On September 15, 2014, a high school chemistry teacher in Colorado intended to demonstrate the characteristic emission spectra of metal ions with a flame test large enough for the entire classroom to watch. The different colored flames produce the so-called rainbow effect, which would certainly impress the students.
Unfortunately, in this instance, four students were injured. All four
suffered burns, one seriously.
Traditionally, the “Rainbow Demonstration” is performed by
placing 5–7 grams of a metal chloride in a glass Petri dish and then
adding 7–10 milliliters (mL) of methanol. The lights are dimmed,
the mixture is ignited, and the audience observes the flame test
color. But demonstrators are cautioned not to add more methanol
to the Petri dish after starting the demonstration — the mistake
this teacher made.
The flame quickly traveled back up into the bottle and ignited
Understanding the hazards of chemicals
the rest of the alcohol. Pressure built up within the bottle, as
the temperature of the gases produced in this chemical reaction
quickly increased, and the bottle spewed a fiery stream of alcohol
at a distance of 12 feet ( 3. 6 meters), hitting a student in the chest.
In September and October 2014, a total of 22 students and two
adults were injured throughout the United States in four separate
incidents involving methanol used in rainbow demonstrations.
These accidents could have been prevented by using metha-
nol’s Safety Data Sheet (SDS). Formerly known as Material Safety
Data Sheets (MSDS), SDSs contain a wealth of information in a
simple, easy-to-read format. Each chemical has its own SDS, and
learning to read them can help you handle the chemical appropri-
ately and address any potential health hazards.
If you ever read the labels of chemical products, you may have
noticed a lot of symbols. The use of these symbols is a direct
result of recent efforts to modernize and standardize the way
chemicals’ potential hazards are labeled. One update is the
adoption of a uniform set of pictograms developed by the
United Nations, which is used throughout the world. (Take
the quiz on page 23 to see if you can match these symbols
with their warnings.)
An SDS meets the requirements of the Occupational Safety
Using an SDS
and Health Administration (OSHA), a U.S. federal agency created
to ensure a safe work environment for all employees. OSHA man-
dates that all workers exposed to chemicals have the right to know
about the potential hazards of these chemicals. Although OSHA
regulations were developed to protect employees, state laws typi-
cally extend similar protections to students. So when you or your
professor order chemicals, each chemical will come shipped with
an SDS, either in written or electronic form. Having an SDS on hand
for each chemical you use is not just a good idea — it’s the law.
The SDS for any particular chemical is written by the supplier
or manufacturer of that chemical. There is a great deal of moti-
vation for these companies to be thorough and accurate, as any
incomplete or false information could lead to serious harm by
the user, not to mention a lawsuit. (Note that an SDS does not
address the possible hazards that could occur as a chemical reac-
tion moves takes place, so it’s a good idea to look up SDSs for the
products and by-products of your reactions, too.).
An SDS can seem like a flurry of cautions and warnings. Learning how to sift through the information is the key to dealing
with dangers and using chemicals safely. Consider an example
of an SDS for methanol.
Section 2 of the SDS is labeled “Hazards Identification.” A typical
listing for methanol under this section may read as shown below.
Highlights from “Section 2:
• Highly flammable liquid and vapor
• Keep away from heat, sparks, open flames, hot surfaces —
• Toxic if swallowed, in contact with skin or if inhaled
• Causes damage to organs
• Use only non-sparking tools
• Take precautionary measures against static discharge
This section documents the highly flammable nature of
methanol, It is so flammable that there is a direct warning
to avoid open flames and even sparks.
Although the label says that both the liquid and vapor are
flammable, liquids themselves do not actually burn. When a
liquid is ignited, it is the vapors on top of the liquid that actually
burn. For a liquid to be considered flammable, it needs to evaporate so quickly that the vapors above the surface of the liquid
concentrated enough to combust. If enough heat is applied,
these vapors will ignite.
Even though most people know better than to pour a
flammable liquid, such as methanol, onto an open flame,
Safer Demos Through
Safety Data Sheets
BY BRIAN ROHRIG
THIS ARTICLE WAS ADAPTED WITH PERMISSION FROM “SAFETY
DATA SHEETS: INFORMATION THAT COULD SAVE YOUR LIFE.”
CHEMMATTERS. DECEMBER 2015/JANUARY 2016, P. 5–7.