Anions
Illinois Central College
CHEMISTRY 132
Laboratory Section: _______
Page 1
Name:___________________________
Anion Analysis
Equipment
1-tray of dropper bottles
2-wooden test tube blocks
12-16 micro test tubes
2-10 mL beakers
2-micro spatulas
4-medicine droppers
2-micro test tube brushes
1-small graduated cylinder
Make labels for 6 dropper bottles and fill them with the following solutions:
6 M HCl
6 M HNO3
6 M HC2H3O2
6 M NaOH
6 M NH4OH
distilled water
Make 6-8 capillary droppers and 2-3 stirring rods.
Helpful tips
Centrifuge
In order to facilitate the separation of solid precipitate from supernatant liquid, a sample must be
centrifuged. For the centrifuge to spin smoothly, it must be balanced. Be sure to place a like test
tube with approximately the same amount of liquid just opposite your sample tube.
Complete Precipitation
When instructions require that a solution be made alkailne or acidic (in order to precipitate
selected ions) , be sure that you've added enough acid or base by swabbing a drop of the solution
across a strip of litmus paper. Litmus turns blue when exposed to basic solutions and red when
exposed to acidic solutions. Then THROW THE LITMUS PAPER AWAY.
Drop Size
It should be noted that the drops delivered by a cpillary pipette are much smaller than a medicine
dropper. When instructed to add a given number of drops of unknown or a necessary reagent, be
sure to use a medicine dropper for big healthy drops.
Saftey Precautions
Some unknowns contain solutions that may stain the skin. Treat them with care. The
concentrated acids and bases will naturally cause skin irritations or burns, so if you should
contact them, wash the solution off immediately.
Anions
Page 2
Tests for Common Anions
Pre-test: To several drops of the unknown sample, add 2 drops of BaCl2 solution. Then, to a second sample, add 2
drops of AgNO3 solution. These are results obtained with some common anions. (NR= no reaction)
Cl-1
Br-1
I-1
NR
NR
NR
NO3-1
C2H3O2-1
White
White
White
precipitate. precipitate. precipitate.
Insoluble Soluble in Soluble in
in HCl.
HCl
HCl.
NR
NR
Yellow
White
Pale
White
Yellow
precipitate. precipitate. precipitate. precipitate.
yellow
Soluble in precipitate.
(maybe)
Slightly
NH4OH.
soluble in Insoluble Soluble in Soluble in Soluble in
in HNO3
HNO3.
Insoluble
NH4OH.
HNO3
HNO3.
Insoluble
in HNO3
in HNO3.
NR
Colorless
(white)
crystals.
(may form
slowly.
BaCl2
test
White
AgNO3
precipitate.
test
SO4-2
PO4-3
CO3-2
Chloride test
To 2 drops of solution add 1 drop of AgNO3. A white precipitate that
dissolves completely in 6M NH4OH, then reappears when 6M HNO3 is
added confirms Cl-1 ion.
Bromide test
To 3 drops of solution add 6 drops of CCl4. Then add 2 drops of 6M
H2SO4 and 3 drops of chlorine water. Shake tube gently. An orange color
the CCl4 (bottom) layer confirms Br-1 ion.
in
Iodide test
Repeat the test for bromide ion. A pink to purple color in the CCl4 layer
confirms I-1 ion.
Sulfate test
To 2 drops of solution add 2 drops of BaCl2. A whicte precipitate that does
not dissolve in 6M HCl confirms SO4-2 ion.
Phosphate test
To 2 drops of solution add 3 drops of 6M HNO3 and 3 drops of
ammonioum molybdate solution. Heat in a water bath. A fine yellow
precipitate confirms PO4-3 ion. (AsO4-3 also gives test.)
Carbonate test
To 2 drops of solution add 2 drops of 6M HCl. Evolution of a colorless,
odorless gas (bubbles) confirms CO3-2 ion.
Nitrate test
To 3 drops of solution add 3 drops of FeSO4. Holding the test tube at a 45o
angle, allow 5-6 drops of conc. sulfuric acid to flow down the inside of the
tube. Formation of a brown ring at the junction of the two liquids confirms
NO3-1 ion.
Acetate test
To 3-4 drops of solution add 3 drops of conc. sulfuric acid and 3 drops of
ethyl alcohol. Carefully heat in a flame until gentle boiling begins. A fruity
(apple-like) odor of ethyl acetate confims C2H3O2-1 ion.
Anions
Illinois Central College
CHEMISTRY 132
Laboratory Section: _______
Name:___________________________
REPORT SHEET
Analysis of Unknown-Anions
1. Unknown Sample Number _____________
Reagent Added
Result
Conclusion
1.
2.
3.
4.
5.
Sample Contains:_____________
1. Unknown Sample Number _____________
Reagent Added
Result
Conclusion
1.
2.
3.
4.
5.
Sample Contains:_____________
1. Unknown Sample Number _____________
Reagent Added
Page 3
Result
1.
2.
3.
4.
5.
Sample Contains:_____________
Conclusion
Anions
Page 4