Laboratory Reference Manual, Chemistry 201/202
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Safety & Lab Tips
Chem Safety Manual | Good Manners | Spills | Safe Techniques | Your Notebook

Everyday Lab Operations & Safety Tips

Lab operations involve a large assortment of operations. Many will seem strange and awkward at first, but weekly practice will soon make them familiar. That's the good news. The bad news, of course, is if you learn a procedure incorrectly (or incompletely) then repeated practice may build unsafe and dangerous habits.

The best way to correct a bad habit is to catch it before disaster strikes. Your instructors will be watching for bad lab habits and will talk to you about them as time permits. Unfortunately, it is simply not possible to watch any individual for more than a few minutes during a lab session. More help is needed and this is where you (and this appendix) come in. This appendix, and relevant sections of Padias (see especially p. 1-4 and p. 22-36), contain a number of tips for safe and efficient work. If you review this material from time to time, you will catch many of your own bad habits yourself and make your lab work safer and more successful.

Note: Students who routinely ignore instructions for safe lab work risk being dismissed from the lab.


Good Manners

Good manners make lab enjoyable and rewarding for everyone.

  • Clean up messes you make in communal work areas: reagent fume hood, balance room, etc. (wipe with wet sponge as needed)

  • At the end of each lab session

    • clean your work area (bench & fume hood) by wiping it with a wet sponge

    • dispose of all trash (unused chemicals, pipets, gloves, paper, broken glass) in the appropriate container

    • store all personal glassware in your desk whether it is clean or dirty, wet or dry

    • return communal materials (apparatus, reagents) to their appropriate storage areas (apparatus should be returned clean)

  • Do not use any unfamiliar equipment without the approval of your instructor or laboratory assistant

  • Notify your instructor or laboratory assistant immediately if

    • you become injured

    • you get splashed by chemicals

    • you notice/start a fire or explosion

    • you spill a substantial amount of material (or break a mercury-containing thermometer

  • Protect the integrity of communal reagents

    • Do not put anything into a reagent bottle except a clean pipette/spatula

    • Cap bottles as soon as possible

    • Return reagents to their original locations as soon as possible

  • Label and properly store all chemicals you make

    • Store volatile liquids in a fume hood in a tightly capped container

    • Do not cap a hot liquid until it has cooled to room temperature

    • Do not use wood/rubber corks, plastic caps, and parafilm to cap organic liquids (these caps may be suitable for solids and aqueous solutions)

    • Use Teflon stoppers and glass stoppers to cap organic liquids


Handling spills

Spills pose a danger to everyone in the lab (and especially to the custodians who clean the labs each evening). You must take responsibility for all of your spills. 'Responsibility' includes:

  • determining the type of spill
  • performing a chemically appropriate clean-up
  • keeping other people from entering the spill zone until you have completed the clean-up (especially important for broken glass and mercury; these travel far when broken or spilled)
  • notifying your instructor (especially important for hazardous substances, like spilled mercury)

The on-line Chemistry Safety Manual (section 3.3 - Dealing with Accidents) contains basic instructions for handling acid, base, and mercury spills. The Safety Manual (section 3.4 - Waste Disposal) and Padias p. 4 contain instructions for disposal of broken glass.

Organic compounds. Spilled organics present a special problem because these substances vary in volatility, odor, aqueous solubility, reactivity, flammability, and health impacts.

Solids can generally be swept up and discarded in the organic waste. (Traces of solid might be collected with a damp piece of paper and discarded, paper and all.)

Liquids are more challenging. If a small amount of a volatile liquid (say, a low boiling solvent) is spilled in the hood, no special action is necessary or possible; most of the liquid will evaporate before you can clean it up. Larger spills, and spills that occur outside a fume hood, should be treated with adsorbents (stored around the lab in "spill kits"). Consult the spill kit for instructions regarding how to apply the adsorbent to the spill, and how to clean up, label, and discard the used adsorbent.


General safety

Safe lab work requires attention to three potential ‘targets’: yourself, other people inside the lab, and the outside world. This page discusses each target and offers suggestions for performing specific lab operations more safely (see also Padias p. 1-3 for brief instructions).

Protecting the outside world. The most obvious step for protecting the outside world is to dispose of all materials properly (see Disposal). Another, less obvious step is avoid lab operations that pollute the environment.

Unfortunately, a total ban on lab pollution is hard to achieve. Volatile solvents, even when used in fume hoods, pollute the atmosphere. Compounds that go down the sink ultimately pollute streams and soil.

A perfectly non-polluting experiment may be impossible, but this does not make us less responsible for the outcome. If we cannot eliminate unsafe chemical emissions from the Chem 201/202 lab, we should at least try to minimize them. This principle has guided the selection and design of our experiments, but more needs to be done. You must also play your part and make sure that all chemicals within your control are disposed of properly.

Protecting yourself and other people inside the lab. There are three things you can do to keep yourself and others safe while working in the lab:

  • Set up barriers

    • Wear goggles at all times

    • Wear protective clothing and shoes at all times (no bare toes, no bare tummies, no bare shoulders, etc.)

    • Perform all operations in a fume hood and watch your material through the hood window

  • Keep your distance

    • Keep your face at least 2 feet from your materials and apparatus

    • Never hold an apparatus or compound over your face/head

    • Never point the opening in a flask or test tube at someone else

  • Avoid dangerous operations

'Avoid dangerous operations' is an extremely important principle, but how does it work? How do beginners, in particular, recognize a dangerous operation? The following list provides safety tips organized by the type of operation.

Measuring compounds

  • Measure solids on a balance

    • Put clean weighing paper (or weighing boat) on balance and press “Tare”

    • Add solids by spatula until the desired weight is approximated

    • Do not return contaminated compounds to reagent bottle

    • Clean up spills around the balance

  • Measure liquids by volume in a graduated cylinder in a fume hood

    • Solutions: Calculate #moles from liquid volume and solution concentration

    • Pure liquids: Calculate #moles from liquid volume, density, and molecular weight

  • Useful approximations

    • 20 drops from disposable pipet = 1 mL

    • 1 pipet load = 1 mL (assumes partially filled disposable pipet)

Transferring compounds

  • Perform all transfers (especially liquids) in a fume hood

  • Contaminated ground glass joints do not work properly. Keep them clean

    • Use a funnel to place compounds in a round bottom flask or separatory funnel

    • Use a wide-necked, short stem (powder) funnel for solids

  • Never (NEVER!) pipet liquids by mouth

Heating compounds

  • Organic compounds produce flammable vapors and can be ignited by sparks from an electronic heater or flame

    • Use a ceramic heater that matches or exceeds your flask size

    • Plug the heater into a voltage controller and never the wall outlet

    • Set the heater on top of a lab jack so it can be quickly removed in an emergency

    • Start off with the heater and container touching (otherwise the heater may become too hot)

  • Spark-producing heaters can be used to heat non-flammable compounds

    • Use a hot plate/stirrer to heat aqueous solutions

    • Use a heat gun to dry clean glassware, but never use a heat gun on flammable compounds or plastic (melts)

  • Never make an open flame in our lab

  • Never heat glassware to dryness (except to dry clean glassware with a heat gun)

    • If glassware becomes dry by accident, turn off heat and allow glassware to cool on its own (remove heater if practical)

  • Never heat a closed system (even partially evacuated closed systems)

  • Turn off heaters as soon as you are finished with them

Applying a vacuum

  • Unsafe evacuation procedures can lead to explosions (heating a partially evacuated closed system) or implosions (collapse of thin-walled or damaged glassware). Although they sound different, they look the same: dangerous glass shards and chemicals spray all over the lab

  • Use heavy-wall rubber tubing for vacuum filtration and vacuum distillation

    • Thin-wall rubber tubing and tygon (plastic) tubing tend to collapse leaving a partially evacuated closed system

  • Use heavy-wall unscratched glassware for vacuum filtration and vacuum distillation

    • Never evacuate an Erlenmeyer flask (thin glass walls makes flask liable to implode)

  • Water aspirators - set water flow to its maximum rate to create a strong vacuum

Water hoses

  • Use thin-wall rubber or Tygon (plastic) hoses

  • Turn off water when you do not need it (and before you leave the lab)

  • Condensers – use a steady trickle of water to keep a condenser cold

    • Use metal springs to lock hoses on condensers

    • Insert the drain hose at least a couple of inches into the sink to anchor it there

  • Aspirators – use the maximum water flow to make the strongest vacuum


  • Cleaning options

    • Traces of organic compounds – rinse with acetone (send liquid into organic waste container)

    • Otherwise – wash with brush, soap, and water; rinse with deionized water; hang on draining rack (make sure you put all of your glassware, wet or dry, in your desk at the end of each lab period)

    • Never dry glassware with compressed air. Compressed air pipes contain an ugly assortment of microscopic contaminants (water, oil, dust, etc.) that spew out in the air stream

  • Drying options (use these when an experiment calls for clean, dry glassware)

    • If glassware is already clean – dry glassware with heat gun starting from the bottom

    • If glassware is dirty – clean (see above), rinse with acetone, and then rinse again with a small amount of the dry solvent that will be used (send acetone and solvent rinses into organic waste container)

    • Never dry glassware with compressed air. Compressed air pipes contain an ugly assortment of microscopic contaminants (water, oil, dust, etc.) that spew out in the air stream

  • Fractionating column

    • Normally no cleaning is required (we use this apparatus for only one experiment and this use does not normally contaminate the column)

    • If cleaning is required, rinse with acetone (send rinses into organic waste container)

  • Separatory funnels

    • Do not dry a separatory funnel (normal usage involves pouring water into the funnel anyway)

    • Disassemble the funnel before storing it in your lab bench, otherwise the pieces may stick together

  • Assembly – disassembly of multi-piece apparatus

    • Assemble by clamping the bottom piece (usually a round bottom flask) to the monkey bars. Other pieces should rest on top of this one, and can be secured with additional clamps (either loose clamps to monkey bars or plastic clamps). Never dangle the lowest piece from the other apparatus

    • As a rule, do not place grease on ground glass joints. The grease tends to dissolve in your materials and contaminate them (exception: a light layer of silicone grease should be applied to glass stopcocks)

    • Do not grease Teflon surfaces

    • Disassemble all apparatus before storing it, otherwise the pieces may stick together


Your Notebook

Every experiment in your notebook is supposed to contain hazard information and handling instructions for the compounds that you will be working with. The question that vexes a beginner is how much hazard information, and which handling instructions, really need to be listed. Do we really need to write down:

Water - hazardous, do not inhale

One way to approach this problem is to recognize that there is a spectrum of lab hazards. Some are routine. Others are extreme. The routine hazards usually don't require special mention in your notebook, but the extreme hazards always do.

A routine hazard is one that is widely recognized. You don't have to tell a fireman that wood burns, but you might want to tell him that the bottle of liquid in the fume hood does. A routine hazard is also any hazard that is adequately managed by following the basic rules of our lab: wear goggles and perform all experiments in the fume hood. More on this idea later.

An extreme hazard is any hazard that might not be widely recognized, e.g., the flammable liquid in the bottle, the toxic gas in the gas cylinder, the metal that explodes on contact with water. It is also any and every type of hazard that demands more attention than "wear goggles, do all experiments in the fume hood." If our routine practices will not keep you safe, then you should list the hazard in your notebook and list appropriate handling/disposal instructions as well.

Let's make these distinctions between routine and extreme hazards a little more explicit by considering three particular types of chemical exposure: eye contact, inhalation, and skin contact.

An example of a routine eye contact hazard is a compound that accidentally gets squirted into your eye. Eye contact with foreign substances is always very bad. This explains our basic rule: wear safety goggles at all times. However, because eye contact is a routine and universal hazard, you do not need to list "eye contact hazard" next to every compound in your notebook.

On the other hand, there are exceptions that must be considered. A compound that is especially reactive towards eye tissue should be regarded as an extreme hazard and should be listed as such in your notebook. All compounds that are labeled as lachrymators belong in this category. Lachrymators irritate eye tissue to an extreme degree and mere vapors of a lachrymator can initiate eye irritation and damage. Notice that goggles, our routine method for preventing eye contact with foreign substances, do not control vapors well. The inadequacy of goggles in dealing with lachrymators is a perfect indication that lachrymators need to be listed as extreme hazards in your lab notebook.

Similar thoughts apply to inhalation hazards. Our routine assumption is that breathing large amounts of any organic vapor is bad for you. To provent this, we have you perform all experiments in a fume hood.

Does this mean you can skip listing "inhalation hazards" in your notebook? Not necessarily. Notice that "perform all experiments in a fume hood" does not eliminate the possibility of taking a compound outside the hood to weigh it, dispose of it, or store it. A compound that produces toxic (or odorous or explosive) vapors should never be taken outside the fume hood. Moreover, every person who enters the lab ought to be informed that you are working with a compound that produces dangerous vapors. These kinds of compounds are not adequately managed by our basic lab rule, so they should be regarded as extreme hazards and appropriate hazard information and handling instructions (which may include special procedures for measurement, storage, and disposal of the compound) must be entered in your lab notebook.

Skin exposure poses a different kind of problem. First, skin may tolerate more chemical exposure than eyes and lungs. This explains why we don't have a basic rule regarding gloves. By now you should realize what this means. If the routine procedure (no gloves) is inadequate for a given compound then the compound should be treated as an extreme hazard. It is your responsibility to decide when gloves are appropriate and what kind of gloves are appropriate (EHS and the Stockroom can provide you with information about the chemical properties of different types of gloves). You should make a special effort to identify corrosive and/or strongly reactive reagents (like aqueous base), or strongly penetrating agents (like DMSO), or potential allergens, that might present significant skin hazards and list this information along with suitable handling instructions in your notebook.

This discussion hardly exhausts the list of possible lab hazards. Here are some others that should be listed in your notebook: 1) extremely hot or cold objects (contact with these can damage your skin; hot objects can also initiate a chemical reaction, fire, etc.); 2) any procedure or compound that can react vigorously or explosively with other substances; 3) flammable compounds; 4) water-sensitive substances (compounds that react quickly and exothermically with water); 5) any procedure that yields a gaseous product (gas confinement builds pressure inside an apparatus and runs the risk of explosion; also, some gases, like hydrogen, may be chemically reactive).


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