1. PROCEDURE
Dry resin (8.04g) was placed in a 100ml beaker. Pipetted volumes of distilled water
(20ml) and 8M HCl (5ml) were added. The contents of the beaker were quickly swirled
and poured through a funnel into the burette (column). An additional volume of 8M HCl
(15ml) was added in 5ml portions to the residue in the beaker, the contents swirled and
then quickly added to the burette. The burette was tapped gently to pack the resin. The
volume of the resin and the total volume of the liquid used to transfer it to the column
were recorded. The volume of the stationary phase and the volume of the mobile phase
were then calculated. The solution and an additional volume of 8M HCl (15ml) added
was allowed to flow through the resin to within 1ml above the top of the resin bed. The
flow rate of the burette was set to 1.33cm3min-1 (approximately 2 drops every 3 seconds)
and the burette marked. The length of the resin bed was also measured and recorded. The
column was drained to just above the top of the resin and the tap closed. A pipetted
volume (0.5ml) of the supplied metal ion solution was added directly to the resin then the
column was drained to within 1ml above the top of the resin. 8M HCl (1ml) was added to
rinse any metal ion from the walls of the column and the tap closed. The tap was set to
the required position for the flow rate and 8M HCl (15ml) was added in small quantities
such that the volume of the liquid above the resin remains approximately 1ml. The eluant
was collected in sequentially numbered 10cm3 tubes, pre-marked to indicate the
respective volumes. The first five portions collected were of 3ml volume while the
remainder were of 5ml volume. Following the addition of the 8M HCl (15ml), 3M HCl
(30ml) and distilled water (30ml) were added in small quantities and the fractions
collected continuously. The time taken to collect each eluant and the respective volume
was recorded. A total of seventeen (17) portions were collected. The collected fractions
were stoppered, labelled and stored for use in the next lab session.
Spot tests were carried out on all tubes. The identification of nickel (Ni2+) was done first.
Starting with the tubes labelled 1-5, six (6) drops of eluant was transferred to clean test
tubes. The solutions were neutralised by adding drops of 15M ammonia until they were
just basic to litmus (red litmus changes to blue). 1% dimethylgloxime reagent (0.5ml)
was added and the contents mixed. The formation of a brick-red precipitate would
confirm the presence of Ni (II) ions. The remaining tubes were tested till no more Ni (II)
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2. could be detected. The results were recorded. The test for Cu2+ ions was then carried out
starting with the first five tubes that did not contain nickel. Six (6) drops of eluant was
transferred to clean test tubes. Five (5) drops of phenolphthalein was added followed by
6M ammonia drop-wise until the first faint pink colour was observed. The solution was
neutralised with acetic acid until colourless. 0.2% aqueous diethyldithiocabamate
solution (2ml) was then added. The presence of a yellow colour confirmed the presence
of Cu (II) ions. The remaining tubes were tested till no more Cu (II) could be detected.
The results were recorded. The test for iron was carried out starting with the first five
tubes that did not contain nickel. Six (6) drops of eluant was transferred to clean test
tubes, followed by five (5) drops of KSCN. The formation of a deep red colour confirmed
the presence of Fe (II) ions.
Quantification of metal ion concentrations in the eluant was carried out on those that
tested positive for the respective metal ions. The procedure for iron is as follows: to 2ml
aliquots of the relevant eluants, 10% hydroxylamine hydrochloride solution (1ml), 0.5%
phenanthroline solution (1ml) were added and additions of 2M sodium acetate to adjust
the pH to 2. The solutions were allowed to stand for one (1) hour then diluted with
distilled water (25ml). The absorbances for the eluants were measured at a wavelength of
505nm. The procedure for copper is as follows: to 1ml aliquots of the relevant eluants,
three (3) drops of phenolphthalein was added followed by 6M ammonia drop-wise until
the first faint pink colour is observed. The solution was neutralised wit acetic acid until
colourless. 0.2% diethyldithiocabamate solution (2ml) was then added and the
absorbances measured immediately at wavelength 545nm. The procedure for nickel is as
follows: to 1ml aliquots of the relevant eluants in a 125ml conical flask, saturated
bromine water (0.5ml) followed by 15M ammonia (2ml), 95% ethanol (20ml),
dimethylgloxime solution (10ml) and distilled water (7ml) were added. The absorbances
were measured at wavelength 450nm. The absorbances were measured using the Unicam
5675 visible spectrometer which was zeroed with distilled water each time.
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