CHM 235L
ORGANIC CHEMISTRY LABORATORY MANUAL
INTRODUCTION
This is a one credit laboratory course in the organic chemistry. Chemical synthesis and purification, structure determination, chemical kinetics, and chromatography are introduced in this lab. Emphasis is placed on record keeping, data interpretation, and report writing. It will be important to critically analyze data you collect to write a quality scientific report. The experiments will require you to prepare carefully in advance. Poor preparation could lead to mistakes ruining an experiment that took three weeks.
It is hoped that this lab will be both challenging and interesting. Your suggestions are welcome. If you would like to remain anonymous just drop your comments in the box for unknowns just outside the prep stockroom (216). Please write your course number on your comments. Information on grading, course requirements, and schedule is given in the course syllabus.
TABLE OF CONTENTS
INTRODUCTION I-l
CONCEPTS AND TECHNIQUES COVERED I-2
GUIDELINES FOR THE LAB NOTEBOOK I-3
GUIDELINES FOR SCIENTIFIC REPORTS I-5
Locker Check-out I-7
Planning I-7
Dropping Course I-7
Locker Check-In (Last Day of Lab) I-7
Video Tapes, Computers, and Calculation Checks I-8
SAFETY IN THE CHEMISTRY LABORATORY I-8
Chemical Labels and Hazard Codes I-9
Material Safety Data Sheets and Safety References I-11
Fume Hoods Use and Cleaning Glassware I-12
Fire Safety I-14
How to Protect Yourself I-15
What to Do in Case of Accident I-16
Hazardous Waste Disposal and Handling Reagents I-17
DATA RECORDING I-19
EXPERIMENTS
The Determination of Melting Range 1-1
Distillation and Gas Chromatography 2-1
Separation and Identification of Organic Compounds 3-1
(PRELIMINARY GRADING SHEET FOR THE LABORATORY NOTEBOOK)
Synthesis and Characterization of Isopentyl Acetate 4-1
Synthesis and Characterization of Cyclohexene 5-1
Determining the Reaction Mechanism of a Chemical Reaction Using Kinetics 6-1
Analysis by Thin Layer Chromatography 7-1
(FINAL GRADING SHEET FOR THE LABORATORY NOTEBOOK)
APPENDIX - Techniques A-1
Expt 1: Melting Points
Melting point characterization technique
Mixed melting point characterization technique
Expt 2: Distillation and Gas Chromatography
Simple distillation
Fractional distillation
Gas chromatography
Expt 3: Separation and Identification of Organic Compounds
Acid‑base concepts
Separation technique
Compound isolation and purification technique
Melting point characterization technique
Simple and vacuum distillation techniques
Infrared analysis
Expt 4: The Synthesis of Isoamyl Acetate (Banana Oil)
Dehydration of an organic acid and alcohol to make an ester
Simple Distillation
Infrared analysis verification of product compound ‑ principles and use
Percent yield determination
Expt 5: The Synthesis and Characterization of Cyclohexene
Alcohol dehydration to alkene
Reaction mechanism concept
Compound isolation and purification ‑ distillation
Percent yield determination
Infrared analysis verification of product compound
Gas chromatographic analysis of purity of product compound ‑ principles and use
Expt 6: Determining the Mechanism of a Chemical Reaction
Nucleophilic substitution concepts
Initial rates method of determining orders of reaction
Relationship between rate law and mechanism
Method of using varying solvent polarity to distinguish between first and
second order nucleophilic substitution
Expt. 7: Analysis Using Thin Layer Chromatography
Analgesics and Amino Acids
Thin layer chromatography - principles and use
Effect of solvent polarity and substrate structure
Introduction
The laboratory notebook record serves several purposes, the most important of which is to be the permanent, understandable record of data and observations taken during the laboratory period. A secondary, but less critical function is to serve as a record place for calculations and conclusions.
The method for keeping the notebook outlined below is based on the principles given above. Grading will be based on completeness and clarity, NOT ON NEATNESS. Write everything you do relating to this lab in your lab notebook. Write notes in it as you work such that you could understand what you did A YEAR LATER. NEVER USE SCRATCH PAPER.
Another important facet of scientific experiments involves the propagation of accuracy (or inaccuracy) of measurements (from the measurements and calculations to the final results.) Try to use the correct number of significant figures, as outlined in the Lab Manual, in collection of data and calculations. In this lab course always use at least 3 (three) significant figures in calculations.
Format of the Notebook
1. The notebook is to be a hardbound notebook-containing quadrille lined graph paper such as National #53-108 or #43-474. A spiral bound notebook is not acceptable.
2. You may use a notebook that has been previously used in another course, but please do not tear pages out of the notebook. Instead, start in a fresh portion of the book.
3. Number EVERY PAGE of the notebook starting with page 1 on the first "right-hand" page, page 2 on the next "left-hand" page, and so on, placing the numbers in the upper outside corners of the pages. The numbering of ALL pages should be done now, not as you start using each page. (If your notebook is already numbered in some other manner, please see the instructor.)
4. Write your name, ID number, instructor's name, class number (CHM 235L), and section letter on the front of the notebook.
5. Reserve the first two pages for a Table of Contents. One convenient form for the Table of Contents is:
Experiment 2 – Dipeptides pp. 4-11
Data pp. 5-6, 9
Calculations pp. 7, 8, 10
Conclusions (or Summary) p. 11
6. Do not tear pages out of a notebook.
1. It would be a good idea to have your notebook checked by your instructor or lab assistant at the end of the first few lab periods. He/she may want to sign and date the notebook at the end of the last entry to validate your day's work.
Data and observations
1. Record data as it is measured or observed in the laboratory. This record should be kept in order as it is taken--as a diary. Start on the top of page 5 on the first day and continue until that page is full (whether it takes 30 minutes or 3 lab periods). Do not leave blank spaces (more than 3-5 lines) on pages (That gives the impression that you are going to add something later after you have thought about it.) and do not leave any of the pages blank. If you jump from one experiment to another, record the data in the chronological (time) order that the data is taken, rather than trying to organize it by experiment (label new sections with titles).
2. Record all data and observations in ink. Never put these any place except directly into the notebook. If you make a mistake, cross it out with a single line--don't "obliterate" it or mark over it with the correction. If any correction is extensive (example: a whole trial has to be discarded) a simple statement of explanation should be given ("I dropped the beaker"). This will help you to remember what you did several weeks later.
3. Use only pens with permanent ink; do not use a pen with "erasable" ink or a pencil.
4. Place an identification of the experiment at the top of each page and at the start of each new lab period along with the date. Organize the written record by: a) identifying all data (example: "mass of beaker and acid"), b) giving units for all measurements, c) placing trials side by side so captions don't have to be repeated.
5. Do not include detailed instructions or procedures (such as those given in the Lab Manual) in the lab notebook. Include only enough of the procedure to keep the data from being confused (reference procedure, "page..."). Describe any changes made in the procedure, amounts of reagents used when the procedure in the Lab Manual has variable amounts, and observations you make that might be important in drawing conclusions. At the end of the lab period, it may be helpful to describe the status of the experiment so that you will be able to remember it at the start of the next period. The key is to make your lab notebook understandable to YOU and to SOMEONE ELSE who might need to read it.
Scientific Integrity
Scientific advances are based firmly on experimental observations and depend on the accuracy and honesty of the experimental data. The laboratory notebook must preserve the "sanctity" of data and observations--once the measurement is taken and recorded, it cannot be changed. "Dry-labbing" is totally unacceptable because it negates the very basis of the scientific method.
Conclusions and Calculations
Note: The treatment of calculations and conclusions is quite different than that of data and observations because calculations can always be checked or reconstructed, whereas an observation cannot.
1. The calculations and conclusions should be entered in chronological order. They should be entered in ink.
2. The calculations should be done each week in the notebook before you come to the next lab session and before you turn in the unknown report form for grading.
3. You need to show the step-by-step method of calculation for only one of a group of trials: then organize the results for all trials (including intermediate results as well as the final result) into some type of table. This will help you "sort out" the calculations.
4. As with data, do not skip more than 3-5 blank lines on a page as you work.
5. Place a heading on your calculations identifying the experiment and giving the data used in the calculations.
6. Include with the calculations: a) any necessary graphs, b) all results and conclusions, and c) any steps of reasoning and justification needed for the conclusions drawn.
7. At all times, attention should be given to the correct number of significant digits reported. However, intermediate results should be recorded with one more digit than warranted by the significance of the data. This process is explained in the section on significant figures later in the introduction.
GUIDELINES FOR SCIENTIFIC REPORTS
A scientific report should be a concise collection of YOUR observations, data, calculations, and conclusions for the experiment. It should not be a verbose collection of miscellaneous theory and discussion that has been taken from the literature or textbooks. Your goal in a report should be to inform the reader of what you wanted to do, of how you did it, of your results, and of your conclusions. If the reader is to be properly informed, the report should be readable, both grammatically and legibly.
Reports may have different forms depending on the information being conveyed. Many scientific reports are divided into six sections: abstract, introduction, experimental, results, discussion, and references. Below is a brief set of guidelines for each of these sections. Please note that it is not the only format used. Be sure to consult the class syllabus, information at the end of experiments in the laboratory manual, and the instructor with regard to more specific information relating to reports.
ABSTRACT: The abstract is a very brief summary of the experiment's objective(s), key experimental procedures, key results, and conclusion(s). It is very short and should not exceed half a page. The form and length of an abstract will vary greatly depending on the scientific journal, but the above guidelines are generally followed.
INTRODUCTION: The form and content of the introduction can vary greatly. In general it will give a short summary of background material introducing the specific objective(s) of the experiment. Most scientific reports will included some material covering the theory in the introduction. This material should convey to the reader an understanding of the theoretical bases for the experiment in a brief summary. In writing this section do not copy the laboratory manual or texts but summarize only the key points needed for understanding the experiment and then provide references for the reader. DO NOT get bogged down writing this section, rather keep it simple and short. Be sure to include any key chemical reactions, mechanisms and equations used.
EXPERIMENTAL: This section includes a brief discussion of the procedures and materials used in the experiment. The goal of this section should be to allow the reader to repeat the experiment. Since copying the procedure out of the laboratory manual would be a horrible waste of time, don't do it! Instead, write a short summary of the procedures used and reference the appropriate page numbers of the lab manual. Note any changes in the procedure if there were any. Often, specific information on the instrumentation and materials used is included in this section but you will not be required to provide such information.
RESULTS: The “results” section will include a summary of key data and results. Here are some helpful hints for writing a good results section:
1. Identify numbers present and use proper units.
2. Include complete tables and graphs but do not duplicate information. Be sure to identify columns or axes.
3. Use a reasonable number of significant figures for all numbers.
4. Give EXACT weights of solids and exact volumes of liquids used, if these are not listed in the lab manual.
5. List values for each trial and the median value if more than one trial is done. A comparison of values should give an estimate of your precision
6. Example calculations can be shown in the laboratory notebook and in the report (ask your TA for preference).
7. Present key results in a brief written form with clear, concise explanations.
DISCUSSION: The discussion section is the most important section of your report. In this section, the significance of your results should be analyzed. How did your results compare to the predicted outcome? What do your results mean? If the outcome was not as expected, describe the most probable sources of error (Be specific!). How could the results be improved? This should be the climax of your report so focus on this section! Be sure to use data, results, and equations to clarify and support your conclusions.
REFERENCES: A list of references might be known as the "Literature Cited" or "Bibliography". This section is very useful to an informed reader. A number which is elevated above the line or in parenthesis (1) can note references in the body of report. References should be listed in the order they are first used in the report or you can use other reference formats, which are common in scientific literature. Example references:
(1) Stewart, J.E., "Infrared Spectroscopy," Marcel Dekker, Inc., New York, 1970, pp. 519, 520.
(2) Worley, J.D., J. Chem. Educ., 46, 608, (1969).
An excellent guide for writing scientific papers is the "Handbook for Authors of Papers in American Chemical Society Publications" published by the American Chemical Society. This is a must for any chemistry major and can be purchased at the NAU bookstore. It is not however required for this course. Simply reading articles in scientific journals is an excellent way to become familiar with the form of scientific reports and indeed one of the assignments for this course will require you to do just that. In any case please remember that a report does not have to be long to be good. A short, concise report clearly stating the needed information is much better than a long verbose report filled with unneeded information.
Locker Check-Out
When you check out your locker, your teaching assistant (TA) will provide you with a locker list and a key. The section on safety should be read before starting. First put on safety goggles. You should check and make sure all your equipment is present and undamaged. Have your TA fill out a requisition form for any broken or missing items. Take the requisition form to the prep stockroom window (216). When you're sure your drawer is complete, finish filling out your locker list, sign it and make sure the safety exercise on the back of the locker list is complete and give it to the TA. You will then be responsible for the contents of your drawer. The equipment in it is worth over $200.00 so keep it locked and keep the key in a safe place like on your personal key ring. If you lose your key it can be replaced for $50.00 (see your teaching assistant). If you break anything you may replace it at the stockroom window. You must bring your student ID card and you will be billed for the broken item. A lost and found is kept in each laboratory for lost equipment and in the prep stockroom for personal items.
Planning
In this laboratory it is very important to use your time wisely. Here is some advice from past students: "Be prepared before you come to lab. Read over material carefully until you understand what is expected." "Don't get behind," "Go to every lab, don't leave early and don't waste time," "Budget time wisely" "Read experiment before coming to lab." This is excellent advice and if you follow it, you will have more than enough time to complete all the experiments.
Dropping Course
You must check-in your locker before drop or withdrawal from the lab. You should check-in your locker during your regularly scheduled lab period. If this is not possible go to the stockroom window (216) for help. There will be a $30.00 service charge if a locker is not checked in by the middle of the last scheduled lab period for your section. There will be a $50.00 charge for each key not returned. To check-in your locker, see your lab TA to obtain your locker list or go to the stockroom (216) for help. Follow the instructions below to check-in your locker. If you did not use your unknowns, please return them to the stockroom (216) without washing the unused vials. Please wash out the used vials as noted below. When you are finished, take your locker list and locker key to the stockroom (216) or your TA.
Locker Check-In
1. Fill out the online lab evaluation and then obtain your locker list from your TA.
2. Empty the drawer and scrub it out with a wet sponge at the sink. Clean dirty glassware and used unknown vials (remove all labels.) Replace any missing or broken item at the chemistry stockroom (216). Be sure to bring your student ID card with you.
3. Take your clean unknown vials, unused unknowns, and locker list to the stockroom (216). The stockroom employee will take the vials and initial your locker list. Your locker list must have the stockroom’s initial for you to continue check-in.
4. Set your equipment out on the bench in the order listed on your locker list (use a locker outline if available.) Notify the TA that you are ready to check-in your locker. You may have to add your name to the bottom of a list on the whiteboard.
5. If the locker is in order, the teaching assistant will lock your drawer and sign and date your locker list. Put any extra items in the lost and found box in the lab. Be sure the TA has your signed locker list and key(s) or you may be charged a $30.00 locker check-in fee and $50.00 per key not returned. If you are dropping the lab, take your locker list, key(s) and equipment outline to the stockroom (216) if the TA is not available.
6. Before you leave, check your grades posted online and the teaching assistant's grades to be sure your grades are correct.
7. If you do not check-in your locker on or before your last regular laboratory meeting, you will be charged a $30.00 check-in fee and a $50.00 charge per key not returned. The key fee may be refundable if you return your key to the laboratory manager in 212 or the stockroom manager in 214.
Video Tapes
There are videos on the use of the balance, pipettor, and other lab equipment posted on the “Instructional Labs Homepage” at: http://jan.ucc.nau.edu/~jkn/Labs.html The computers located in room 221 and 207 and may be used to view these videos.
Computers
There are computers and programs such as graphical analysis, ACD structure drawing, etc. useful for some experiments. The computers are available the same hours as the video tapes in room 207 and 221. If you have problems using them, ask your TA for help.
SAFETY IN THE CHEMISTRY LABORATORY
Laboratory safety involves the prevention of and response to laboratory emergencies. Good prevention is far better than someone getting hurt. This begins with always being aware of chemical and laboratory hazards. Hazard codes, chemical labels, and material safety data sheets are the first sources of information that help us prepare to work safely in a laboratory. This information can be used to do risk assessment on the hazards and precautions for the experiment you are about to do. Certain rules need to be followed to keep you safe and you must know what to do in case of an emergency. Chemical waste management is another important aspect of a safe laboratory and a key regulatory compliance issue.
Risk Assessment
A risk assessment determines what hazards will be encountered during an experiment or lab procedure, how to mitigate them (precautions such as goggles or gloves), and what should be done if something goes wrong. There may be physical or chemical hazards present that will be discussed in the experiment write up. Chemical hazards will be expressed using hazard codes and/or special warning stickers on bottle labels. If you observe a 3 or 4 in the hazard code you may want to obtain more information by referring to the material safety data sheet (MSDS) and note hazards and how to respond to them. For every experiment you must write a risk assessment and outline the experimental procedure before you start lab work.
Chemical Labels and Hazard Codes
The first source of information is the label on a chemical bottle. Read the label carefully before using a chemical. A commercial chemical bottle will have extensive information on the label such as the chemical name and formula, physical properties, purity, molar mass, hazards, safety precautions, suggested protective equipment, and other information. A hazard code may also be included on the label.
The chemistry department has adopted the “Baker” hazard code classification system to inform users of potentially hazardous chemicals. This system is designed to provide information to people who handle chemicals in laboratories. Hazards are classified according to four types: health (toxic), flammability (fire), reactivity (explosive or reactive), and contact (corrosive). The intensity of the hazard is indicated by using a number from "0" (no hazard) to "4" (extreme hazard). This information is conveyed using either a four-colored label found on "J.T.Baker" chemical products or as a series of four digits. The label on chemical bottles may look like this:
The four-digit hazard code used in the lab manual would look like this:
1321
For example, the code listed above for acetone indicates a slight health hazard (1), a high flammability hazard (3), a moderate reactivity hazard (2), and a slight contact hazard (1). Hazard codes will be listed after the chemical inside parentheses: (1321)
The "Baker Codes" for each of the four hazards are defined according to the following scheme:
HEALTH (BLUE): Toxic effects of a substance if inhaled, ingested or absorbed.
0. No Hazard
1. Slight hazard
2. Moderate hazard
3. Severe danger
4. Deadly, Life Threatening
FLAMMABILITY (RED): Tendency of a substance to burn based on flash point or the temperature a substance will burn when exposed to a spark.
0. Will not burn
1. Flash point above 200°F
2. Flash point from 100-200°F
3. Flash point from 73-100°F
4. Flash point below 73°F
REACTIVITY (YELLOW): Potential of a substance to react violently with air, water or other substances.
0. Stable.
1. Reacts under elevated temperature or when in
contact with other substances under other than normal working conditions.
2. Reacts violently but will probably not explode
under normal working conditions.
3. Reacts violently or explodes under normal working
conditions when in contact with air, water or other substances.
4. May react violently or detonate spontaneously under
normal working conditions.
CONTACT (WHITE): The danger a substance presents when it comes in contact with skin, eyes or mucous membranes.
0. No contact hazard to normal, healthy tissues.
1. Slight hazard; irritant to sensitive tissues,
Avoid contact with eyes and mucous membranes.
2. Moderate hazard; irritant to sensitive tissues,
damages tissues.
3. Severe danger; destroys tissues, including skin.
4. Extreme danger; life threatening.
The National Fire Protection Association (NFPA) is a hazard code system that was adopted in 1975 to communicate hazards to emergency responders. This system uses a label that you may be familiar with since it appears on entrances to stores containing hazardous chemicals and on chemical containers. The NFPA may differ from the “Baker” code since it provides information to firefighters while the “Baker” code provides hazard information in a laboratory situation. The codes are very similar except the white section in the NFPA code refers to special or specific hazards of importance to firefighters such as “ox” for oxidizing agent.
Health Hazard (Blue) - Degree of hazard for short term protection
0. Ordinary combustible hazards in a fire
1. Slightly hazardous
2. Hazardous
3. Extreme danger
4. Deadly
Flammability (Red) - Susceptibility to burning
0. Will not burn
1. Will ignite if preheated
2. Will ignite if moderately heated
3. Will ignite at most ambient conditions
4. Burns readily at ambient conditions
Reactivity, Instability (Yellow) - Energy released if burned,
decomposed, or mixed
0. Stable and not reactive with water
1. Unstable if heated
2. Violent chemical change
3. Shock and heat may detonate
4. May detonate
Special Hazard (White position on diamond)
OX. Oxidizer
W. Use no water, reacts!
The hazard codes are given only as a guide to warn the user of probable hazards and to approximate the degree of hazard under normal use. The user must not be lulled into a false sense of security by a low number on the label, but must take full responsibility for safe use of the chemicals. Avoid over-reliance on hazard codes. Refer to the Material Safety Data Sheets (MSDS) and other safety information whenever you are working with chemicals that are unfamiliar to you. This is especially important when mixing chemicals. Chemicals with relatively safe hazard codes can become dangerous when mixed with other chemicals.
The Material Safety Data Sheet (MSDS) should be read to obtain additional safety information before the chemical is used. These sheets are available in Room 212 for all chemicals used in the chemistry department; they must not be removed from that room. The internet is a great resource for MSDS and general safety information.
MATERIAL SAFETY DATA SHEETS AND SAFETY REFERENCES
Often the label on a chemical container does not provide enough information on a chemical to use it safely. Additional facts on chemical hazards can be found in material safety data sheets, safety references, and chemical/safety catalogs. A safety library is maintained in room 212. Material Safety Data Sheet (MSDS) for every chemical purchased by the chemistry department are maintained and use of these sheets is encouraged. Aldrich/Sigma MSDS volumes are also available. Links to MSDS information can be found on the web under course information on chemistry instructional labs homepage. Other references on laboratory safety, hazardous chemicals, carcinogens, chemical first aid, exposure limits, hazardous waste disposal, etc. are also available. The following references can be found in room 212.
a) CRC Handbook of Laboratory Safety
b) "Dangerous Properties of Industrial Materials" by Sax
c) Toxic Substances List (NIOSH)
d) Annual Reports on Carcinogens
e) Emergency Response Guide
f) "First Aid Manual for Chemical Accidents" by Lefevre
g) The NAU Chemical Hygiene Plan
h) "Safety in Working with Chemicals" by Green and Turk
i) NIOSH/OSHA Pocket Guide to Chemical Hazards
Free sources of information such as chemical catalogs (the Aldrich and Flinn catalog are good references) and safety catalogs can provide information such as the right choice of gloves for a certain class of hazardous compounds. Room 212 is open Monday through Friday from 8:00 am to 5:00 p.m. to make this safety material more available. This material will be removed from 212 for making copies and then only for 30 minutes or less.
The Material Safety Data Sheet (MSDS) provides technical, chemical, physical, and hazard information for the "hazardous material." The "Hazardous Material" may be an individual substance or a mixture of hazardous ingredients. The Occupational Safety and Health Administration (OSHA) requires manufacturers to prepare an MSDS for each hazardous substance they make. While OSHA is very specific about the information that must be provided in an MSDS, they do not require manufacturers to provide the information in a certain format. Therefore, the order in which information is provided in a MSDS may vary from manufacturer to manufacturer. The following is an outline of the content of a MSDS, but not necessarily in the order provided by all manufacturers:
A. Material Identification and Hazardous Components
B. Physical/Chemical Characteristics - vapor pressure, flash point, etc.
C. Fire and Explosion Hazard Data - auto ignition temperature, extinguishing media, etc
D. Reactivity Hazard Data
E. Health Hazard Data
F. Control and Protective Measures - the type of personal protective equipment and type of ventilation to be used, and the precautions to be taken when using the material for its intended purpose is given
G. Precautions for Safe Handling and Storing - use/leak procedures
Please note that more sections and more information may be provided by the individual manufacturer; however, the information required in the listed sections MUST be found in a MSDS. While all of the information in the MSDS is important, the information on the information on safe handling, control and protective measures, reactivity/health hazards, and extinguishing media is very important. When using a MSDS keep in mind that the target audience is assumed to be a chemical worker using larger amounts of the material than you will encounter. The personal protection measures may sometimes need to be modified for a laboratory situation where much small amounts are used in a more controlled environment. For the safety of yourself and those people you work with, be sure to read the MSDS on any chemical you work with. BE INFORMED! Read labels and use care when using concentrated reagents.
FUME HOODS
The building is equipped with state-of-the-art low flow fume hoods. You need to know how use them correctly. First of all, every hood is equipped with a flow sensor and alarm. If the flow is too slow or too fast they may not be able to trap and remove fumes and an alarm will go off. Notify your TA or instructor immediately if this is the case. The fume hood has two modes, standby or sleep mode and normal mode. When the sash (front window of the hood) is all the way down or closed the hood will be in standby mode and the flow rate will be about half of normal mode to conserve energy. If you pull the sash up about an inch or less you will hear a click and the hood flow will ramp up to normal mode and provide you with the best protection. The sash has sliding windows that can be used to protect you and provide access to work inside the hood with the sash closed. The hood may not function correctly with the sash all the way up. Also never store chemicals or equipment in a fume hood because this can degrade fume hood performance. Keeping this information in mind follow these rules for safe fume hood use:
· Never put you head inside a fume hood.
· Keep the sash down except when setting up an apparatus.
· Before using pull sash up just enough to ramp up to normal mode (<1”).
· Use sliding windows to access work in hood. When doing dangerous work keep a window in front of you for protection and reach around it to work.
· As a general rule you should work at least 6 inches inside a hood from the hood sash.
· Notify the TA or instructor immediately if an alarm comes on.
· Clean up any spills immediately. Get the TA’s help if the spill may be dangerous.
· When done working in a hood, wipe down with a damp sponge, push the sash all the way down, close the sash windows, and turn off the light.
· Never store chemicals and equipment in the hood. Instead use your bin or locker for your solutions or for other stuff the storage cabinets under or to the side of the hood. It’s ok to leave ring stands and rubber tubing for condensers in hood.
CLEANING GLASSWARE
First of all use proper gloves to protect your hands if needed. To properly clean glassware you need to be aware of the hazards and solubility properties of the material that was used. Be sure to properly dispose of any used chemicals if they pose a hazard. You may need to dispose of any residual material in a container if it poses a significant hazard. Containers used for volatile concentrated acids such as hydrochloric, nitric, or acetic acids or bases such as concentrated ammonium hydroxide must be rinsed in a fume hood with water to remove any residual chemical.
Water soluble materials such as ones used in general chemistry labs can often just be rinsed with hot tap water several times and then once with RO water (purified water). Fill a wash bottle with RO to rinse glassware or use the RO rinse tub in you lab. Do not use the RO water tap in you lab to rinse your glassware. Wash glassware soon after you are done using it and never leave or store dirty glassware. If need be use lab soap to help clean glassware. Hard to clean glassware such as volumetric or mohr pipets may need to be cleaned with soap in a sonicator. Sometimes with less water soluble materials you will need to use a cleaner such as simple green. This works very well with labels.
When working with volatile organic chemicals, containers may need to be rinsed with acetone in a fume hood to remove the organic material before washing at a sink. Our organic chemistry labs will have at least one acetone cleaning station in a fume hood. Never allow fumes from a volatile chemical to escape into the lab. Some organic material such as vacuum grease is insoluble in both acetone and water. Use hexanes to remove this material and then acetone to remove the residue hexanes. Collect used acetone and hexanes in a waste bottle. Do not add any other materials to these bottles.
FIRE SAFETY
Using extinguishers:
In most chemistry laboratories there is a fire extinguisher, eyewash and safety shower, first aid kit, and other safety equipment. To use an extinguisher:
a. Select proper extinguisher for fire (explained later)
b. Twist pin and pull
c. Hold the extinguisher in upright position and aim the
hose or bell at base of the flames from a distance
d. Squeeze handle until extinguishing material is released
e. Slowly approach fire sweeping the base of the flames
f. Continue until fire is out
g. Continue to watch for auto ignition even after fire appears out
h. In summary remember "PASS"; Pull, Aim, Squeeze, Sweep
Three Components of Fire:
Fire burns because three components are present- heat, fuel and oxygen. Fire is a chemical reaction. It happens when a material unites with oxygen so rapidly that it produces flame. Think of fire as a triangle. If any one of the three sides, heat, fuel or oxygen is taken away, the fire goes out. This is the basis for fire extinguishment. Heat can be taken away by cooling, oxygen can be taken away by excluding air, fuel can be removed to a place where there is no flame, or a chemical reaction can be stopped by inhibiting the oxidation of the fuel.
Cooling a fire calls for the application of something, which absorbs heat. Although there are others, water is the most common cooling agent. Water is commonly applied in the form of a solid stream, finely divided spray or incorporated in foam.
Often, taking the fuel away from a fire is difficult and dangerous, but there are exceptions. Flammable liquid storage tanks can be arranged so their contents can be pumped to an isolated empty tank in case of fire. When flammable gases catch fire as they are flowing from a pipe, the fire will go out if the flow can be valved off.
Oxygen can be taken away from a fire by covering it with a wet blanket, throwing dirt on it or covering it with chemical or mechanical foam. Other gases which are heavier than air, such as carbon dioxide, or a vaporizing liquid can be used to blanket the fire, preventing the oxygen from getting to the fire.
Studies made during recent years have indicated that the familiar statement, "Remove heat, remove fuel or remove oxygen, to extinguish a fire" does not apply when dry chemical or halogenated hydrocarbons are used as the extinguishing agents. These agents inactivate intermediate products of the flame reaction resulting in a reduction of the combustion rate [the rate of heat evolution] and extinguishing of the fire.
Four Classes of Fires:
CLASS ["A"] fires occur in ordinary combustible materials such as wood, cloth and paper. The most commonly used extinguishing agent is water, which cools and quenches. Special dry chemicals also extinguish fires in these materials for use on Class A, B and C fires. These provide a rapid knock down of flame and form a fire retardant coating, which prevents flash.
CLASS ["B"] fires occur in the vapor-air mixture over the surface of flammable liquids such as grease, gasoline and lubricating oils. Flammable liquids always generate vapor due to their high vapor pressure. When mixed with air and contacted by an ignition source, it is the vapor, not the liquid, which burns. The fuel vapor and oxygen provide two sides of the fire triangle. A flammable liquid is usually more dangerous when temperatures are high because more vapors are generated. The lowest temperature at which a liquid still has enough vapor pressure to give off enough vapors to form a flammable mixture with air is called the flash point.
A smothering or combustion inhibition effect is necessary to extinguish Class "B" fires. Dry chemical, foam, vaporizing liquids, and carbon dioxide all can be used as extinguishing agents depending on the circumstances of the fire.
CLASS ["C"] fires occur in electrical equipment where non-conducting extinguishing agents must be used. Dry chemical, carbon dioxide, and vaporizing liquids are suitable. Because foam, water (except as a spray), and water-type extinguishing agents conduct electricity, their use can kill or injure the person operating the extinguisher, and severe damage to electrical equipment can result.
CLASS ["D"] fires occur in combustible metals such as sodium, potassium, lithium, magnesium, titanium, or zirconium. Specialized techniques, extinguishing agents and extinguishing equipment have been developed to control and extinguish fires of this type. Normal extinguishing agents generally should not be used on metal fires as there is danger in most cases of increasing the intensity of the fire because of a chemical reaction between some extinguishing agents and the burning metal. Since the Chemistry Department doesn't have a Class "D" fire extinguisher, dry sand or graphite can be used to smother Class "D" fires. Buckets of dry sand should be provided in labs where Class "D" fire hazards are present.
How to Protect Yourself
1. Eye Protection MUST BE WORN IN THE LABORATORY AT ALL TIMES unless otherwise notified by the instructor or TA. Avoid rubbing your eyes in lab unless you wash your hands first. Use extra caution when using corrosive chemicals. Indirectly vented or nonvented goggles are the required eye protection for this lab course. Safety glasses or directly vented goggles are not acceptable. Do not modify or remove the vents on goggles. Write your name and section letter on your goggles.
2. Skin protection should be employed where appropriate; you may be required to wear long pants. Avoid wearing shorts. The use of a lab coat or plastic apron is recommended. Closed toed shoes must be worn at all times in the laboratory for protection against broken glass and spilled chemicals. Open-toed shoes or sandals are not appropriate footwear in lab areas. Disposable gloves are available for the handling of hazardous chemicals. Always remove them before exiting the lab. After completing lab work for the day, wipe down your entire work area (or any area used include balance, fume hoods, or reagent areas) with a clean damp sponge to clean up any spilled chemicals and other material. Rinse out the sponge several times and wring it out. Wash your hands as you exit the lab.
3. Protection from fumes or fine powders: Never allow hazardous chemical fumes or dust to escape into the open room; use fume hoods when necessary or specified. Be sure to use the fume hoods correctly, following the instructions provided by your TA or instructor. Avoid putting your head inside the fume hood and close the sash or fume hood window when it is not in use.
4. Protection from internal poisoning: Never "pipet by mouth", eat, drink, or smoke in the laboratory. These activities are prohibited. Wash your hands after you have completed lab work or leave the lab room.
5 Protection from hot surfaces: Use the appropriate types of tongs to handle hot objects. Test tube holders are too weak for carrying flasks.
6. Protection from fire and explosion: Never allow flammable vapors to escape into the open room (see No. 3). Ether is especially dangerous in this respect. Never use an open flame while flammable liquids are being used in the room. Hot plates should be used with care, as they are an ignition source. Flammable volatile liquids should be used in fume hoods and stored in solvent cabinets when possible. Long hair should be tied back to keep it away from open flames.
7. Protection from cuts: When manipulating glassware or ceramic ware, protect your hands with a cloth towel. Clean up broken glass immediately. Do not pick up broken glass with bare hands. Use a broom and dustpan to dispose of glass in the "Broken Glass Container". Do not clean up broken mercury thermometers without help from your TA since mercury requires special disposal procedures.
8. Protection from the unexpected: Always read all labels noting the chemical name, formula, concentration, and warnings (including hazard codes) carefully and double check to make sure you have the correct chemical and concentration. Follow directions in the experimental procedure exactly. Remove obstacles by keeping lockers closed, lab stools out of aisles, and backpacks and coats stored on coat rack. For unassigned lab work, you must have the approval of the instructor. Carefully follow hazardous waste disposal instructions given later.
9. Safety Violations: Any student who does not follow the above guidelines will be given one warning and will then be removed from the lab for the day for any subsequent violations. There may also be grade deductions or permanent removal from the lab for serious violations.
What to Do In Case Of Accident
1. During your first lab period, locate the position of the fire extinguishers, eyewashes, safety shower, first aid kit, phone, fire alarm pull stations, exits, hallway showers, and any other safety equipment.
2. In all cases of accident or injury, notify the TA and the instructor.
3. For any serious fire or injury: Call the POLICE DEPARTMENT (33000) from any campus phone. Security is in the best position to summon fire or ambulance service. Call the Flagstaff Fire Department (8-774-1414) or dial 8-911 if Security cannot be reached. Use the FIRE ALARM PULL STAIONS (red box by every stairwell entrance) to clear the building of personnel. THE LOCAL FIRE ALARM IN THE LAB BUILDING WILL SUMMON HELP BUT STILL ALWAYS CONTACT CAMPUS SECURITY FROM A SAFE LOCATION. Students should stay with their lab TA as the building is evacuated if it is safe to do so.
4. In case of a small fire: Immediately get help from your TA or instructor. Fire extinguishers are rated for ABC type fires in chemistry where A is combustible (paper, etc.), B is flammable liquids, C is electrical, and D is combustible metals. Use dry sand for D type fires or a special extinguisher rated for these fires. To use an extinguisher remember “PASS”: Pull the pin, Aim the hose, Squeeze the handle, and Sweep the base of the flames. If a person's clothing is on fire, they should immediately stop-drop-roll, use the safety shower if it is close, or smother the fire with a lab coat or fire blanket. Cover beaker fires with a watch glass or larger beaker to remove oxygen and put out the fire. Cool minor burns in cold water immediately.
5. In case of chemical contact: If the area of contact is small, flush it well under the nearest water tap for 15 minutes. Eyes must be flushed immediately using the eyewash at one of the sinks or the eyewash by the safety shower keeping the contaminated eye(s) open. In case of large areas of contact, start rinsing the person using the safety shower and remove contaminated clothing. After decontamination, the person will be taken to a shower room by the prep stockroom where rinsing will continue for at least 15 minutes or until EMS arrives if called. Immediately inform the instructor or TA in any case.
6. In case of mercury spillage: To dispose of this hazardous material properly, notify your TA and he or she will collect the mercury using a special spill kit.
7. Chemical spill: If only a few drop of chemical are spilled, immediately clean up the material with a damp sponge and rinse out the sponge well at a sink and wipe down the area a second time with the rinsed out sponge. In case of a larger chemical spill immediately notify your TA and ask for help. Sodium bicarbonate (baking soda) can be used to neutralize acid spills. If the substance spilled is flammable, turn off all burners, hot plates, or electrical devices and get help from your TA. For large spills notify the instructor, the laboratory manager, or the stockroom manager. Clean-up materials are available in the lab or stockroom.
Hazardous Waste Disposal
The Resource Conservation and Recovery Act (RCRA) mandates the proper disposal of hazardous waste. Disposal of many waste chemicals by putting them down the sink is now illegal. Regardless of regulations, the proper management of hazardous waste is of particular importance to the people of Arizona where the contamination of groundwater by hazardous waste could have grave consequences. Please carefully follow the instructions below to protect our groundwater and keep your lab safe. Hazardous waste is determined by four properties:
TOXIC: A poisonous substance, potentially harmful to human health, can cause cancer or birth defects, or can contaminate, harm or kill wildlife.
FLAMMABLE: substances, which can explode, ignite, or emit toxic gases or fumes if exposed to a source of ignition.
REACTIVE: An unstable substance which can react spontaneously if exposed to heat, shock, air, or water. Reactions may include fires or explosions. The research director or instructor for the lab must neutralize any reactive substance before it can be accepted for disposal.
CORROSIVE: A substance that could corrode storage containers or damage human tissue upon contact. (For example, acids and bases, pH <4 or >10)
Chemical waste that does not fit into the above categories may be flushed down the drain with large amounts of water. The instructor or TA must be consulted if there is uncertainty with regard to the collection of a chemical waste.
All waste bottles are labeled and color-coded with tape. The label will include an experiment number and a hazardous waste description that will help you decide which bottles to put your waste into. Find the correct waste bottle for your experiment number and for the type of chemical waste you have; make sure the description of the composition fits the waste you are adding to the bottle. Using the wrong waste bottle could create a safety hazard and will be treated as a safety violation. The following table should help. Some nonhazardous chemical waste from experiments you do may be put down the drain. Avoid using cup sinks or water troughs to dispose of chemicals, instead use large sinks in the lab. Acidic or basic used chemicals (pH <4 or >10) will be disposed of by neutralization in a fume hood. Waste bottles may also be color-coded using the following scheme:
Blue - health hazard, poison
Red - flammable hazard, organic liquid
Yellow - reactivity hazard (strong oxidizers, etc.)
White - contact hazard, corrosive
Orange- low hazard materials with hazard codes of 2 or less
Handling Reagents and Standard Procedures
The liquids, solids, and solutions used in a laboratory are called reagents. You must become well acquainted with these reagents, their containers, and their proper use. The reagents are kept on a separate bench away from your work area. Some reagents, such as flammable liquids must be kept in the fume hood because it generates flammable fumes. The reagents are put out need for each experiment, starting with Experiment 1 and ending with Experiment 7. When you need a reagent please follow these rules:
1. Be sure to use the correct reagent, especially noting the concentration. Find the reagent, check the concentration, and then carefully read the label again to be sure you have the right one. Note the hazard code and take necessary precautions.
2. Use the reagent at the reagent bench. Do not take the reagent container to your work area.
3. Please conserve and take only what you need.
4. Do not contaminate the reagents. Always use a clean spatula for solids and clean glassware for liquids. Never put a pipet or pipettor into a liquid reagent, instead pour what is needed into a clean, dry container and take it to your work area.
5. NEVER return unused reagents, liquid or solid, to the reagent bottles. Discard or share any excess.
6. Put lids back on the reagent containers snugly and put back in correct locations.
7. Clean up any reagent you spill with a wet sponge, rinse out the sponge at the sink, and then wash your hands.
8. Use great care with corrosive chemicals (strongly acidic or basic solutions). Always wear safety goggles! Rinse your hands with tap water after using corrosive chemicals, especially if you feel a burning or slimy sensation on your skin. Wear the gloves provided in the laboratory if called for. Most strong acids and bases will be disposed of as a “Corrosive Liquids” in the hood as noted in experimental procedures unless the used chemical has other hazard properties.
9. Avoid using cup sinks to dispose of nonhazardous chemicals, instead use large sinks available in the lab. Be sure to follow the instructions in the experiments with regard to the disposal of chemicals.
10. Wash all glassware that you use. Often all that is needed is to rinse well with hot tap water 4 or 5 times. If the glassware is really dirty use detergent or simple green, then rinse hot tap water. Rinse all glassware with RO water (use RO rinse tube if one is available in your lab). Test tubes, pipets, buret, and volumetric flask should also be rinsed with a small amount of fresh RO water before storage. Fill your plastic wash bottle with RO water for doing this. You do not need to dry the inside of glassware. Never store dirty glassware!
11. Hot objects can damage the lab bench surface. Never put hot objects on the bench top, instead place hot objects on the ring stand base or white hot pads provided.
12. Flammable or volatile chemicals must always be used in a fume hood. Stopper containers containing them when transporting them outside fume hoods. Rinse out glassware used to work with these chemicals in the waste hood before washing them in the sink.
13. At the end of every lab period you must clean your workstation bench space, hood space, and any area you used by wiping it down with a clean, damp sponge. Rinse out and wring out the sponge when you are done. Your workstation drawer must be neat and complete with clean equipment. Your locker must have no extra equipment.
Recording Experimental Data Using Correct Significant Figures
It is important to take data and report answers such that both the one doing the experiment and the reader of the reported results know how precise the final answer is. The simplest, way of expressing this precision is by using the concept of significant figures where a significant figure is any digit that contributes to the accuracy of an experimentally measured number or to a number calculated from experimentally measured numbers. Please refer to the chemistry textbook for a discussion of the use of significant figures.
This laboratory course emphasizes learning the precision of the glassware and the balances. A larger number of significant figures can and should be carried when you are using a volumetric pipet or flask, pipettor, or buret than when you are using a beaker, erlenmeyer flask, or graduated cylinder. Different equipment in the laboratory is used to achieve different levels of precision. For example, the volume of a liquid sample can be measured using different types of glassware, some of which are more precise than others. This is shown in the following table.
|
|
Precision of Volume Measurement |
|
Equipment |
for Various Equipment |
|
250 mL Beaker |
±10 mL |
|
250 mL graduated cylinder |
±1 mL |
|
100 mL volumetric flask (class A) |
±0.08 mL |
|
25 mL graduated cylinder |
±0.2 mL |
|
10 mL measuring pipet (Mohr) |
±0.05 mL |
|
25 mL buret |
±0.02 mL |
|
5 mL, 10 mL volumetric pipet |
±0.01 mL |
When an approximate volume is needed, a beaker or graduated cylinder will be used, but when an accurate volume is needed, a pipet or buret will be specified for use. Recognizing when to make an accurate measurement and when to be satisfied with an approximate measurement can save much time. Frequently, the written directions will give clues to the needed precision by using the words "approximately" or "about" when the precision is not important and "exactly" or "precisely" when the precision is important. Another clue would be the number of significant figures used to write a number. For example, a volume of 10.00 mL would require the use of a 10 mL volumetric pipet or pipettor to measure the desired volume. On the other hand, a volume expressed as “about 10 mL” would require only a small beaker or graduated cylinder to measure the volume. It is also important to note that glassware used for accurate measurements is calibrated at a specific temperature, which is noted on the glassware.
When a measurement is made, the question arises: "How many digits or figures should be recorded?" The answer is straightforward: For a measured number record all digits, which are known with certainty, and the last digit, which is estimated. Many of the measurements in this course involve the estimation to the nearest one-fifth or one-tenth of a scale marking. For example, in Experiment 5 a 25mL graduated cylinder, which has scale markings every 0.5 mL, should be read to the nearest 0.1 mL, estimation to the nearest one-fifth of a division. The graduated cylinder does not need to be used to this accuracy at all times:
NOTE: Whenever estimation between markings is being done and the reading is "on the mark," the last digit should be included to convey the idea of accuracy to the reader. For example, with a buret, which has markings every 0.1 mL, a reading on the mark of 11.3 mL would be recorded as 11.30 mL; otherwise, the reader will not know that the buret was really read to the nearest 0.01 mL.
Reporting Answers in Addition and Subtraction
When experimental data have been recorded correctly, the uncertain or estimated digit is the last digit. The calculated sum or difference of experimental measurements must be carried out only to the place where the first digit of uncertainty enters the calculation.
Example: Add 14.75, 1.475, and .001475 (all of which are experimental numbers). The digits of uncertainty are underlined.
14.75
1.475
0.001475
--------------
16.226475
Since the answer may include only the first digit of uncertainty, it should be rounded off to that digit and reported as 16.23. It helps to line the numbers up by the decimal point.
Reporting Answers in Multiplication and/or Division
1. All measurements should be recorded to the appropriate number of digits as discussed in the section on recording experimental data.
2. The position of the decimal point is ignored in counting the number of significant figures.
3. All digits except zero are always significant.
4. Zeros may or may not be significant. Any zero to the left of the first non-zero digit is never significant (0.0256 has 3 significant figures because neither zero is significant).
a. Any zero to the right of the first non-zero digit is always significant if there is a decimal point (2.5070 has 5 significant figures since both zeros are significant).
b. If there is no decimal point, zeros to the right of non-zero digits are significant unless it is stated otherwise (the number 25000 has 5 significant figures unless some other precision is stated, such as 25000 ± 100). Numbers with "trailing" zeros (zeros to the right of all other digits) should be written in standard exponential form to remove questions (2.50 x 104 has 3 significant figures; 2.5000 x 104 has 5 significant figures).
In multiplication and/or division, the answer should be reported to the same number of significant figures as the value in the computation with the least number of significant figures.
Example: Find the answer to the following multiplication/division problem to the correct number of significant figures.
0.085 has 2 significant figures; 0.08206 has 4; 366 has 3; and 0.782 has 3. A calculator shows the answer to be 22.989865, so the answer should be reported as 23.
Interpretation of Data
Significant figures are excellent to express the precision of raw data but not always so good to express the precision of calculated values. As a general rule in this laboratory course you should always use at least four significant figures for calculated values to avoid rounding errors. Once the final answer is calculated, it can be expressed using correct significant figures. In order to interpret how good your results are, certain terms need to be understood. You will need to understand the following definitions.
1. Accuracy: The term "accuracy" describes the nearness of a measurement to its accepted or true value. In CHM 151L, the accuracy of your work becomes known when your unknown is graded. A PASS grade indicates good accuracy, a PARTIAL CREDIT grade indicates marginal accuracy, and a REPEAT grade indicates that your results had poor accuracy.
2. Precision: The term "precision" describes the "reproducibility" of results. It can be defined as the agreement between the numerical values of two or more measurements that have been made in an identical fashion. Good precision does not necessarily mean that a result is accurate.
3. Range: The "range" is one of several ways of describing the precision of a series of measurements. The range is simply the difference between the lowest (or lower) and the highest (or higher) of the values reported. As the range becomes smaller, the precision becomes better.
Example: Find the range of 10.06, 10.38, 10.08, and 10.12.
Range = 10.38 – 10.06 = 0.32
4. Mean: The "mean" or "average" is the numerical value obtained by dividing the sum of a set of repeated measurements by the # of individual results in the set.
Example: Find the mean of 10.06, 10.38, 10.08, 10.12
(Note that the value 10.38, which is far greater than the other values, has a large influence on the mean, which is larger than three out of the 4 individual values.)
5. Median: The "median" of a set is that value about which all others are equally distributed, half being numerically greater and half being numerically smaller. If the set has an odd number of measurements, selection of the median may be made directly. (Example: the median of 7.9, 8.6, 7.7, 8.0 and 7.8 is 7.9, the "middle" of the five). For an even number, the average of the central pair is taken as the median (Example: the median of 10.06, 10.38, 10.08, and 10.12 is 10.10--the average of the middle pair of 10.08 and 10.12). Notice in the example that the median is not influenced much by the value 10.38, which differs greatly from the other three values. For this reason, the median is usually better to use in reporting results than the mean for small data sets.
6. Error: The absolute error of an experimental value is the difference between it and the true value. For example if the experimental value is 30.9 and the true value is 26.5, the error would be 30.9–26.5 or 4.4.
7. Relative percent error would be the error divided by the true value times 100: (4.4/26.5)x100%=16.6% or 17%.
Note: In CHM 235L you should use at least 3 significant figures to avoid rounding errors.