• Know the safety information from the introduction of your
• Pay attention, ask more questions if not understood, don’t perform unattended and
unrequired experiments, bench-tops must be free of backpacks, stools, etc.
• Protective clothing: Safety goggles, Footwear, lab coats
• Long hair tied up.
• Food & Drink prohibited.
• First aid:
• For acid, alkali or other chemical splashed on skin, cuts, abrasions or
• Chemicals on skin: Wash immediately, health services if immediate
• Chemicals in eye: Emergency eye wash station, health services
• Cuts, abrasions & burns: Report to TA; for all as well General Cont’D
• Fire & Explosions
• Stop, drop, roll
• Locate nearest exit
• Fire extinguishers
• Class A fires: ordinary combustible materials (paper, wood, plastics)
• Class B fires: flammable/combustible liquids (gasoline, grease, oil, solvents)
• Class C fires: electrical equipment (appliances, circuit breakers, outlets)
• To operate fire extinguisher (PASS)
• Pull the pin or locking device.
• Aim low, at the base of the fire.
• Squeeze the handle.
• Sweep slowly and evenly across the base of the fire.
• Safety with chemicals and glassware
• MSDS sheets, proper disposal, labelling, mercury spills, rubber bulb, stoppers, etc General Cont’D
• Review Appendix C: Laboratory techniques for all
techniques used this term.
• Qualitative Techniques
• Handle with attitudes of cleanliness, neatness, orderliness and respect
for the equipment.
• Gross Errors of Technique
• Caused by not paying attention.
• Some are due to:
• Spilling a solution of a sample – collision
• Splashing sample solution our of the container – addition of water
• Recording weight incorrectly.
• Neglecting to cover a beaker or flask & allowing impurities to fall into the
sample. Reading the start volume of burette’s.
• Neglecting labelling/identify – confusing containers.
• Weighing an object diff. temp than the analytical balance. General Cont’D
• Measurement of Mass
• Mass: measure of the quanitity of matter.
• Analytical balance: measures mass by comparing mass of an object
with the mass of a set of “weights” which have been universally
accepted for this purpose.
• Weight vs. Mass
• Weight: the force of the earth’s attraction on an object.
• Weight = mass x acceleration of gravity.
• Accuracy & Precision
• The “true” values. – But not always obtainable.
• Precision: A measure of the reproducibility of an experiment & can be
quantitatively expressed as an average or standard deviation.
• It’s not necessarily a precise measurement as many errors in the measuring
techniques can constant. General Cont’D
• Weighing Replicate Samples of a Solid
• Initial weighting:
• A measure of the clean, dry beaker/flask/etc = weighing beaker
• Analytical by difference:
• Take weighing beaker & 3 other flasks.
• Use paper to lift beakers.
• While weighing to desired weight, pour/tap a little bit into each of the flask so
that they all have the equal amount.
• The advantage of weighing the weighing beaker rather than the revieving
• A) Only n+1 weighings are required to prepare n samples: ie. 4 weighings
for 3 samples.
• B) The titrating flasks need not be dry, only the weighing beaker.
• It don’t matter if exactly the same amount is weighed into each flask. General Cont’D
• Use of a Burette in a Standardization Titration
• A burette used for accurately measuring volumes of a solution. The key
operations in using a burette are:
• A) Reading the meniscus level
• Proper rinsing
• Proper filling without spillage
• Removing air from the tip
• Touching off droplets from the tip
• Rinsing the burette
• Not dirty, small funnel, rinse around 3 times.
• Filling the burette
• Use small funnel to fill to near the zero with desired solution. Wipe.
• Initial reading of the burette
• Pour above 0, pour out from bottom until the meniscus reaches 0. General Cont’D
Continued: Use of A Burette In a Standardization Titration
• 2/3 cm into the titration flask. Rate of drops decreases.