General Laboratory Technique

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General Laboratory Technique
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Common Apparatus / Equipment
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Common Apparatus / Equipment
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Test tube and Boiling tube
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Test tube holder
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Round-bottomed flask and Flat-bottomed flask
Stronger than the flat-bottomed flask but
clamping is required. Usually used in generating
gas.
Round-bottomed flask
Flat-bottomed flask
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Spatula
- Spoon used in the laboratory.
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Electronic balance
Dont add anything into a weighing bottle over
the pan of the balance. Chemicals may fall onto
the pan.
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Electronic balance
x
Dont add anything into a weighing bottle over
the pan of the balance. Chemicals may fall onto
the pan.
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Heat resistant mat /Fireproof mat
All hot objects MUST be placed on the heat
resistant mat to protect the bench. Especially,
the newly extinguished matches before they are
disposed of.
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Heat resistant mat /Fireproof mat
Put the used matches on the heat resistant mat to
allow them to cool down.
?
X
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Stand and Clamp
For the apparatus that would be subjected to
heating should only be clamped loosely. A little
space should be allowed for the glassware to
expand otherwise it may crack.
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Stand and Clamp
Wrong
Right
The mouth of the clamp should be opening upward,
otherwise the clamp may drop if the clamping is
loose.
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Stand andPlastic burette clamp
Adjusting the position
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Common Laboratory Technique
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Operation of Bunsen burner
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Operation of Bunsen burner
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Operation of Bunsen burner

• Only a non-luminous flame should be used to heat
  glassware. A yellow flame contains unburnt carbon
  particles which will blacken glasswares.
• The used match should be place on the heat
  resistant mat until it is completely extinguished

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Operation of Bunsen burner
Why should the air hole be closed before a burner
is lighted up ?
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Press and turn the knot to turn on the gas supply
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Handling of striking back
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Handling of striking back

• Turn off the gas supply immediately.
• Wait, Wait, Wait, Wait and Wait
• After the collar has cooled down, close the air
  hole and light the burner again.

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Transferring chemical
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Take your apparatus to the chemcial
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Dont take the chemical back to your seat.
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Transferring of solid
Use the smaller end of a spatula only. The larger
end is only for the laboratory technician to
transfer a large amount of chemical. A small
spatula measure of solid weighs about 0.2 to 1
gram, depending on the solid.
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Transferring of solid
Any excess chemical from the reagent bottle
should not be returned to the reagent bottle
otherwise the reagent will be contaminated (get
dirty) NOR putting onto the bench. Put the excess
chemical into the Waste Beaker on the bench, if
you do not see the beaker, ask your teacher or
the laboratory technician.
Waste Beaker
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Transferring of solid
Waste Beaker
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Transferring of solid
Be Carefully ! Try not to drop any chemical onto
the bench.
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Transferring of liquid
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Transferring of liquid
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Mixing solution
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(No Transcript)
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Heating technique
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Heating hydrated solid
The tube should be pointed downward otherwise the
condensed water may crack the bottom due to local
contraction of glass.
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Heating solution in a test tube
Test tube is not for boiling liquid. For every 5
seconds of heating, the tube should be swirled
away from the flame for at least 5 seconds.
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Heating flammable liquid
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Heating flammable liquid
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Heating flammable liquid- no naked flame (????)
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How much water is enough in a steam bath ?
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Problem of using too less water.
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Collection of gas
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Displacement of water
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Delivery of gas / Displacement of air
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Gas syringe
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Prevention of sucking back
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Drying substances
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Desiccator
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Desiccator
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Common Drying agentse.g. anhydrous calcium
chloride
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Common Drying agentse.g. anhydrous calcium oxide
(??)
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Common Drying agentse.g. silica gel (???)
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Washing bottle
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U-tube