APPENDIX L
ATU CHEMISTRY TEACHING ASSISTANT HANDBOK
BEFORE THE LAB
1. You should arrive before the start of the lab period to unlock student drawers, set out chemicals and special equipment (if necessary), and make sure everything needed is on hand. Unless unanticipated shortages require your preparation of additional chemicals, YOU ARE EXPECTED TO ATTEND THE INSTRUCTOR'S BRIEFING. There is a folder containing copies of the experiments on the desk in the stockroom. Taking time to read about the current experiment is advisable. Similarly users' manuals for special instruments (spectrophotometers, pH meters, melting point apparatus, etc.) are also available for your use. See the Lab Supervisor for these.
HELPING STUDENTS
2. The most effective teaching assistants are continually circulating around the lab, offering suggestions, answering questions, demonstrating proper laboratory techniques, and in general, being helpful. You should thus seek to maximize contact with students and watch regularly for opportunities to give help. A good TA will offer help but will not do the work for the students. Lounging about the stockroom or corridor, socializing with other TAs, or studying for your classes is unacceptable.
DRESS
3. Shorts and sandals are not acceptable. You are to provide an example for the students to follow.
BEFORE YOU LEAVE
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Lab lockers locked? |
Balances turned off? |
Balance area clean? |
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Fume hoods turned off? |
Lab benches cleaned off? |
Waste jars need attention? |
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Lights turned off? |
Stockroom doors closed? |
Lights turned off? |
Be sure and report any problems encountered in the lab (with reagents, equipment, or mechanical difficulties) to the Lab Supervisor.
OTHER DUTIES
5. Sometimes "dry labs" or "drills" will be performed in which your services may or may not be required. Check with the instructor. Likewise sometimes all students will finish experiment early--perhaps with an hour or so remaining in the 3 hour lab period . In both cases, check with the instructor or Lab Supervisor before leaving to see if there are other tasks for you to complete. Occasionally you may be asked to clean glassware, test safety related equipment, neutralize or destroy chemical waste, help with inventory, etc.
ABSENCES
6. If you must miss your scheduled work hours due to illness or unexpected problems, contact the instructor or Lab Supervisor before hand, or arrange for another qualified teaching assistant to cover for you.
SAFETY
7. One of your most important responsibilities is to make sure that students follow the following safety rules:
A. Eye protection is required at all times in the laboratory and where chemicals are stored and handled
Be sure that the splash goggles worn by any student have all of the covered vents in place on the goggles. If any of the vent covers are missing, have the student change goggles.
B. Horseplay, pranks, or other acts of mischief are dangerous and are prohibited.
C. The hazards of chemicals used should be known (e.g., corrosiveness, flammability, reactivity, stability, and toxicity). If the hazards are not known to you, it is your responsibility to find out the hazards. This can be determined from the MSDS sheets found in the Lab Supervisor's office, the lab book, or other references.
D. Eating, drinking, and smoking are not allowed
F. Appropriate clothing must be worn, a protective apron or lab coat is encouraged. Long hair is to be tied back. Long, loose sleeves should be rolled up. OPEN-TOED SHOES OR SANDALS ARE NOT PERMITTED. Neckties are especially discouraged.
G Mouth suction must never be used to fill pipettes, to start siphons, or for any other purpose.
H. Never perform experimental work when alone in the laboratory. TA's doing experimental work, or aiding student(s) in makeup work, should be sure that one of the chemistry professors or the Lab Supervisor is in the department, and that they know that the TA is working in the lab.
I. Always wash with soap and water before leaving the laboratory.
J. No chemicals or equipment may be removed from the laboratory without the specific permission and supervision of the instructor.
K. Read the labels carefully!
2. If an accident or safety-related incident occurs take appropriate first aid measures. If they have not been present, notify the Chemistry Lab Supervisor and the instructor and assist in the preparation of an Accident Report Form.
3. Familiarize yourself with first aid procedures and with the location of safety related equipment: eye wash stations, emergency shower, neutralizing solution, first aid kits, fire extinguisher, fire blanket, respirators, etc.
4. The books Safety in Working with Chemicals, Safety in Academic Chemistry Laboratories, and others are available for you to borrow. Similarly a Rapid Guide to Hazardous Chemicals in the Workplace and a file of Material Safety and Data Sheets on chemicals we use are available for reference if you have questions about individual chemicals.
5. Generally speaking, the hazards in the organic chemistry lab will be more pervasive and less immediately identifiable than in the general chemistry (mostly inorganic) laboratories. Consult the organic chemistry instructor or the above references as to the precautions needed when handling any unfamiliar organic compounds. At the risk of providing too short a list -- obviously if something is not listed here DON'T assume it's safe! -- the following chemicals (ones you could encounter in the lab) are potentially very hazardous to you and the students you are helping:
*concentrated acids and bases
*sodium and other alkali metals
*strong oxidizing and reducing agents
*heavy metals and their compounds (in rough order of decreasing toxicity: mercury, cadmium, lead, chromium, nickel, manganese, cobalt, barium, etc.)
*halogens (iodine, bromine in particular)
*thioacetamide and hydrogen sulfide
*acid anhydrides
*acid chlorides
*"-halo-carbonyl compounds
*benzene
*phenol
*carbon disulfide
*formaldehyde
*cyanides and nitrites
*organic peroxides and peroxide formers
6. Keep in mind that almost all of the organic reagents are flammable. The volatile ethers and hydrocarbons pose the greatest risks. When these types of reagents are in use, be especially watchful for situations that could lead to a fire or explosion.
7. You should be familiar with the general classes of incompatible chemicals, i.e., chemicals that can react with each other (a) explosively (b) in exothermic fashion (c) to produce flammable or toxic products. You should be especially cognizant of these possible combinations when advising students to discard their wastes in the common waste receptacles.
The table below gives a rough idea; specific listings of chemical incompatibilities are posted in the stockroom and around the labs.
ACIDS & BASES, METALS &
OXIDIZING AGENTS REDUCING AGENTS
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chlorates |
ammonia |
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chromates |
carbon |
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chromium trioxide |
metals |
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dichromates |
metal hydrides |
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halogens |
nitrites |
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halogenating agents |
organic compounds |
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hydrogen peroxide |
phosphorus |
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nitric acid |
silicon |
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nitrates |
sulfur |
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perchlorates |
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peroxides |
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permanganates |
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persulfates |
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These examples of oxidizing and reducing agents are illustrative of common laboratory chemicals; they are not intended to be exhaustive.
Be especially cognizant of theses possiblities when advising students to discard their wastes in the waste jars.
8. The colorful, large "Laboratory Safety" poster has been placed in the general chemistry lab, room 23. Study it and encourage the students to also study it.
INORGANIC SUPPLIES ORGANIZATION
1. For courses in the General Chem Lab, room 23, much of what the students need is in their drawer. They will be given an itemized list of everything that is to in their drawer. There are minimal extra pieces of glassware in the blue pans on the south wall of the lab. Emphasis is to be placed on returning only CLEAN glassware to the pans. The plastic dispenser bottles the lab contain soap solution. They should be checked before every lab session and refilled when necessary.
2. The stockroom has been organized to group items made of glass, metal, porcelain and plastic together. Please take some time to look around and note the location of items. Whenever you are returning items to the shelf, take the time to place the items in the correct location.
3. The solutions room, or "wet" room (room 23B) has had a few minor changes. Please take a few minutes to note the locations of items in this area. Be sure that any bottle that you return to the shelf in this room has a label that indicates the NAME, CONCENTRATION AND PREPARATION DATE for the solution contained. Don't label solutions for a particular course or experiment; that is, don't label as "1114, EXP #5" or "UNKNOWN Na ION for 2124 EXP 34."
4. When returning bottles to the wet room after a laboratory experiment, combine multiple bottles of similar solutions to conserve shelf space. Match the size of the storage bottle to the volume of the solution to be stored. Do not store solutions in flasks.
ORGANIC SUPPLIES ORGANIZATION
Consult the organic chemistry instructor or the ORGANIC LAB INDEX for help in locating specialized items. The organic chemicals are stored (by group) in the Organic Chemicals Stockroom. Consult the alphabetical organic chemical index for the location of a particular substance. Located to the right of the back door of the lab, next to the shelves are the switches for the ventilation fan and lights for the organic stockroom. The light switch is to remain on in the stockroom. In the summer or during hot weather, the air conditioner is left on 24 hours. During the late spring and/or fall, the ventilation fan is left on and the AC is turned off. Check with the Organic Chemistry Instructor or the Chemistry Lab Supervisor if you have any questions about this.
EMERGENCY PROCEDURES
In the event of a laboratory fire or toxic/flammable chemical spill your prompt action may be required.
Your main duties are to:
A) Make sure people in the immediate vicinity of the fire/spill are alerted as to the danger.
B) Alert the instructor and/or the Lab Supervisor on the scene. If these individuals are not immediately available you may need to,
(1) Attempt to smother the fire (w/ watchglass, sand, by closing a vent hood, etc.) or extinguish it with fire extinguisher. (You will be given training in the proper use of a fire extinguisher in a TA workshop that will be arranged.)
(2) Close doors to keep the fire from spreading. It is expected that the instructor or Lab Supervisor will contact the local fire department if necessary and co-ordinate any decision to evacuate the building; however, if for some reason they are not present, you should respond according to the seriousness of the situation and then make a complete report to them as soon as possible.
C) UNDER NO CIRCUMSTANCE SHOULD YOU ATTEMPT A RESCUE OR FIGHTING A MAJOR FIRE! You have not had the proper training and do not have the proper equipment to make such an attempt. Any rescues or firefighting will be carried out by the fire department or other properly trained and equipped individuals.
You are to be aware of the following:
1) the possible need to direct affected students to the emergency shower
2) the locations of fire blankets and fire extinguishers
3) the availability of organic vapor/acid gas respirators (There is one stored in the Waste Treatment Lab, room #23A and one in the organic lab.)
If the specific toxic or hazardous chemical involved in a spill or fire is known, and an instructor is unavailable to immediately take charge of the situation, consult the orange D.O.T. Hazardous Materials Emergency Response Guidebook located in the Lab Supervisor's office. Finding the chemical in the (white pages) alphabetical listing will direct you to a specific Guide number within the book. There, both potential hazards and emergency actions are listed.
Finally, other emergencies (plumbing, electrical, etc.) may require summoning the appropriate ATU physical plant (or other) personnel. The lab instructor, or the TA, should notify the Lab Supervisor if possible, or the physical plant (0261) if the Lab Supervisor is not available.
CLEANING GLASSWARE
If your duties include "dishwashing," note the following guidelines:
1. Wear goggles and vinyl gloves when washing dishes by hand.
2. Dispose of any chemicals remaining in glassware per the SPILLS/WASTE DISPOSAL section. If you don't know what something is make inquires as to its origin. (Be especially careful not to mistake concentrated acids or bases for water!)
3. Remove all labels as part of washing (soak in Alconox over night if troublesome).
4. If soap and water fails to adequately clean some glassware, consider the following steps:
a. letting it soak overnight in hot water
b. using a little acetone if organic chemical residues are causing problems
c. using a little 6 M nitric acid to help remove small troublesome deposits
d. in special cases, some may wish to employ specially formulated concentrated glassware cleaners - check with the Chem Lab Supervisor before doing this. Some of these containing Chromic acid are both highly corrosive and suspected of causing cancer. Use NO_CHROM-X where feasible.
5. If you don't know where to put clean, dry glassware, leave it in the dish drainer until you find out. (Don't guess as to where it might go!)
6. Be gentle in handling glassware - scratches and jolts can lead to breakage.
7. In using the dishwasher (Quant lab) observe the following
guidelines:
a. Use only at times when classes are not meeting in the adjacent classrooms (since its noisy!)
b. Don't put small items (that can fall through to the bottom) like spatulas, glass stoppers, corks, etc. in the dishwasher, similarly, make sure test tubes are secured in test tube baskets.
c. Be sure that you use only dishwasher detergent!!
8. To clean pipettes, place the pipettes with the tip up in a basket. Place one or two Alconox tablet in the bottom of the washer. Insert the basket with the pipettes into the washer, being sure that the basket handle is not in the path of the water inlet. Connect the inlet hose line to the faucet and turn the water on to flow at approximately 2 liters/min. (NOTE: BE SURE TO PLACE THE WASHER ON TWO BLOCKS OF WOOD IN THE SINK TO PRVENT BLOCKING OF THE DRAIN!) Allow the water to run for approximately 1 hour. To wash 25mL or 50mL pipette, since they are too long to be completely immersed in the regular pipette washer, the must be washed in the tall washer using the larger basket. Place the pipettes in the basket as described above; place two tablets in the washer; insert the basket into the washer; connect the rubber tube to the faucet and then insert the glass rod in the washer, but outside of the basket. Place the washer on wood blocks and then turn the water on. The level of the water in the washer during the washing process needs to be above the tips of the pipettes being washed.
PREPARATION OF LABORATORY EXPERIMENTS
If your job is to prepare the solutions or set out the chemicals for a particular lab please follow these guidelines:
1. Don't wait until the last minute to prep the lab - it may take longer than you think.
2. Notify the instructor and/or the Lab Supervisor if anything needed for the lab is unavailable and check with them on substitutions. List anything we are out of on the "order" sheet in the chemistry stockroom.
3. Refer to the "prep notes" for each experiment that the Lab Supervisor will have available for each lab and/or the Handbook of Chemistry and Physics for specific directions for the preparation of laboratory reagents.
4. Check the shelves of the wet room for the solutions that you need before mixing any solution. Consider the age of the solution and the stability of the solution before relying on an old solution.
If you find solutions that are out dated on the shelves of the wet room, place them with the waste to be disposed. Don't leave them on the shelf.
When preparing new solutions, especially large acid dilutions or NaOH, you should wear an apron or lab coat, gloves and a face shield.
5. Label all solutions, dry chemicals, or unknowns you set out, using water-proof ink. For solutions you make up from scratch be sure your label contains the following information:
*chemical name
*chemical formula
*date
*concentration, and if possible the precision with which concentration is known (i.e., .100 M implies 3 significant figures, .1 M implies 1 significant figure).
DO NOT use a pen with water soluble ink to write a bottle label! Test all labels to be certain they will not smear when the bottle is handled.
Be sure and remove old labels from bottles before adding new ones.
There are printed labels available, which are preferred, especially for the freshman labs where students may not be as familiar with chemical formulas as they should be. If these are used, it is recommended that the formula also be written on the label so that students can associate the formula with the name.
6. Set out concentrated acids and bases in several small bottles (put on acid trays) rather than in large jugs. Don't Leave rubber droppers inserted in bottles of concentrated acids - the rubber will decompose. It is recommended that you place the common acids and other selected solutions in the molded ground glass bottles. Be sure to add a label indicating the concentration and date of solution preparation.
7. Put light sensitive reagents in dark (amber) bottles. There are molded amber ground glass bottles for silver nitrate solutions.
8. Use dropper bottles when drops or up to 1 ml of a liquid are required.
9. Do not store chemicals in volumetric flasks, wash bottles, or beakers.
10. DO NOT STORE STRONG BASES (NaOH, KOH, etc.) IN GROUND GLASS BOTTLES.
11. If several small bottles of a reagent have been prepared, when storing the solution, combine the several small bottles into one larger bottle to conserve space on the shelves. Only combine solutions that have been prepared together.
12. The carboys should be used when preparing solutions that are required by all labs (.1N HCl, .1N NaOH, etc.) or where it is known that very large quantities of reagent will be used. Don't use the carboys to prepare solutions with a short shelf life.
13. If a solution you make up is known to have a short shelf life or has to be prepared fresh daily, put a special label on it that indicates this. These solutions will usually be discarded rather than saved when the lab is complete.
14. When returning acids and bases to the SOLUTIONS ROOM OR "WET" ROOM please make sure all lids are secure and that all exterior surfaces have been thoroughly rinsed. Put the largest, highest concentration containers nearest the floor -- the concentration and size should decrease with height above the floor. Small bottles of standardized solutions are kept on the top self.
15. When you break the seal and open a standardized solution please note the date you opened it if you later return it to the shelf. (These will not normally be used for general chemistry labs but are available for advanced projects)
16. Test any questionable reagents before setting them out, i.e., hydrogen peroxide that is old or other reagents with short shelf lives.
17. Use disposable gloves when handling hazardous materials, prep inside the fume vent hood if hazard warrants.
18. Set out clearly labeled jars for student lab wastes as directed by the instructor or the Lab Supervisor.
19. When selecting unknowns from a list of possibilities, choose those relatively non-toxic (and inexpensive!) if there are no other considerations. This will minimize later disposal problems.
20. Solid unknowns left over from an experiment can be saved and used the following semester provided they are (a) clearly identified (b) covered with a lid.
21. ALWAYS ADD CONCENTRATED ACID TO WATER (or in general, the more concentrated solutions should be added to the less concentrated) NOT THE REVERSE.
22. Prepare dilute acids/bases from concentrated reagents in pyrex glassware, with caution.
23. Once chemicals have been removed from a stockroom storage bottle they should never be returned to that bottle.
24. NEVER store potassium permanganate solutions in polyethylene bottles. Always transfer solutions from plastic dropper bottles to glass bottles for storage.
GRADING
If your job is to grade lab papers please follow these guidelines:
(1) Talk with the course instructor and establish what is important to him in grading the labs, max. number of points to assign, when you need to have the papers returned, etc. Continue to communicate and get feedback throughout the semester. If no specific guidelines are provided, consult the Chemistry Lab Supervisor.
(2) Generally speaking, part of the lab grade -- say 20% to 40% -- can be based on the accuracy with which experimental unknowns were determined. Keep in mind that recorded observations are just that; students are always told to record what they see, not what they are suppose to see. It is more important that a report contain inaccurate observations than not to contain any observations.
(3) Don't let students know you graded their papers. Questions about how a lab paper was graded should be directed to the Chemistry Lab Supervisor.
(4) All student lab grades are confidential and results are to be shared only with ATU faculty -- not other students.
(5) Weekly, or not less than biweekly, record your grades on the computer grade book in the Lab Supervisor's office. You will be shown how to access the proper file. It is important that this computer file be kept up to date. It would be a good idea to record the grades each time that you drop off a set of papers that have been graded.