VANIER COLLEGE
CHEMISTRY DEPARTMENT
LABORATORY SAFETY REGULATIONS
1.
Do not enter the laboratory unless the teacher is present. Inform the teacher if you have to leave the lab area.
2.
Safety glasses and buttoned lab coats must be worn at all times while in the laboratory. Long pants and closed
stable shoes are recommended. Long hair must be tied back, and loose or hanging jewellery must be removed
before experiments are carried out.
3.
Eating and drinking is forbidden in the laboratory. Do not taste, touch or smell chemicals.
4.
Running, shouting or any other form of boisterous behaviour is strictly forbidden.
5.
Coats and backpacks must be kept away from the working area, and from the floor space between the benches.
6.
Only authorized experiments may be performed.
7.
Know the location of fire extinguishers, the fire blanket, the safety shower, the eyewash fountain and the firstaid kit in the laboratory.
8.
Read the labels of chemicals very carefully. Be careful in handling and mixing chemicals. You should be
familiar with the system of codes used to indicate safety hazards.
9.
All accidents, regardless of how minor they may seem, must be reported immediately to your instructor.
10.
If a chemical spills onto your skin or clothing, wash it off immediately with plenty of cold water and notify the
teacher.
11.
If a chemical gets into your eyes or on your face, wash immediately in the eyewash fountain with plenty of
water. Notify your instructor.
12.
If a chemical spills onto the bench or the floor, notify the teacher immediately and take appropriate action to
clean it up.
13.
Make sure that apparatus is stable and securely fastened. Never leave an “experiment in progress” unattended.
Turn off all equipment when it is not in use.
14.
Never aim the opening of test tubes or flasks at yourself or anyone else.
15.
Use fume hoods, as instructed, whenever toxic or irritating fumes may be evolved.
16.
Never place flammable material near an open flame or hot plate.
17.
Never use mouth suction for filling pipettes. Use a suction bulb.
18.
When diluting acid with water, always add the acid to the water.
19.
Do not force glass tubing or thermometers into rubber stoppers. Use water or grease to lubricate the tubing and
keep your hands close together during insertion.
20.
Never return unused chemicals to the stock bottles.
21.
The disposal of chemicals must be carried out in accordance with instructions given in the lab manual or by the
instructor.
22.
At the end of the experiment, wipe your bench space clean with damp paper towel.
23.
Wash your hands thoroughly before leaving the laboratory.
24.
The removal of chemicals or equipment from the laboratory is strictly forbidden.
Revised H’08
Laboratory Notes
PRECISION OF GLASSWARE
Graduated beakers are used to measure volumes roughly: they are containers, with a precision of
± 5%.
Graduated cylinders are used to measure volumes approximately: they are usually calibrated to
contain volumes with the following precisions:
10 mL: ± 0.1 mL,
25 mL:
± 0.1 mL,
50 mL: ± 0.2 mL,
100 mL:
± 0.2 mL.
Pipettes and burettes are used to determine volumes accurately: they are calibrated to deliver
certain volumes, and have a precision of:
1 mL pipette:
± 0.01 mL
20 mL pipette:
± 0.03 mL
5 mL pipette:
± 0.01 mL
25 mL pipette:
± 0.03 mL
10 mL pipette:
± 0.02 mL
50 mL burette:
± 0.02 mL
A volumetric flask contains an accurately known volume of solution at a given temperature
(often 20°C): it has a precision of:
100 mL volumetric flask:
± 0.2 mL
250 mL volumetric flask:
± 0.1 mL
USE OF QUANTITATIVE GLASSWARE
A. Volumetric flask
1. Clean the flask:
a) Use cold tap water: a volumetric flask should never be heated because
expansion alters the volume.
b) Rinse with two or three small quantities (about 10 mL) of distilled water. It
is not necessary to dry it.
2. Dissolve the solute in solvent in a beaker with a volume capacity less than that of the
flask. The beaker must be clean, but not necessarily dry. If it is necessary to heat the
solvent to aid dissolution, cool the solution before putting it in the flask.
3. Transfer the cool solution quantitatively to the volumetric flask in the following way:
use a funnel for the main bulk of the solution; wash out the beaker and transfer the
washing to the flask. Using a squeeze bottle wash the neck of the flask, the stirring
rod and funnel, allowing the water to go into the flask. This ensures the quantitative
transfer of all solute to the flask.
4. Fill up the flask to just below the mark. Stopper it and invert it quickly a few times.
Remove the stopper, wait 30 seconds, and add water dropwise to bring the bottom of
the meniscus to the mark. Invert again.
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5. Transfer a portion of the solution to a clean beaker in order to use it. To make sure
that the concentration is not changed by this procedure, rinse the clean beaker twice
with small quantities (3 mL portions) of the solution.
6. Clean the flask after use.
B. Pipette
A pipette is designed to deliver a certain volume of liquid at a given temperature.
(Precision: 10.00 ± 0.02 mL, for example).
1. Clean the pipette:
a) with cold tap water.
b) with small quantities of distilled water 2 or 3 times. This small quantity
should fill no more than the lower 10 cm of the pipette. (DO NOT FILL UP
THE PIPETTE FOR RINSING).
2. Put the reagent solution in a clean beaker, which has been previously rinsed with the
solution.
3. Rinse the pipette, 2 or 3 times, using small quantities of reagent solution.
4. Press (DO NOT INSERT) a deflated bulb to the end of the stem.
5. Fill the pipette about an inch above the calibration mark.
6. Remove the bulb and cover the stem with a dry finger.
7. Allow air to seep into the pipette until the bottom of the meniscus is level with the
calibration mark.
8. Remove the hanging drop by touching a glass surface gently.
9. Allow the contents to run into the reaction vessel. Hold the pipette vertical for 15
seconds after emptying.
10. Complete the delivery by touching the pipette tip to the liquid surface.
11. A small amount of liquid remains in the pipette and should not be blown or shaken
out. The pipette is calibrated to deliver the printed volume while retaining the last
little bit.
12. Wipe the outside of the pipette dry before pipetting the next sample.
13. Clean the pipette after use.
C. Burette
A burette is designed to deliver a variable volume of reagent and is calibrated in mL at a
given temperature.
1. Clean the burette with:
a) cold tap water
b) small quantities of distilled water.
2. Rinse the burette 2 or 3 times with small quantities of the reagent solution. Run the
reagent back and forth along the burette. Also rinse out the jet.
3. Close the tap and use a beaker to fill the burette.
4. Open the stopcock (tap) quickly, to fill the jet and get rid of air bubbles. Read the
level at the bottom of the meniscus to 0.01 mL, after 10 seconds. It is not necessary
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to fill the burette exactly to the zero mark.
5. Titrate (see below).
6. Clean the burette after use.
D. Titration Technique
The solution to be titrated should be pipetted into a beaker, or
preferably, an Erlenmeyer (conical) flask. The latter reduces the
risk of loss by splashing. If any solution does splash on the sides,
wash it back into the solution with a wash bottle, since this does
not change the amount of reagents present in the flask. When
titrating, operate the stopcock with one hand while the other hand
is free for swirling the flask.
The first titration is often “rough” in that the “end-point” may be
passed. The “end-point” is the first permanent color change of the
indicator. The first rough titration is used as a guide to the
approximate volume required. During the second and third
titrations, the solution can be run in rapidly from the burette to
within 1 mL of this approximate volume. Thereafter, add the
solution dropwise. Touch the flask gently to the tip of the burette to
remove a hanging drop, and wash it into the solution. The last two
titrations should be within 0.10 mL of each other.
USE OF THE ORION RESEARCH pH METER
General:
1. Proper electrode care is essential for obtaining reliable measurements.
2. To eliminate warm-up time, always have the meter in the STDBY mode. If the meter has
been disconnected, allow a half-hour warm-up period before use.
3. Stir both buffer and sample solution thoroughly while a measurement is being made.
4. Rinse electrodes with distilled water between measurements and blot.
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Standardization and use:
1. Turn the function switch to pH. With the electrode placed in buffer of pH 7.00, turn the
CALIBration control until the buffer pH is displayed.
2. Remove the electrode from the buffer, rinse and blot.
3. Place the electrode in the second buffer of pH 4.00.
4. Turn the black SLOPE control knob until the pH value of the buffer is displayed. If there is
a clear plastic temperature indicator, set it at the temperature of the buffer.
5. Remove the electrode, rinse and blot.
6. Place the electrode in the unknown sample. Swirl to equilibrate.
7. Allow the unknown and buffer readings to stabilize for about one minute. Read the pH
measurement directly from the display.
8. Leave the rinsed electrode immersed in the storage solution when you have finished.
USE OF THE ORION RESEARCH METER AS A VOLT METER
1. With the function switch in the STDBY mode connect the two electrodes to the volt meter.
The anode is connected to the “reference” connection at the back of the meter.
2. Turn the function switch to MV mode and measure the voltage (millivolts).
3. If the voltage reading is negative, reverse the polarity.
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USE OF THE SPECTRONIC 20D+ COLORIMETER
NOTE: The instrument will be used to display % Transmittance or Absorbance. The Mode
selection button is used to change what is displayed by the Digital readout (as shown by the
Mode indicator LED).
1. Instrument startup. Turn on the SPECTRONIC 20D+ using the power switch and allow five
minutes for it to warm up. Turn the wavelength control to the desired valued. Set the filter
to the lever to the proper position.
2. Setting the 0% Transmittance. Use the Mode selection button to change to % transmittance
if necessary. Set the instrument display to 0% transmittance by carefully rotating the power
switch/zero % T control knob with no sample tube in the sample holder. (There is an
automatic shutter in the light beam when no sample tube is in the instrument).
3. Setting the 100% Transmittance. Insert a clean sample tube containing only distilled water
into the sample holder. The outside of the tube should be clean and dry, and the white
vertical mark which has been etched on the tube should be aligned with the mark on the front
of the sample inlet. Close the sample inlet cover and rotate the light control knob (100% T)
until the meter reads 100% transmittance. This is to ensure that the instrument will measure
only the absorption due to the dissolved compound, not that of the sample tube and water as
well. Remove the sample tube.
4. Measuring the Absorbance. Use the Mode selection button to change to Absorbance. Insert
the tube containing the colored sample, close the sample inlet cover and read the absorbance
directly. The photometric accuracy is ± 2% T.
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