Chemical Safety in the Laboratory
A chemistry laboratory, like engineering labs and construction sites, can have many materials
that can be dangerous if not handled properly. A basic appreciation for the hazards of the
materials handled in these situations is critical in staying safe.
Acids and Bases
Acids and bases are both corrosive to organic materials (including you) and often to other
materials such as metals. Their chemical action is not the same, but the hazards they pose are
often similar. Acids generate H3O+, hydronium ions, in water. Bases are most often identified as
releasing OH- to solution. More refined definitions for both types of compounds exist.
Acids and bases both see uses outside of the chemistry lab. Muriatic acid is the common name
for hydrochloric acid, which can be used for cleaning masonry. Lye, a name which has been
used as a common term for sodium hydroxide or potassium hydroxide, is a base that also has
many common uses, for example drain cleaning. Whenever handling these materials
concentrated care must be used to avoid injury. Protective gloves and eyewear are critical.
Often, more dilute solutions of acids and bases need to be made from concentrated solutions. An
important safety rule to observe is to always add acid to water rather than add water to acid. This
principle should in general be observed for any concentrated solution; add it to water rather than
the other way around. The mixing process often generates a great deal of heat, and can
potentially boil small amounts of the acid near the surface causing it to spit potentially causing
harm.
Metals
Metals can be surprisingly combustible. One does not usually think of aluminum or iron as
something you can light on fire, but some metals burn exceptionally well. Magnesium, for
instance, is used in all manner of flares. Aluminum is very difficult to light due to a thin layer of
aluminum oxide, a highly unreactive material, that forms on its surface. If this layer is removed,
aluminum burns exceptionally well. In fact, it can be very dangerous to cut aluminum with a
torch. Once lit, it is nearly impossible to put the fire out. The best options for metal fires, were
you to encounter one, are specialized fire extinguishers, or buckets of sand to douse the flame.
Oxidizing Agents
Oxidation is a common problem. It is the process why which steel beams on bridges and the
undercarriage of your car turn to rust. It is also in part the process by which your body ages.
Oxidation is a process in which electrons are removed from a particular element or compound
through a reaction with oxygen. This process is, fortunately, relatively slow in everyday
experience. Some chemicals are able to greatly accelerate these processes. Certain acids, known
as oxidizing acids, such as nitric acid HNO3 are oxidizing agents. Household bleach, sodium
hypochlorite, NaOCl, is also a strong oxidizing agent. These kinds of materials can cause severe
injury if they come in contact with skin or eyes.
Procedure
Chemicals and Organic Matter
Eggs are made mostly of protein. This is the same material that your skin, flesh, and eyes are
made of. Observe the reaction of eggs and several different chemicals to get a feel for the effects
of caustic materials on biological materials (like you). Sugar is also an organic material. It is a
chemical cousin of cellulose, which most plant material contains in great amount. It is also not
too dissimilar from many molecules that people are made of.
Materials:
Egg white
Small beakers or watch glasses
16 M nitric acid (HNO3)
bleach
6M sodium hydroxide (NaOH)
50 ml beaker
18 M sulfuric acid (H2SO4)
sugar (sucrose, C12H22O11)
glass stirring rod
Put a sample of egg whites in three separate containers. Add a few drops of nitric acid to one,
bleach to another, and sodium hydroxide to the third. Observe what happens to the egg over
time.
Do the following in a hood! Place 10g of sugar in a 50 ml beaker. Add 10 ml of sulfuric acid,
and stir thoroughly. Observe the color changing as you stir. Once thoroughly mixed, close the
hood sash and wait until something dramatic happens.
Chemical Spills
Chemical spills need to be cleaned up quickly and correctly to prevent potential exposure. A few
drops of acid on a table can easily later get on your hands and burn you. One inattentive scratch,
and your chemical contaminated hand could even get chemicals in your eyes. Often neutralizing
a spill before cleaning it up is an important step, especially for acid spills.
Materials:
6M hydrochloric acid
large beaker
sodium bicarbonate (NaHCO3)
In a hood, pour ~5 ml of hydrochloric acid in the bottom of your large beaker. This simulates a
spill. Add sodium bicarbonate and carefully mix. Note the vehement reaction. You must add
sodium bicarbonate until all of the acid has reacted. You may need to use a scoopula to mix the
contents to get the acid all to react. Once there is no more foaming, scrape al of the contents out
and into the proper waste container. If you were cleaning up a benchtop, you would have to
wipe up any residue left over with a wet towel and also put that in chemical waste.
Metals and Corrosion
As previously mentioned metals can be quite reactive. Observe the following reactions of
aluminum and magnesium.
Materials:
6M NaOH
beaker
aluminum foil
magnesium
Fold a piece of aluminum foil one or two inches on a side into a small bowl shape. Place it at the
bottom of a beaker. Pour 1-2 ml of NaOH into the middle. Observe the beaker until a reaction
occurs. It may take a little while to get going.
Do the following in a hood. Get a strip of magnesium a few inches long. Light a Bunsen burner.
Light the magnesium with the burner. Do not look directly at the flame.
Analysis
Describe the effects of various chemicals on eggs. Describe the effects of sulfuric acid on sugar.
What is likely to happen if you expose yourself to the same chemicals?
Describe your clean up procedure for the chemical spill. Why might it be important to neutralize
the acid before cleaning it up?
Describe the reaction of aluminum. What purpose might having aluminum in Drano serve?
Describe the reaction of magnesium.