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T07-C200

David Blicq A425M dblicq@rrc.mb.ca  (update 01/04/2010)  DIRECTORY I BIO I NOTICE BOARD

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Table of Contents

Laboratory Safety

Laboratory Records

Lab 1 - Use of Solubility to Characterize Organic Compounds

Lab 2 - Melting Point Determination

Lab 3 - Purification Method: Crystallization

Lab 4 - Purification Method: Distillation

Lab 5 - Volumetric Analysis of Analgesic Tablets

Lab 6 - Formal Research Project

Lab 7 - Chemical Measurement of Water Quality

Lab 8 - Isolation of Caffeine from Tea Leaves

ATTENTION!

These laboratory exercises have been created for the students of the Chemical and Biosciences Technology program at Red River College, Winnipeg Manitoba. By design, the exercises contain selected errors and problems intended for the student to troubleshoot and remedy in the course of the activities.

Laboratory Safety

In chemical experimentation there are always hazards present due to materials, equipment, and the reaction of materials. There is a simple rule of thumb:

WHAT YOU DON’T KNOW CAN HURT YOU!

By following basic safety precautions you can minimize the probability and consequences of an accident.

                   PROTECT YOUR EYES!

                    1. Wear safety goggles when there is a risk of splattering, when working with

      corrosive chemicals, and when working with apparatus under reduced or increased pressure

      2. Never have your eyes over a vessel opening! Look at a vessel but never into it.

      DO NOT POISON YOURSELF!

      1. Regard all chemicals as poisons.

      2. Do not eat in the laboratory.

      3. Wear gloves when using chemicals that pose a health hazard by rapid adsorption through intact skin.

      4. Handle obnoxious chemicals in a fume hood.

      5. Deal with all spills immediately.

      6. When finished working, wash hands thoroughly.

      GUARD AGAINST FIRE!

      1. Regard all organic liquids as flammable.

      2. Solvents are to be stored only in closed containers: never in an open beaker.

      Familiarize yourself with the location of Fire extinguishers, eye-washes, safety showers and first aid equipment in your laboratory!

      NOTIFY YOUR INSTRUCTOR IMMEDIATELY OF ANY / ALL ACCIDENTS!

      LABORATORY PREPARATION

      Students are expected to prepare for laboratories by completing the following:

      1. Experiments are to have been read and an outline written up prior to each lab session.

      2. Potential hazards and handling considerations for each experiment are to written up in your "Lab Log" before the laboratory session.

      LABORATORY RECORDS

  1. Your laboratory records, and your ability to record and present key technical data in a meaningful way are crucial skills in the BioSciences industry. With many industries / institutions being regulated (FDA / European union, etc.) complete accountability is essential.
  2. Most facilities are routinely audited, which involves highly detailed reviews of all records. Both you and the auditor(s) must be able to clearly account for each and every aspect of your work.
  3. Work prepared as part of these laboratories will require this same level of accountability, and you will be graded on both the accuracy and level of "information recovery" from your lab-log.

       IN-LAB WORK (Lab Log)    

      All work is to be recorded in a hardbound book, with numbered pages. This is to ensure that data is never misplaced or "illegally substituted" after the fact. The rule of thumb is: write it down and leave it.

    1. Each experiment must be clearly titled and described, including calculations, methods and results. This high level of organization is protection against later reviews, audits, etc. With each experiment clearly written up in an organized fashion data retrieval is easy.
    2. All chemicals are to be identified by manufacturer and lot #. Again complete accountability is required: you must be able to account for the "history" of each component you have used (i.e. whether a component was past its’ expiry date). This is a standard review item during audits.
    3. Dates of calibration of appropriate equipment should be included. If you have used specialized hardware that can be calibrated, (i.e. calibration is required to ensure proper functioning) the hardware must have a sticker indicating "last and next due" calibration. (This may not be possible for some of our laboratory equipment).
    4. Each page must be signed (bottom corner). This is to ensure you and no-one else prepared this work and that you stand behind your work 100%. It also implies that you are responsible and accountable for the work on that page.
    5. Each page must be dated (top corner). To promote record retrieval.
    6. Mistakes are crossed out with a single line and initialed beside the error. You may make hundreds of "writing errors / mistakes" but if each one is signed off correctly that is perfectly acceptable.

YOU WILL BE GRADED BOTH ON CONTENT AND THE ABOVE FORMAT!

Laboratory 1

Use of Solubility to Characterize Organic Compounds

Introduction:

Information can often be obtained about an unknown substance by studying its solubility in water, 5% NaOH, 5% Sodium bicarbonate, 5% hydrochloric acid, and cold concentrated sulfuric acid. For example:

  1. Hydrocarbons are insoluble in water; therefore the fact that an unknown like "ethyl ether" shows partial solubility in water indicates a polar functional group.
  2. Benzoic acid is insoluble in the polar solvent, water, but is converted by dilute NaOH to a salt (sodium benzoate) which is readily water-soluble. This is a strong indication of an acidic functional group.
  3. Deductions can also be made about molecular weight. For example, in homologous series of monofunctional compounds, the members with fewer than (5) carbon-atoms are water-soluble, while the larger homologs are not.

Objective:

The objective of this laboratory is to use a solubility flow-chart to characterize an unknown compound by examining solubility in a number of solvent systems.

Method:

  1. Obtain your unknown sample from the instructor and then follow the flow chart (on the next page) for the general characterization of your compound.
  2. Water solubility: place 0.2 ml (0.1 g of a solid) in small test tube and add (in portions) 3 ml of water. Shake vigorously and after the addition of solvent. If compound dissolves completely, record it as soluble.
  3. Ether solubility: place 0.2 ml (0.1 g of a solid) in small test tube and add (in portions) 3 ml of ether. Shake vigorously and after the addition of solvent. If compound dissolves completely, record it as soluble.
  4. Aqueous acid / Base: place 0.2 ml (0.1 g of a solid) in small test tube and add (in portions) 3 ml of NaOH / sodium bicarbonate / hydrochloric acid. Shake vigorously and after the addition of solvent. Separate (filtering if necessary) the aqueous solution from any undissolved unknown and neutralize with acid or base. Even a cloudy appearance of filtrate is considered a positive test.
  5. Solubility in Concentrated Acids: place 3 ml of acid / solvent in test tube and add 0.2 ml (0.1 g of a solid). Examine for changes in colour / heat etc.

Solubility Flow Chart:

    Obtain a copy of the flow chartfrom the instructor.

Solubility Classes of Organic Compounds (from flow chart)

S2 - salts of organic acids (RCO2Na, RSO3Na), amine hydrochlorides (RNH3Cl), amino acids, and poly-functional compounds (functional groups are hydrophillic) i.e. carbohydrates, polyhydroxyl compounds, polybasic acids, etc.

SA - monofunctional carboxylic acids with (5) or fewer carbons, arenesulfonic acids.

SB - monofunctional amines with (6) carbons or fewer.

S1 - monofunctional alcohols, aldehydes, ketones, esters, nitriles, amides with (5) carbons or fewer.

A1 - strong organic acids: carboxylic acids with more than (6) carbons, phenols with electron-withdrawing groups in the o-, and p- positions, b -diketones.

A2 - weak organic acids: phenols, enols, oximes, imides, sulfonamides, thiophenols, all with more than (5) carbons, b -diketones, nitro compounds with a -hydrogens, sulfonamides.

B - aliphatic amines with (8) or more carbons, anilines (only one phenol group attached to nitrogen) some oxy ethers.

MN - miscellaneous neutral compounds containing nitrogen or sulfur and having more than (5) carbon atoms.

N1 - alcohols, aldehydes, methyl ketones, cyclic ketones and esters with one functional group and 5-9 carbons; ethers with < 8 carbon atoms, epoxides.

N2 - alkenes, alkynes, ethers some aromatic compounds (especially those with activating groups), ketones (other than those in class N1).

I - saturated hydrocarbons, haloalkanes, aryl halides, diaryl ethers, deactivated aromatic compounds.

(Note: carboxylic acid halides and anhydrides have not been classified due to their reactivity.)

Results:

  1. Describe the class of organic compound indicated by your results. Prepare a table characterizing the results for each group.
  2. Draw the listed flow chart in your laboratory log for future reference.

 

Laboratory 2

Melting Point Determination

Introduction

Melting point determination is another simple initial methods which can be used for identifying an unknown sample.

Determination of the melting point of a material is simple: the solid material is slowly heated until a softening or a droplet of liquid is observed. Typically the "melting point" (m.p.) is actually described as a range (melting range) which includes the temperature at which the "first drop" appears (lower limit) and temperature at which the material becomes entirely liquid (upper limit). For sample of most pure organic compounds, this range does not exceed 2° C.

There are three general rules for organic molecules:

bullet Melting points increase with increasing MW (molecular weight)
bullet Symmetrical molecules have higher m.p. than asymmetrical molecules
bullet Branched chain molecules have lower m.p. than linear molecules

In a mixture of organic molecules, the m.p. of each component is normally depressed. This occurs because the impurities (the other components of the mixture) interfere with normal attractive interactions that occur in the pure compound. Also, the mixtures will display a wider melting range.

Objective:

The objective is simple: you will measure the m.p. of three organic compounds and then use the m.p. information to identify an unknown sample. Your m.p. determinations will be conducted two ways: both manually and using an automated melting point analyzer (Mettler FP5).

Method:

  1. Prior to the laboratory,
    you are to reference the molecular formula, melting point and potential hazards of the three known samples: Benzoic acid, Salicylic acid and Urea.
  2. Obtain samples of the three compounds and carefully crush each one on filter paper or paper towel.
  3. For each of the three samples, scrape the powder into a mound with a spatula and pack some of the crushed compound into a capillary tube. The packed material should occupy ~0.5-1.0 cm of the tube and can be tamped down to ensure tight packing.
  4. Manual analysis: place paraffin oil up to the side-arm of the Thieile tubes (Note: do not attempt to wash tubes)
bullet Heat the tubes slowly (1° C / minute is ideal) and look for the initial m.p. (the first softening that appears) and the temperature of complete liquidity (the melting range). Record your data for all three samples.

      5. Automated Analysis: place your three filled capillary tubes within the furnace of the Mettler FP5 apparatus.

bullet Set the temperature "ramp" speed for 3° C / minute
bullet Set the starting furnace temperature for 10° C below the lowest m.p. of your samples.

      6. You will be given an unknown compound from the tested group. Repeat both the manual and automated  procedures to identify the unknown compound.

Results:

  1. Prepare a Table comparing reference m.p. data, your manual measurements and your automated measurements for all tested samples.
  2. Identify the unknown sample.
  3. Draw the chemical structures of your three samples.

Questions:

  1. What are the advantages / disadvantages of both techniques?
  2. What is the significance of the "ramp speed" in the autoanalyzer?
  3. What is a "mixed melting point procedure" and how could it be employed in identifying an unknown compound?

Laboratory 3

Purification Method: Crystallization

Introduction:

Crystallization is a simple method for purifying an organic compound that is solid at room temperature. The method is quite simple: the compound is dissolved in hot solvent (until the solvent is saturated) and then the solution is allowed to cool slowly to a temperature below the melting point of the compound.

If cooling is slow enough, small quantities of the compound solidify and act as "seeds" for crystallization of the remaining product. If the cooling is too rapid the compound will simply precipitate rather than form crystals.

The choice of solvent is critical. Ideally the compound will be soluble in hot solvent and insoluble in cold solvent. Sometimes this is accomplished by mixing two miscible solvents.

Some Commonly used Solvents

Name

Formula

Boiling Point

Water Miscible

Comment

Water

H2O

100

Y

  

Methanol

CH3OH

65

Y

Flammable

Ethanol

CH3CH2OH

78

Y

Flammable

Acetone

(CH3)2C=O

56

Y

Toxic

Ethyl Acetate

CH3CO2CH2CH3

77

N

Flammable

Chloroform

CHCl3

61

N

Toxic

Methylene Chloride

CH2Cl2

41

N

  

Diethyl Ether

(CH3CH2)2O

35

N

Flammable

Cyclohexane

C6H12

81

N

Flammable

Petroleum Ether

CnH2n+2

20-60

N

Flammable

For example, petroleum ether is a mixture of pentane and hexane. Generally, in industrial applications the solution of material to be crystallized is called the "mother liquor".

Objective:

The objective is simple: you will be given an impure sample of benzoic acid, and you will use crystallization to purify your sample.

Method:

  1. Weigh 5.0 g of benzoic acid into a 250 ml erlenmeyer flask.
  2. Place 2-3 boiling chips in the flask.
  3. Add 150 ml of boiling water to the benzoic acid.
  4. Place mixture on a hot plate and heat until the benzoic acid is fully dissolved.
  5. Filter the hot solution through fluted filter paper to remove insoluble contaminants. Collect the filtrate in a pre-warmed 250 ml erlenmeyer flask.
  6. Wash the original flask with 10 ml of boiling water and pass this wash through the fluted filter paper. Add this filtered wash to the mother liquor.
  7. Add 2-3 new boiling chips to the mother liquor and bring the solution to a boil.
  8. Remove solution from heat and cover with an inverted beaker. Allow the mother liquor to cool. While the solution is cooling, set up a filter flask with a Buchner funnel.
  9. Once cooling is complete and crystals have formed, filter the liquor and wash the "filter cake" with cold water.
  10. Place the filter paper on a wash glass, (loosely covered) and place the filter in your lab locker. At the start of next lab weigh your sample to determine yield.

Results:

  1. Create a flow-chart describing your procedure.
  2. Determine your per cent yield.
  3. Draw the structure of benzoic acid.

Questions:

  1. What are the limitations of crystallization as a purification tool?
  2. Why was water used as a solvent in this experiment?
  3. What are "critical nucleii"?

Laboratory 4

Purification Method: Distillation

Introduction:

Distillation is a basic method for purifying a liquid. The process is simple: slowly the liquid is converted to gas (vapourized) then the gas is converted back to liquid (condensation). Distillation takes advantage of differences in boiling points to separate and purify various compounds.

In liquids, molecules can move freely relative to each other although there are attractive forces between the molecules. Some molecules achieve sufficient kinetic energy to overcome the attractive forces and enter the "vapour phase". "Vapour pressure" (mm of Hg) measures the number of molecules capable of entering the vapour phase at a specific temperature and pressure. When atmospheric pressure and vapour pressure are equivalent bubbles of vapour form in the liquid: the liquid is "boiling".

If there is a mixture of two liquids with different boiling temperatures, there will be more vapour from the from the component with the lower boiling temperature. When the temperature of the mixture is raised to the boiling point of the "lower boiling" component, the vapour above the mixture will contain mostly the lower boiling liquid. If this vapour is cooled and collected, it is found to contain a much greater amount of the lower boiling component than the original mixture.

Objective:

The objective of this laboratory will be to use distillation to purify a contaminated ethanol solution.

Method:

  1. Distillation Apparatus: Examine the distillation apparatus set up in the laboratory. The system consists of a distillation flask placed in a heating mantle. A thermometer is placed through a cork in the top of the distillation flask. The sidearm of the distillation flask is connected to a condenser. Cool water is run into the condenser at the inlet closest to the distillation flask and leaves by the higher outlet port. The water cools the evaporated gases flowing through the collector tube that runs through the condenser, which condense back to a liquid state. The liquid flows down the collecting tube to a graduated beaker or collecting vessel.
  2. The sample to be purified by distillation is a mixture of ethanol and contaminating stain. 95% Ethanol has a boiling point of 78.2° C. Obtain 250 ml of sample solution and place the sample and 2-3 boiling chips into the distillation flask.
  3. Set up the distillation apparatus as demonstrated, ensuring that each piece is properly supported by clamps to avoid strain at the glass joints. Do not over-tighten clamps on glassware as there may be heat-expansion during the distillation.
  4. Establish a steady flow of cool water through the condenser, sufficient to keep the condenser cool.
  5. Collect 100 ml of distilled 95% ethanol. Determine the distillation rate (ml / minute).

Results:

  1. Prepare a labeled schematic diagram of the distillation apparatus.
  2. Describe the technical limits to a distillation purification procedure.

Questions:

  1. How could you reduce the boiling temperature of your distillation?

Laboratory 5

Volumetric Analysis of Analgesic Tablets

Introduction:

Analgesic tablets are the most widely used non-prescription drugs in the world. There are many varieties in the marketplace, but the active ingredient is usually the same: acetylsalicylic acid. These tablets are often incorrectly called "Aspirins" after a popular commercial brand, but should be referred to as A.S.A. tablets.

A typical commercial A.S.A tablet will contain not only the A.S.A., but also calcium carbonate and calcium sulfate or starch. The analysis is therefore quite simple: since acetylsalicylic acid is the only acidic component analysis for total acids should indicate the quantity of active ingredient.

Quality control in the pharmaceutical industry is of critical importance since the final products are usually for human consumption.

Objective:

The objective of this laboratory is quantify the amount of A.S.A. present in three different tablets, followed by the quantification of A.S.A. in an unknown tablet.

Method:

  1. Obtain each of the three A.S.A. tablets and weigh them individually to three decimal places.
  2. Powder each tablet (into small pieces) in an Erlenmeyer flask using a stirring rod.
  3. To each labeled flask add 25 ml of 2-propanol and mix for three minutes.
  4. Add (2) drops of phenolphthalein indicator and titrate each sample individually with 0.2M NaOH solution. (The low solubility non-acidic components may re-dissolve during the titration.) During the titration, place a sheet of white paper beneath the flask and stop the titration when a faint pink colour and appears for > 30 seconds. (The molar equivalent of base consumed is equivalent to the molar concentration of acid present.)
  5. Obtain the unknown tablet from the instructor and quantify the A.S.A., content using the above procedure.

Results:

  1. Prepare a Table indicating the A.S.A. equivalent concentration per tablet and compare this to the "listed" values.
  2. Draw the structure of acetylsalicylic acid.

Questions:

  1. What are the limits to this type of simple quantification?
  2. A.S.A. passes through the stomach unchanged but is readily hydrolyzed by the intestinal tract. Explain this behavior.
  3. Describe a process to separate the binder agent(s) from the acetylsalicylic acid.

Laboratory 6

Formal Research Project

Introduction:

As a Research Scientist with a major chemical manufacturer you are often called upon to retrieve and present complicated technical information to help Production and / or Research Managers. In this exercise your manager has requested that you present a formal technical report on an urgent topic area.

There are two very simple requirements for this type of project:

    1. Your response must be quick.
    2. Your report must be meaningful, accurate and concise.

Method:

  1. Select a topic from the instructor’s list.
  2. Using the Internet, you will quickly conduct a search(s) to collect material on the selected topic, possibly using scientific, commercial, or educational web-sites. You will require a minimum of (3) referenced web-sites.
  3. You will prepare a concise formal report (on computer) on the topic, of 2-3 pages in length. The technical information must be presented from your own viewpoint, and not simply copied from the Internet sources, although you may wish to reinforce your presentation with a downloaded photo etc. Your report will present the information in a relevant way, with only "useful" information being included. Useful equipment might include a description of the available equipment, pricing, applications, etc. Your report might follow a similar format:

    Project # -Title

    Date - Name

    Introduction: a brief description of information sought / topic

    Contents: a brief list summarizing the presented material

    Main Topic: the actual data / information recovered

    Recommendations: recommend a course of action, as appropriate

    References: all web-sites used must be clearly referenced

            The formal report is due two weeks after the receiving the assignment.

Laboratory 7

Chemical Measurement of Water Quality

Introduction

One of the most common chemical treatments conducted on a daily basis is the treatment of water. Pre-use treatment typically involves a precipitation or flocculation to remove suspended solid materials (treatment with alum), a treatment to reduce pipe corrosion (treatment with phosphates) and chemical treatment to kill potential pathogenic microorganisms (chlorine). Some municipalities (such as Winnipeg) also use fluorine to promote dental hygiene.

Following municipal or industrial use, wastewater is normally treated before it is returned to the natural watershed. Wastewater treatment usually involves several steps: a primary (mechanical treatment) to remove contaminants, a secondary (chemical treatment) using microorganisms (etc.) in lagoons, reactors or biofilms, and a tertiary treatment (chemical additions to adsorb (i.e. carbon) or to oxidize (i.e. chlorine) contaminants.

Objective:

There are several standard methods for evaluating wastewater after such treatments have been conducted, and this laboratory will test four samples of water using these methods. The tests will include measurement of:

Chlorine: both pre- and post-use water treatment use chlorination. If there are more contaminants than chlorine, all chlorine is consumed. If there is sufficient chlorine (more than the contaminants) there will be residual chlorine present.

pH: is a measurement of the negative log of the hydrogen ion concentration.

Alkalinity: the capacity of the water to neutralize acid

Hardness: the level of dissolved cations (+ve charged ions) in the water.

Method:

  1. Measure and record pH for each sample. If you have not previously done this, you will be instructed on the use of the pH meter and Hach pH kit. Record the pH values from both methods.
  2. Measure residual chlorine in the samples using a comparator:
bullet Fill the viewing tube with test sample
bullet Add the contents of one DPT free chlorine reagent "pillow" to one tube.
bullet Place the blank sample in the left side of the comparator, and place the sample + indicator in the right side of the comparator.
bullet Hold up to a bright, steady light source and rotate the disk until the colours match.
bullet Read and record the mg/ml of free chlorine.
  1. Measure and record
    total chlorine in the sample, using a comparator. (Repeat step #2 but use DPT chlorine reagent pillow.
  2. Measure the Alkalinity by titration (P-alkalinity: phenolphthalein alkalinity)
bullet Add (5) drops of phenolphthalein indicator to 50 ml of test sample in a beaker.
bullet Fill a burette to the zero mark with 0.02N sulfuric acid.
bullet Slowly add acid to the stirring sample until a pink colour develops.
bullet Calculate P-alkalinity as:

         mg/ml CaCO3 = l H2SO4 x 1000 / ml of sample

bullet Add (4) drops of methyl purple to the sample and continue titration until a faint purple colour is seen.
bullet Calculate T-alkalinity as:

         mg/L CaCO3 = ml of H2SO4 x 1000 / ml of sample

   3. Measurement of Hardness by titration (total hardness: T hardness):

bullet Add (2) scoops of hardness buffer to 50 ml of fresh test sample in a beaker and stir until dissolved.
bullet Add (2) scoops of hardness indicator to the sample in a beaker. Stir until dissolved.
bullet Fill a burette to the zero mark with EDTA titrant.
bullet Slowly add titrant to the sample while stirring until the red colour disappears and a blue colour appears. Calculate the hardness as:

            T hardness = ml titrant x 1000 / ml of sample

Results:

  1. Record all results in a table format.
  2. Discuss the significance of the results with respect to municipal water quality.
  3. Describe two alternative (direct or indirect) measurements of water quality.

Laboratory 8

Isolation of Caffeine from Tea Leaves

Introduction:

One important aspect of organic chemistry is the recovery and purification of compounds from natural sources. This laboratory will examine the recovery of caffeine from tea leaves, using extraction and sublimation procedures.

Caffeine is in the large class of compounds called alkaloids, which includes nitrogenous plant products that have a marked physiological action when administered to animals. The problem in recovering such products from a natural source is to identify the best method to remove the target compound from the background on contaminants, many of which may be quite similar to the target compound.

The properties of caffeine that will be exploited in this laboratory include solubility in hot water, solubility in methylene chloride at room temperature, and lack of formation of insoluble lead salts. As well, caffeine is basic and does not react with 5% NaOH as do the organic acids present in tea leaves.

Objective:

The objective of this laboratory is two-fold: to isolate caffeine from tea leaves, and to generate a schematic flow-chart describing the isolation and flow of both product and waste-streams. Many procedures in the Biochemical industry use similar flow-chart methods to describe their procedures.

Method:

  1. Boil 150 ml of tap water (with boiling chips) in a 600 ml beaker.
  2. Once boiling commences, add two tea bags and sustain the boil for 10 minutes.
  3. After 10 minutes, reduce the heat and remove the tea bags with tongs. Add 40 ml of 10% lead acetate and boil the mixture for 15 minutes.
  4. Prepare a slurry of 5 g Celite (filter-aid) in 20-30 ml water. Dampen a filter paper on a Buchner funnel and turn on the vacuum. Mix the slurry and quickly pour it onto the filter paper to form an even, dense cake. Discard the water in the filter flask.
  5. Vacuum filter the hot tea mixture until the filtrate is clear of particulate material.
  6. Evaporate the filtrate by boiling it in an open 600 ml beaker until the volume is reduced to about 50 ml. (If this concentrate is turbid, filter it again). Allow the solution to cool to room temperature.
  7. Solvent Extraction: Add 25 ml of methylene chloride to the cooled extract in a separatory funnel (ensure the stopcock is closed). In this solvent extraction the caffeine (and related impurities) are in the heavier phase. Note: do not shake too vigorously or an emulsion may form.
  8. Recover the methylene chloride layer into a clean beaker and extract the aqueous phase a second time with 20 ml of methylene chloride. Add this second methylene chloride extract to the first. Discard the aqueous phase.
  9. Extract the collected methylene chloride with 20 ml of 5% NaOH solution. (The caffeine remains in the methylene chloride phase.
  10. Extract the methylene chloride with 15 ml of cold water. Withdraw the methylene chloride and filter (conical funnel) into a clean, dry 150 ml beaker. Note: the filter paper in this step must be pre-wetted with a few drops of methylene chloride using a Pasteur pipette. (The methylene chloride will pass through the filter paper and any residual water will remain as droplets on the filter paper).
  11. In the fumehood with the door closed heat the filtered methylene chloride solution until all methylene chloride evaporates. The residue is caffeine. (Note: Pay Attention! once the methylene chloride evaporates the caffeine will sublimate off very quickly!)
  12. Collect and weigh the quantity of crude caffeine recovered.

Results:

  1. Prepare a
    schematic flow chart
    detailing the flow of caffeine and contaminants from start to finish. The type of steps and product flow must be identified but the quantities of additions, etc. can be omitted. The flow chart should have sufficient detail that if the quantities of components for the various steps were provided the flow-chart would provide clear work instructions.