1. Tecknology and Engineering
CHEMICAL ANALYSIS

2. Determination of alluminium
SMK Negeri 13 Bandung

3. Bismillahirrahmanirrahiim
Rabbi zidna ilmaan ……..
Oh God, please opened our heart and mind, enlightened with Your light. Godsend of science dot which Thou own to us…
Oh God…
Allow our prayer…
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4. After this session, the students are expected
Objectives….
After this session, the students are expected
to be able :
Explain the steps of determination of alumunium
Explain the objectives of every steps
Explain the functions of reagents
Arrange the planning of determination of alumunium acording
To the job sheet
Conduct determination of alumunium
Do the calculation in determination of alumunium
Arrange the report of the determination of alumunium
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5. Procedure 1. Weigh out accurately about 1,8 gram
Aluminium sample salt.
3. Add pure dilute ammonia solution
Drop wise from a burette until the color
in solution change
To yellow
2. Rinse and dissolve in 200 ml of water than
add5 gr of ammonium chloride
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6. 4. Boil the solution for 1 or 2 minutes and filter
At once through a quantitative filter paper
5. Wash the precipitate thoroughly with hot 2
percent ammonium nitrate or chloride solution
made neutral with ammonia solution to
methyl red indicator.
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7. Discussion 7.Dry, char and ignite for 10-15 minutes
with a Fisher or Meker
high temperature burner. (12000C)
6.Place the paper with the precipitate in a
constant weighed crucible.
Discussion
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8. Discussion….. The aluminium is precipitated as the
hydrated oxide by means of ammonia solution
in the presence of ammonium chloride.
The gelatinous precipitate is washed,
converted into the oxide
by ignition and weighed as Al2O3
aluminium hydroxide is amphoteric in character :
Al(OH)3 + 3H+  Al3+ + 3H2O
Al(OH)3 + 3OH-  AlO H2O
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9. PRECIPATION Begin at pH 4 Complete between pH 6,5 – 7,5.
The pH range adjusted with the aid
of methyl red as indicator.
The pH employed for precipitation
must be controlled
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10. The Ammonium chloride PH controlling as a buffering agent
Assists the coagulation of initially
colloidal precipitate.
Reduces to a minimum co precipitation of
the divalent metal such as calcium and magnesium.
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11. Readily filterable precipitate
Hot precipitation
Readily filterable precipitate
Slow/gradual
Big Size
Co agulated
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12. Washing of precipitate
Use no pure water because aluminium hydroxide will readily peptized and will run through the filter.
Use 2 percent neutral NH4Cl or NH4NO3 solution .
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13. Washing solution…. NH4Cl or NH4NO3
- electrolyte, prevent the peptisation, stabilize the co agulated precipitate
Neutral
- prevent the dissolving reaction to be Al+3 or AlO2-
Hot
- Co agulation
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14. Ignition 2 Al(OH)3 Al2O3 ignited in a silica crucible
- at least 12000C
2 Al(OH)3 Al2O3
ignited in a silica crucible
(porcelain is slightly hygroscopic when heated to a high temperature)
- Use Fisher or Meker burner. (The best procedure is in an electric furnace.)
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15. Ignition aluminium oxide is formed at 9000C, but hygroscopic
A stable and pure aluminium oxide is formed at 12000C
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