Intro Lab Methods
Chapter 5
Basic Material Handling Techniques
In any laboratory, certain techniques are regularly performed and are essential to
most routine work. These techniques include the measurement and use of chemicals
and other hazardous substances and the operation of laboratory equipment. A
competent technician uses these basic techniques, confidently and without risk, in
routine work and with any new procedures.
Procedures include:
• material transfer
• weighing
• volume measurement
• solution preparation
• filtration
• heating, cooling and drying
• temperature measurement
• using gas cylinders
• particle size reduction
• cleaning and drying glassware.
Material transfer
Materials are routinely moved from one container to another during laboratory work.
The transfer usually has to meet at least one of the following requirements:
• safety with materials which are toxic, corrosive or dangerous in some way.
• quantitative transfer where any loss will affect the accuracy of the task.
• contamination control either from the surroundings to the material or vice versa.
Weighing
Weighing of materials is fundamental to most procedures. You should be competent
at working with each of the balances found in the general laboratory.
Weighing rules
• all balances must be clean, level and zeroed
• all chemicals must be weighed by difference in a container
• don’t weigh hot or wet objects
• clean up all spills immediately
• check the balance has returned to zero and reset it before you leave.
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Common terms used with weighing or the use of a balance include:
• clean: nothing on the balance pan
• level: the workbench and the balance need to be horizontal
• balance reading: the mass on display
• true mass: the mass of the sample after the container mass has been subtracted
• reset: leave the balance clean, level and zeroed
• weighing by difference: an empty container is weighed, the sample is added to it
and the mass of the container and material recorded, the difference between the
final mass and the empty container is the mass of the material
• taring: the balance pan is adjusted to read zero with the empty container sitting
on the balance pan, when the material to be weighed is added, the displayed
weight is the weight of the added material only
Volume measurement techniques
The are many skills involved with working safely with liquids. Your teacher will
demonstrate these skills and have you practice them.
Liquid transfer involves transfer of all the liquid. Commonly losses occur with
spillage, dribbles or failure to pour all of the liquid from one container to another. You
will practice transferring liquids in the laboratory.
The transfer of the correct volume also is dependent on having the correct volume to
transfer. Measuring liquid volume requires you to read the position of the meniscus
on a scale. The meniscus is the curvature or shape adopted by a liquid surface near
the walls of any container. All volume readings are taken by lining up the flattest
portion of the meniscus with the scale on the vessel. For water it is always the
bottom but other liquids eg mercury have convex meniscus.
Volume measurement may use quantitative or qualitative glassware.
Quantitative glassware is highly accurate and reliable and includes:
• pipettes
• burettes
• volumetric flasks
Qualitative glassware is not very accurate or reliable and includes:
• graduated beakers or flasks
• measuring cylinders
• droppers
• an experienced guess in unscaled glassware
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Pipetting techniques
• perform a sacrificial rinse with the fill solution
• overfill to above the mark
• set the bottom of the meniscus on the line
• allow to drain in a vertical position until no more liquid runs out
• touch the tip on the side of the receiver to draw the final amount of liquid out
• do not blow out, there must always be a little left behind, which is allowed for in
the original calibration
Burette techniques:
• perform sacrificial rinse with the fill solution
• overfill to above the mark
• open tap fully and ensure all air bubbles are driven out of the tap and the tip of
the burette
• set the bottom of the meniscus on the chosen mark - usually zero
• clamp in a vertical position at a convenient height above the receiver
• touch a wastes receiver onto the side of the burette tip to draw any excess liquid
off the tip
• check your mark and record its value
• run the required volume of liquid out and ensure any suspended drop on the
burette tip is also transferred
• read and record the new volume, perform any necessary subtractions
General volumetric flask rules
• perform a sacrificial rinse using the intended solvent
• add the solute first, quantitatively, without loss
• add some solvent to ensure the solute dissolves completely
• mix well by inversion and swirling
• solvent is added until the bottom of the meniscus is on the line, mix well and
support the weight correctly
• label with name, concentration, date and appropriate safety advice.
Pipettors
Also known as micropipettes, auto pipettes
These are hand held filling devices to measure, very accurately, a very small volume
of liquid or fluid.
The device is operated via a plunger to provide the suction (the plunger moves up or
out of the device) and delivery (the plunger moves down or into the device).
The fluid or liquid only enters a disposable plastic tip, which may be yellow, white,
green or blue. Different coloured tips have different capacities, but it is the pipettor
that measures the actual volume. If you don’t fit the correct size you may overfill the
tip and cause all sorts of problems. Generally the design of the device does NOT
allow you to fit the wrong size tip.
The device can be:
• a fixed volume device eg 50 or 100 or 200 μL (microlitres)
• a variable volume device across a wide range
• multiheaded eg 5 or 10 or 20 tips may be fitted
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Rules For Use
TO FILL
depress the plunger to the first stop, insert into your sample and
allow the plunger to return SLOWLY to its rest position.
TO EMPTY position tip over the receiver (as close as possible to the floor of
the receiver to avoid splashes) and depress the plunger
SLOWLY, past the first stop, all the way to the second stop. This
blows all of your sample out of the tip.
PROBLEMS accurate measurement and delivery is linked to an airtight seal.
If you rush, you can force air or contents to escape.
Do the operations slowly and smoothly.
Preparation of solutions (common terms)
Solute: the material which is being dissolved
Solvent: the material which does the dissolving
Solution: a solute dissolved in a solvent
Concentration: the ratio of the quantity of solute to the quantity of solution
Make up to volume: the required amount of solute is added to a container and
solvent is added until the required final total volume is reached
Dilution: making a weaker solution from a stronger one by addition of a solvent
Serial dilution: making a more dilute solution by accurate dilution of an original
solution and then repeating the procedure on the diluted solution to make even more
diluted solution(s) whose concentration are accurately known with respect to the
original solution.
Cleaning and drying of glassware
Laboratories have a huge variety of glassware and equipment, which needs to be
clean, before it can be used. Equipment must be clean before use to prevent crosscontamination which may affect the analysis results
Cleaning methods include the use of:
• solvents
• strong acids
• abrasives
• sanitising agents
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Practical work 5.1
Basic material handling techniques
All chemicals whether solid, liquid or gas must be handled with caution. This
practical looks at the techniques to be employed when transferring solids and liquids.
Practical work 5.2A
Introductory weighing task
The aim of the practical is to become familiar with the different types of balances
available in a general laboratory. Your instructor will demonstrate the correct
procedures to follow when using a balance.
Practical work 5.2B
Calibration of laboratory balances
Practical work 5.3A
Elementary volumetric measurements
The practical is designed to provide the skills necessary to make volume
measurements. It looks at the degree of accuracy of different measuring devices
such as a beaker and volumetric flask.
Practical work 5.3B
Quantitative volumetric techniques
Practical work 5.3C
Calibration of volumetric glassware
Practical work 5.4
Solution preparation
You are required to prepare and validate known concentration solutions.
Using an analytical balance weigh out accurately the mass of each solute indicated
in the result sheet table.
Quantitatively transfer the solid to a 100mL volumetric flask and make up to the mark
with distilled water
The teacher will show you the checks to be made on your sample and the previously
prepared sample.
Practical work 5.4B
Advanced work with solution preparations
A primary standard solution will be prepared followed by dilution to prepare a
secondary standard solution. If the solutions do not meet the necessary tolerances,
they will need to be remade.
Using an analytical balance accurately weigh out the mass of each solute listed in
the work sheet. (For hydrochloric acid, dilution by pipette is required).
Quantitatively transfer the solid to a 100mL volumetric flask and make up to the mark
Perform the dilutions and validity checks as indicated by the work sheet.
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Practical work 5.5A
Simple filtration
Note: The chemicals in this practical are very toxic. Ensure that any spills are
reported and also ensure that hands are properly washed if skin contact occurs and
before leaving the laboratory.
1. Record the identity and quantity of each of the chemicals
2. Dispense an aliquot for each reagent bottle into a clean dry beaker
3. Carefully mix, using a glass stirring rod, the beaker contents over a steam bath
for five minutes
4. Cool the beaker in an ice bath
5. Set up a filtration apparatus as shown by your teacher and using a labelled, preweighed filter paper filter your sample.
6. Wash the filter cake well with distilled water
7. Transfer the filter cake and filter paper to a labelled watch-glass and allow to dry
8. Reweigh and determine the amount of solid material.
Practical work 5.5B
Separation by filtration and centrifugation
Practical work 5.6
Heating and temperature measuring equipment
Practical work 5.7A
Temperature calibration
Practical work 5.7B
Other laboratory temperature sensors
Practical work 5.9
Manual methods of particle size reduction
Practical work 5.10
Glass cleaning
You will be given an amount of dirty glassware and equipment and a demonstration
of various cleaning techniques. You will then practise the methods on your items.
The teacher will inspect your efforts and may require you to attempt other methods
or repeat the current process.
Practical work 5
Application of heating equipment
This practical looks at the workings of various types of heating equipment which are
commonly in use in a general laboratory. (Bunsen burner, Meker burner, hotplate,
steam-bath, etc)
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Student Name:
Practical:
Weighing skills
Practical Number: 5.2A
Date Performed:
Date Submitted:
Text book References
Procedure:
Use the range of laboratory balances supplied as shown during your teacher’s
demonstrations. You will perform repeated measurements which will be used to
check your accuracy and that of the balances.
Results:
Object 1 code =
Balance used
Mass of Object 1
Object 2 code =
Mass of Object 2
Object 3 code =
Mass of Object 3
electronic top-pan
2 decimal place
Brand name
Range & sensitivity
Electronic top-pan
3 decimal place
Brand name
Range & sensitivity
Electronic analytical
4 decimal place
Brand name
Range & sensitivity
Triple beam
Brand name
Range & sensitivity
Questions:
1. Which type of balance do you prefer to use?
Why?
2. Explain why you MUST keep using the same balance for a set of related mass
measurements, from which the analysis results are calculated.
3. Outline the reproducibility of your readings for each object.
4. Which readings did your teacher reject (if any)?
5. Did improvements occur when they were repeated?
Why?
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Student Name:
Practical:
To become familiar with a range of laboratory balances and
assess their performance using a range of unknown and
standard masses
Practical Number:
Date Performed:
Text book References
Results:
Balance
specifications
Mass (g) of
1.0000g
Date Submitted:
5.2 B
Mass (g) of
50.0000g
Mass (g) of
100.0000g
Other Mass
Questions
Write the answers to the textbook questions for this activity below.
Please discuss your answers with your teacher / support staff if you are not sure of what to write.
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Student Name:
Practical:
Practical Number:
Date Performed:
Elementary volume handling and measurements
5.3A + 4.3
Date Submitted:
Text book References
Procedure:
Results:
Read the quantity of liquid present and record in the table below:
Vessel name
Volume
How accurate is your measurement?
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Student Name:
Practical:
To become familiar with a range of laboratory volumetric devices
and assess their performance using simple calibration
procedures
Practical Number:
Date Performed:
Date Submitted:
Text book References see text book 5.3 B and 5.3 C
Result table for 5.3B
Name of volumetric
device
Sacrificial rinse
Fill and adjust to
zero / designated
volume
Deliver specified
volume
Pipette
Burette
Volumetric flask
Not applicable
Not applicable
Teacher sign off
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Result table for 5.3C
Temperature
= _______________
Density of water
=________________
Name of volumetric
device
First
attempt
Second
attempt
Third
attempt
Fourth
attempt
First
attempt
Second
attempt
Third
attempt
Fourth
attempt
Measuring Cylinder
Empty container mass
(g)
Container plus water
mass (g)
Mass of water
(g)
Volume of water
(mL)
Absolute error
Relative error
Stated tolerance
Name of volumetric
device
Beaker
Empty container mass
(g)
Container plus water
mass (g)
Mass of water
(g)
Volume of water
(mL)
Absolute error
Relative error
Stated tolerance
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Name of volumetric
device
First
attempt
Second
attempt
Third
attempt
Fourth
attempt
First
attempt
Second
attempt
Third
attempt
Fourth
attempt
Volumetric Flask
Empty container mass
(g)
Container plus water
mass (g)
Mass of water
(g)
Volume of water
(mL)
Absolute error
Relative error
Stated tolerance
Name of volumetric
device
Burette
Empty container mass
(g)
Container plus water
mass (g)
Mass of water
(g)
Volume of water
(mL)
Absolute error
Relative error
Stated tolerance
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Name of volumetric
device
First
attempt
Second
attempt
Third
attempt
Fourth
attempt
Pipette
Empty container mass
(g)
Container plus water
mass (g)
Mass of water
(g)
Volume of water
(mL)
Absolute error
Relative error
Stated tolerance
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Calibrating an Autopipette
Stated Vol (uL)
= _______________
Temperature
= _______________
Density of water
=________________
Total Mass (g)
Empty sample
vial
1
Difference (g)
------
2
3
4
5
6
7
8
9
10
Average (g)
------
Avg (mL)
------
Amount in uL
(Avg x 1000)
------
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Student Name:
Practical:
Simple Solution Preparation
Practical Number: 5.4A
Date Performed:
Date Submitted:
Text book References
Procedure:
Results:
Potassium Hydrogen Phthalate (Labelled as KHP) – 1.0g +- 0.1g
Your Solution readings
Standard Sample readings
Sample mass:
Sample volume:
pH reading
Conductivity
Potassium chloride (labelled as KCl) – 5.0g +- 0.5g
Your Solution readings
Standard Sample readings
Sample mass:
Sample volume:
RI
Conductivity
Potassium Dichromate (labelled K2Cr2O7) – 0.1g +- 0.01g - needs sulfuric acid added
Your Solution readings
Standard Sample readings
Sample mass:
Sample volume:
Absorbance
@ 450nm
Questions:
1. Why is it important that an analytical balance is used to measure the mass?
2. Why is it important that the transfer of solid material is quantitative?
3. Why was a volumetric flask specified in each case?
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Student Name:
Practical:
Advanced work with solution preparation – Serial dilution
Practical Number: 5.4B
Date Performed:
Date Submitted:
Text book References
Procedure:
follow the procedure outlined in the textbook
Results:
Sodium chloride
Original
solution
Sample mass:
(target 0.254g)
Sample
volume:
100mL
Serial
dilution
details
Volume taken
for dilution
Final
diluted
volume
Solution
concentration
(ppm)
Your Solution
readings
Standard Sample
readings
Cond.
Cond.
Your Solution
readings
Standard Sample
readings
1000 Na
Solution
concentration
(ppm)
Dilution 1
100
Dilution 2
10
Dilution 3
1
Dilution 4
0.1
Hydrochloric Acid
Original
solution
1M
Serial
dilution
details
Sample
mass:
n/a
Volume
taken for
dilution
Sample
volume:
100 mL
Final
diluted
volume
Solution
concentration
(molarity)
pH
Cond.
pH
Cond.
1M
Solution
concentration
(molarity)
Dilution 1
0.1M
Dilution 2
0.01M
Dilution 3
0.001M
Dilution 4
0.0001M
Conductivity tells you how well electricity can flow through the solution – how many ions and how able
they are to carry a current.
pH tells you how acidic the solution is – how many hydrogen ions are available.
These measurements relate – in a linear fashion - to chemical concentration.
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Questions:
1. What trends did you notice for your conductivity results.
(hint: when an ionic solution is diluted to half its concentration, we expect to see half the
conductivity)
2. What trends did you notice for your pH results.
(hint: when an acidic solution is diluted to one tenth its concentration, we expect to see a full
pH unit increase)
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Student Name:
Practical:
Simple filtration
Practical Number: 5.5A
Date Performed:
Text book References
Procedure:
Date Submitted:
As per laboratory manual.
Results:
Identity of solution 1
Volume of solution 1 used
Identify of solution 2
Volume of solution 2 used
Mass of empty filter paper
Mass of filter paper + precipitate
Mass of precipitate
Questions:
1. When is filtration a suitable method of separation?
2. One of the solutions you worked with contained lead. Why is it necessary to be
extremely careful when working with this chemical? How would you find out the
necessary safety requirements for working with lead solutions?
3. Why was it necessary to stir the solution over a water bath?
4. Why was it necessary to allow the solution to cool before filtration?
5. When filtering the solution is not filled to the top of the filter paper, why?
6. Draw a diagram to represent the simple filtration apparatus.
List all the possible places where losses may have occurred.
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Student Name:
Practical:
Comparison of types of Filtration and Centrifugation
Practical Number: 5.5B
Date Performed:
Date Submitted:
Text book References See p36-39 and p55-56 for overview of equipment and how to use it.
Keywords for assessment purposes.
Define: filtration, filtrate, residue, decantation, supernatant, Buchner funnel, Gooch
funnel, Hirsch funnel, sintered glass crucibles, membrane filtration, centrifugation.
Discuss; grades of paper, vacuum filtration, folding of papers, basic rules for
centrifugation.
Filter paper folding techniques
Follow the teacher’s demonstration and supply one of each of the following for
approval
Conical fold approval
Fluted paper approval
Teacher’s signature
Comparison of separation efficiencies
You will be organised into teams to perform a study of different separation
techniques for solid / liquid separations for at least two of the following systems.
You will need to report on relative speed (use a stop watch to time the collection of
1mL of filtrate), effectiveness (assess the cloudiness or clarity of your filtrate) and
efficiency (a combination of how well and how conveniently and how quick it worked)
Calcium
carbonate
Copper hydroxide
Muddy water
Orange juice
Conical folded
qualitative paper
Vacuum
filtration
Fluted paper
Code…
Fluted paper
Code…
Centrifuge
appearance
Ease of decantation
after centrif.
Ease of Pasteur
pipette removal
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Student Name:
Practical:
Application of heating equipment
Practical Number:
Date Performed:
Date Submitted:
Text book References
Procedure:
Task 1
1. Unscrew the stack on each of the supplied burners and examine the features of
each burner. Note the gas jet or nipple and the rotatable sleeve which admits air
and mixes it with the gas as they moves up the stack.
2. Attempt to light the gas at the nipple. Note - the gas supply may need to be very
low for this.
3. Replace the stack and light the Bunsen as demonstrated by your teacher.
4. Note the effect of sleeve positioning on the appearance of the flame.
5. Using the blue flame, turn the gas pressure down slowly so that the flame gets
smaller and strikes back down the stack to burn at the gas nipple.
This condition is extremely dangerous because:
• the Bunsen appears to be off and hence is a fire hazard
• the stack will be heated by the flame and will burn anyone who touches it
6. Repeat the above five steps with the Meker and micro-burners.
Results:
Draw and label a Bunsen and discuss your observations below
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Task 2
Use the supplied thermocouple to measure the temperature of various zones in both
the ‘blue’ and ‘yellow’ versions of the Bunsen flame.
Complete the following table:
Zone of the flame
being measured
Yellow Flame
temperature
Blue Flame
temperature
Diagram to locate each
zone
Approx. 20cm
above the tip of
the flame
At the tip of the
flame
20
cm
In the heart of the
flame
(top of blue cone)
Level with the
stack opening
Task 3
This section is designed to investigate the changes which occur to the gas mixture in
the flame.
Following the demonstrations given by your teacher, examine the presence of zones
of unburnt gases in a Bunsen burner as follows:
1. use a thin glass tube inserted directly into the bottom of the blue cone to tap off
some of its contents – attempt to ignite the gases at the other end of the tube
2. pierce a live match with a pin inserted at right angles approximately half way
along the match – suspend this match with its head pointing up, on the stack of
an unlit Bunsen. Light the Bunsen, with the air hole open.
Results:
For parts 1 and 2 record your observations and your explanations of what is
happening.
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Task 4
This section tests the efficiency of heating water in various containers with different
heating equipment. You are to report on:
• the time taken for the water to boil
• the amount of heating control you have
• the safety of the method.
Each of the containers should be about one third filled and heated as shown by your
teacher.
Container
Heating device
Time to boil
(sec)
Controllability
or efficiency
Safety hazards
micro test tube Bunsen
micro test tube micro burner
test tube
Bunsen
test tube
micro burner
boiling tube
Bunsen
boiling tube
micro burner
Beaker
(100 - 150mL)
Beaker
(100 - 150mL)
Beaker
(100 - 150mL)
Beaker (100 150mL)
Bunsen
micro burner
steam bath
electric hotplate
Questions:
What is the major safety hazard when boiling liquids in test tubes?
Which of the following would be suitable to heat water to boiling?
•
•
•
•
heating mantle
muffle furnace
laboratory drying oven
hair drier
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Student Name:
Practical:
Practical Number:
Date Performed:
Temperature Calibration
5.7A
Date Submitted:
Thermometer 1
Thermometer 2
Identification (if any)
Temperature Range
Reading in ice water
( 0 degrees C)
Reading in Boiling
water
( 100 degrees C)
Reading in dry ice/
acetone mixture
( -78 degrees C)
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