the suspension will boil before either pure substance would normally boil. ) Since the distillate will contain both water and eugenol, the eugenol must be extracted from the water using an organic solvent. Once the eugenol is extracted into an organic solvent,the organic layer is separated from the aqueous layer and dried. The eugenol is finally isolated by evaporation of the organic solvent. When   the sum of the separate vapor pressures equals the total pressure, he mixture boils and P =P(A) + P(B) Where PA is vapor pressure of pure water A PB is vapor pressure of pure B 1 Then the vapor composition is Y (A)= PA/P Y(B) =PB/P Dalton’s Law: PAV1 = nART1 and PBV2 = nBRT2 V1 = V2 and T1 = T2 n = moles, The ratio moles of B distilled to moles of A distilled is OH OCH3 OAc OCH3 Eugenol AcetyleugenolObjectives: To extract Eugenol and Acetyleugeonol from cloves To separate the mixture of eugenol and acetyleugenol using their acid- ­? base properties. To characterize eugenol and acetyleugenol using TLC(Rf values) andRefractive index. Glassware: Beaker to mass the cloves, Er lenmeyer flasks(2, 50- ­? ml), storage container+ distillation glassware(there should be an assembly in the fume hood) Procedure: Week 1: Steam Distillation Place 10 g of whole cloves (ground using a mortar and pestle by the teacher) in a 100-mL round-bottom flask, add 50 mL of water, and set up an apparatus for simple distillation- steam (will be set up in the fumehood and you can draw the set up while in the lab) will be generated in situ(50 ml of water added to the flask will generate the steam).Heat the flask until boiling begins, then reduce the heat just enough to prevent foam from being carried over into the receiver. Use a 50-mL Erlenmeyer flask as a receiver(the distillate will collect in the flask thro a funnel) and transfer periodically your distillate to a 50-mL graduated cylinder. While you have removed one receiver, do not forget to replace the Erlenmeyer flask with a second one(that is clean and dry). 2 Caution: It is important that the cloves remain covered with wa ter at all times. Or else, the cloves will burn and smoke!Also, the distillation has to be steady. If not the mixture will foam and the foam will drop down the condenser into the receiving flask. And this would contaminate the distillate. Save the distillate in a tightly capped bottle for the following week. Week 2: Separation of Eugenol and Acetyleugenol via acid/base extraction Place the 50 mL of distillate in a 125-mL separatory funnel and extract with three 10-mL portions of dichloromethane. Combine the dichloromethane extracts and reserve 1 mL for thin layer chromatography. teacher will explain this step) To separate eugenol from acetyleugenol: pour back the dichloromethane extracts into the separatory funnel, extract the dichloromethane solution with 5% aqueous sodium hydroxide solution. Carry out this extraction three times, using 5-mL portions of sodium hydroxide each time. KEEP the aqueous extracts (it contains eugenol) and dry the organic layer over sodium sulfate (add eno ugh so the drying agent no longer clumps together but appears to be a dry powder as it settles in the solution).Swirl the flask to complete the drying process and let the drying agent settle for 1 minute before decanting into a DRY and TARED Erlenmeyer flask, rinse the drying agent with two 2-mL portions of dichloromethane. Evaporate the solution on a steam bath, the residue should be aetyleugenol. Acidify the combined aqueous extracts to pH 1 with concentrated hydrochloric acid (use Litmus paper to monitor the pH), and then extract the eugenol with three 5-mL portions of dichloromethane.Dry the combined extracts over sodium sulfate, as done before, decant into a DRY and TARED Erlenmeyer flask, and evaporate the solution on a steam bath, the residue should be eugenol. Cleaning Up: Combine all aqueous layers, neutralize with sodium carbonate, dilute with water, and flush down the drain. Any solutions containing dichloromethane should be placed in the halogenated organic waste contain er. Wash up all glassware with soap and water. Analysis: Calculate the weight percent yields of eugenol and acetyleugenol oils based on the weight of cloves used. Analyze your products sing refraction index. Analyze your products using thin layer chromatography (TLC). Eluent: dicloromethane-hexane (1:2 or 2:1)Vizualization: under UV light and iodine chamber AS Co AE AS – Acetyleugenol Standard Co – Co-spot AE – Acetyleugenol Extract ES Co EE ES – Eugenol Standard Co – Co-spot EE – Eugenol Extract ES Co CM ES – Eugenol Standard Co – Co-spot CM – Crude Mixture First a TLC plate is prepared by spotting the purified unknown and an authentic sample of each possible compound. Then the TLC plate is developed. For the next step (co-spotting), an authentic sample of the 3 ompound closest in Rf value to the unknown is chosen. TLC co-spotting of a second plate allows for preliminary identification of your compound. Three spots are applied to the adsorbent on the baseline of the TLC plate: the purified unknown, an authentic sample, and a co-spot of unknown and authentic sample. If the developed TLC plate shows only one row of spots, it can be concluded that the unknown has been purifed, and that the unknown is possibly the same compound as the authentic sample.However, because Rf values are relative, not absolute, some compounds may have very similar Rf values Pre- ­? ab: FOR WEEK 1 only: All the required formulae for the caculations have been presented here. Hence googling is not required. MSDS is required for the following chemicals: Eugenol and acetyl eugenol. Pre- ­? lab should be complete to the best of your ability before the lab. Answers will be discussed during the lab. For the procedure : You will draw the glassware set up when you come to the lab; Just come prepared with titles, objectives, MSDS. Questions from pre-lab should ensure that you have understood the theory behind WEEK 1 ; Distillation . 1a. What is the vapour pressure of benzene at 80 egrees celcius. Explain the term vapour pressure. 1b. What is an azeotrope? How would the term azeotrope apply in this experiment? 2a. The vapor pressure of water at 99oC is 733 torr. What is the vapor pressure of eugenol that codistills at this temperature? The amount of the substance X that co- ­? distills together with the water is given by Pwater/px = nwater/nx n(water) = moles of water n(X)= moles of Eugenol 2b. Calculate the mass of eugenol that co-distills with each gram of water at 99oC. How many grams of water must be distilled to steam distill 2 grams of eugenol from an aqueous solution?Calculate mass% for both eugenol and water. 3. What is the difference between essential oil and fatty oil? What would be suitable IUPAC name for eugenol and acetyl eugenol? 4. Based on the formulae presented so far, cite one disadvantage of steam distillation of organic compounds. 5. Steam distillation may be used to separate a mixture of 4- ­? nitrophenol and 2- ­? nitrophenol. The 2- ­? nitrophenol distills at 93 degrees but the 4- ­? nitrophenol does not. Explain. 6. List your observations during the lab: Record the temperatures at various times, nature of the distillate, odour†¦.. 4