Lab Report 3 Steam Distillation and 4 Crystallization Essay
Reuven Ilyayev Lab Instructor: Maciej Domaradzki Labs 3 & 4 09/19/11 Objective: In steam distillation lab (lab 3), we must obtain pure Eugenol from cloves through the process of steam distillation. In the crystallization lab (lab 4) part 1, we must acquire the best possible pure crystallization of acetylsalicylic acid from aspirin and in part 2 we must obtain a similar pure crystallization of benzil from an impure mixture of benzil. Materials: In lab 3, we used 75 g of cloves from which we must extract Eugenol.
Water was largely used as a solvent.
A polar solvent used was Dichloromethane. The drying agent used was Calcium Chloride. An acid and a base used were hydrochloric acid and Sodium Hydroxide, respectfully. The equipment used were a thermometer & holder, separatory funnel, classen adapter, 3-way adapter (distillation adapter), triple neck round bottom flask, west condenser, vacuum adapter, Erlenmeyer flask, 500ml & 50 ml beaker, Bunsen burner, rubber tubing, clamp holder & extensions, and graduated cylinder.
For both parts of lab 4, the heating source was the hot plate, the substances were heated in a 100ml Erlenmeyer flask, filtered using filter paper and a funnel with a neck, beakers, vacuum flask for additional filtration, and an electronic scale for weighing the crystals.
The solvent used for both parts was 95% Ethanol that was also dripped on the crystals for purification. Ten tablets of aspirin were used in part one. Two grams of impure benzil were used in part two. Procedure: Lab 3 involved an intricate lab with many steps. We began by obtaining 75 grams of cloves and stuffing them into our triple neck round bottom flask.
Then we poured 200 ml of water into the flask, put a stopper into 2 of the 3 necks except the middle one, and inserted a Classen adapter into that center neck. Into the Classen adapter went a separatory funnel in one neck and a 3-way adapter in the other neck. The Separatory funnel was filled with 50 ml of water. A thermometer and its holder were inserted atop the 3-way adapter for vapor temperature measurement. The side of the 3-way adapter was inserted into a west condenser, which itself was inserted into a vacuum adapter. The vacuum adapter was allowed to drip over an Erlenmeyer flask for collection of distillate.
The entire setup was supported by clamp extensions & holders attached at the neck of the triple neck round bottom flask and the vacuum adapter for maximum stability and minimal leakage of vapors. The Triple neck flask was elevated over a Bunsen burner as a heat source. The water in the triple neck flask was brought to a boil, while doing our best to keep it from foaming. The aim here was to distill 60 ml of distillate. As soon as we collected close to 30 ml of distillate we added an additional 50 ml of water into the triple neck flask from the separatory funnel to keep the cloves submerged.
Once the entire 60 ml of distillate was collected we needed to rid it of its water content. We transferred all of the distillate to our empty separatory funnel. We added 15 ml of Dichloromethane to the separatory funnel, inverted it (notice two layers forming), let the pressure out, and drained the organic material that was located at the bottom layer of the funnel into a separate collection beaker. This was done three times. For separate experimentation and reference of weight comparison a 5 ml sample of the not yet pure Eugenol drawn from the collection beaker.
After drying with Calcium Chloride the Dichloromethane was boiled out on a hot plate, the remaining impure Eugenol was weighed, and stored away for later experimentation. The remainder of the impure Eugenol was treated with Sodium hydroxide to deprotonate the Eugenol. This was done three times in the separatory funnel adhering to the same principle of inversion and releasing the build up in pressure. However, from the two layers formed we expel the lower Dichloromethane layer and kept the top aqueous layer each time.
Afterward, the remainder of the deprotonated Eugenol in the aqueous layer was acidified with Hydrochloric acid and tested for pH value with a piece of litmus paper. Adding 15 ml of Dichloromethane three times, inverting, and draining the bottom layer each time then extracted the Eugenol. To evaporate the Dichloromethane we boiled the Eugenol-Dichloromethane mixture on a hot plate in a collection jar. The pure Eugenol was then weighed. In part 1 of lab 4, we obtained ten tablets of aspirin to purify and 10 ml of 95% Ethanol to be our solvent.
The tablets and Ethanol were mixed in an Erlenmeyer flask and heated until a gentle boil. The contents were then swirled to prevent bumping and promote even dissolving. We aimed for a clear liquid with white solid matter floating. As soon as this was achieved the contents of the flask was filtered through a funnel with a neck into a small beaker and allowed to cool to room temperature. While filtering we kept in mind not to allow any of the floating solid into the filtrate. In the process of cooling we watched out for crystallization.
Once the beaker cooled to room temperature, to speed the process of crystallization, the beaker was immersed into an ice bath. After a few minutes, we believed the crystallization was at its maximum. We filtered out the crystals and allowed them to dry atop a vacuum flask on filter paper in a funnel. Air was continuously sucked out to promote drying. To aid the drying process the crystals were washed with drips of ethanol and evenly distributed across the filter paper with a spatula. After a wait time of around 10 minutes, we scraped the dry crystals of the filter paper and weighed them.
All utensils were cleaned and made ready for part 2 of lab 4. In part 2 of lab 4, we had a similar process with some difference in solutes. We obtained 2. 0 grams of impure benzil and mixed it with 10 ml of Ethanol. The exact same process in part 1 was repeated in part 2. However, our aim in part 2 was to see a clear liquid with black powder floating, unlike that of part 1. An additional difference was that we saved our crystals in part 2 for further experimentation at a later time. Class notes: Steam distillation is an ideal method when using two compounds that are immiscible (i. . , water & oil or Benzene & water). Benzene being the organic solvent that is non-polar and water the inorganic solvent that is polar, creates a dilemma since the two can-not be mixed together. When vaporizing something the vapor pressure must equal the applied pressure. This results in liquid turning to gas. If two immiscible compounds have the same vapor pressure then they will have the same boiling point. Another example would be water & naphthalene, in which water depresses naphthalene’s boiling point. When water boils it creates steam.
This steam can be used to pick up particles. One can use steam distillation to pick up immiscible compounds. In our case, the solvent is water and the solutes are the cloves (potentially Eugenol oil). Eugenol oil can be used as an anesthetic. To release the contents of the cloves we can boil them. We can implement the Gaffney principle of “heating the hell out of it”. When a cell is heated at extreme temperatures it will lyse, resulting in the release of its inner contents. Eugenol is an organic molecule consisting of a benzene ring, hydroxyl group, and methyl group for the most part.
In addition, it is a derivative of phenol. The cloves also contain the derivative of Eugenol, which is Acetyl Eugenol. Eugenol has a very sharp boiling point of 255 degrees centigrade. One can purify a solid by the process of crystallization. To begin the process of crystallization, pick a solvent that will not dissolve the chosen solute at room temperature, but only when the solvent & solute mixture is brought to a boil (reflux). Some common examples of solvents used with different boiling points are Ethanol, Acetonitrile, Hexane, and Toluene.
One should try to avoid water as a solvent due to its inorganic & polar properties. A property desired from a solute is not to dissolve at room temperature, but only in a refluxing solvent. If the solute is not dissolving, gradually add more solvent to the refluxing mixture. Once no more solute is visible in the mixture that is a good indicator that it has all dissolved. Sometimes after the solute has dissolved there might be some contents still visible and floating in the solvent. These would normally be known as impurities (ex. Charcoal).
Organic compounds are usually colorless or yellow. To rid the solvent of unnecessary impurities, one should quickly filter the mixture as soon as the solute has disappeared (dissolved). After filtration, one can promote crystallization by allowing the mixture to cool to room temperature. If there are not too many crystals visible at room temperature, one can place the solvent in an ice bath to aid the process. The crystals can be obtained by simply filtering them out of the solvent. Ethanol is great for washing and drying the crystals, since it will not dissolve them at room temperature.
Our solutes in this lab are Aspirin and impure Benzil. An active ingredient in Aspirin is Acetylsalicylic acid and the inactive ingredient is binder. Aspirin will not dissolve in Ethanol at room temperature. However, if one should bring Ethanol to a reflux, aspirin can be dissolved. Once aspirin is dissolved it will leave behind its binder floating. Binder should be filtered out. Each tablet of aspirin contains 325 mg of active ingredient. We shall use 10 tablets, equating in ideal conditions to a 100% yield of 3. 25 grams. When using impure Benzil, Ethanol can be the solvent too.
When Ethanol is brought to a reflux, the Benzil will dissolve and leave behind its impurities. The impurities remaining are charcoal due to the black color of the floating residue. The impurities are easily filtered out with a funnel and filter paper. Observations: In the steam distillation lab, our first observation was the color the water & clove mixture when brought to a reflux. The mixture turned a dark brown color. Then once the distillation process was underway, we witnessed the distillate collected had a white milky substance floating. The milky substance was oil and the rest was water.
We added Dichloromethane to the mixture and noticed the oily layer separated from the water. The organic layer that contained the oil descended to the bottom and the inorganic layer rose to the top. Once we extracted the organic layer, we wanted to dry it with Calcium Chloride. This process yielded white particles resembling little Styrofoam specks floating on the surface of our organic extract. After extracting the chemically dried mixture and boiling out the Dichloromethane, we treated the mixture with Sodium hydroxide. This reaction yielded two layers.
The two layers consisted of Dichloromethane on the bottom and an aqueous oily white layer on the top. We acidified the remaining aqueous oily layer with Hydrochloric acid and tested the pH level with litmus paper that turned pink. Once again the mixture was treated with Dichloromethane, separating the contents into two layers. We extracted the organic layer and boiled out the Dichloromethane yielding a yellow thin film of Eugenol oil. In the crystallization lab, our first observation was the milky liquid that appeared once the aspirin began to dissolve in the refluxing Ethanol.
Once all the aspirin dissolved, white binder residue remained floating. The binder was then filtered out, leaving behind a clear liquid. Crystallization began once the liquid started approaching room temperature. The greatest noticeable proliferation of crystals was when the mixture was placed in an ice bath. When the crystals were filtered out of solution they appeared white in color. As for the impure benzil crystallization, we observed dark impurities (charcoal) floating on the surface of the solution. Once the impurities were filtered out, we noticed a yellow clear liquid remaining.
The crystals extracted by filtration from the yellowish liquid were yellow themselves. Results: 75 grams of cloves yielded . 05 grams of pure Eugenol oil. 10 tablets of Aspirin totaling to 3. 25 grams of Acetylsalicylic acid gave us a yield of . 94 grams. 2. 02 grams of impure Benzil gave us a yield of . 03 grams of pure benzil. Discussion: Through steam distillation, 75 grams of cloves (potential Eugenol oil) gave us a yield of . 05 grams of Eugenol oil. This creates a question in our mind. How come our yield was so minute?
A few factors could come into play that would diminish our yield capacity. Factors such as a lack of control and impure chemicals used. The lack of control in particular would be poorly fastened joints or leaky thermometer holders allowing the escape of vapors, no vacuum-sealed system to protect the experiment from temperature fluctuation, impure glassware that could potentially contaminate the experiment, the poor reflux of the water/clove mixture resulting in the reduced pickup of Eugenol by the vapor particles, and a poorly calibrated weighing apparatus.
Impure chemicals such as reagents and solvents can play a factor in the pure isolation of Eugenol from the cloves too. Impure Calcium Chloride would impede the drying process, Dichloromethane would not separate enough Eugenol out of the water, Sodium Hydroxide would not deprotonate enough Eugenol, and Hydrochloric acid would not acidify enough back for Dichloromethane to separate. In the crystallization experiments, 10 tablets of aspirin gave us . 4 grams that seemed like an extremely minute amount compared to the ideal 3. 25 grams we could have isolated in a perfect experiment. In the crystallization of Benzil, from the 2. 0 grams of impure Benzil we isolated only . 03 grams. We begin to wonder what could have gone wrong. Once again, a lack of control and impure chemicals used seemed to be the perfect suspects in our poor results.
Some aspects of a lack of control would be not enough desired solute dissolving with our solvent, non- dissolved solute being filtered out with our residue of impurities, during filtration crystallization might have occurred causing crystals to be filtered out of the solution, room temperature might have been too low, which caused a rapid temperature drop that trapped impurities, and parts of the crystals might have been lost during the drying process within the vacuum flask. Lastly, the solutes or solvents used might not have been entirely pure resulting in poor isolation of our desired substances.
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