Nitration of Cobalt(Iii) Acetylacetonate
Rossi/Kuwata
Chemistry 222
Spring 2011
Experiment 2: Spectrophotometric Determination of Iron in Vitamin Tablets
(Adapted from Daniel C. Harris’ Quantitative Chemical Analysis and R. C. Atkins, Journal of Chemical Education 1975, 52, 550.)
Experimental work to be done on February 24 + one hour scheduled on your own Notebook due on March 4 (by 4:00 pm ⇒ 20% late penalty each 24 hour period thereafter)
INTRODUCTION
In this experiment, you will dissolve the iron in a vitamin supplement tablet, digesting the cellulosic matrix in the process, and then reduce the iron to Fe2+ with hydroquinone:
While freshly-dissolved aqueous Fe2+ is nearly colorless, we can impart an intense red color by a stoichiometric reaction of Fe2+ with three molecules of the ligand 1,10-phenanthroline (phen):
The absorption spectrum of the complex, often written as Fe(phen)32+, has a maximum at about 510 nm. This complex is stable indefinitely at pH values of 3 or higher. Measuring the analyte solution's absorbance at λmax is a sensitive method for determining iron concentrations. You will prepare a series of standard solutions containing known concentrations of Fe(phen)32+, as well as a solution with Fe from a vitamin tablet, and measure their absorbances on the Chemistry Department’s Beckman DU7400 spectrophotometer. Construction of a calibration curve using your standard solutions will allow you to determine both the molar absorptivity of the Fe(phen)32+ complex and, with a pair of measurements of the iron tablet solution's absorbance under the same conditions, the mass of iron that was present in your vitamin tablet.
WASTE DISPOSAL
All solutions from this experiment can go down the drain.
Page 1 of 8
Rossi/Kuwata
Chemistry 222
Spring 2011
SAFETY
• The hot HCl you are using in this experiment will release corrosive fumes, and will rapidly eat into any organic material with which it comes in contact. Wear gloves while working around the hot acid, and heat it only in a fume hood.
Chemistry 222
Spring 2011
Experiment 2: Spectrophotometric Determination of Iron in Vitamin Tablets
(Adapted from Daniel C. Harris’ Quantitative Chemical Analysis and R. C. Atkins, Journal of Chemical Education 1975, 52, 550.)
Experimental work to be done on February 24 + one hour scheduled on your own Notebook due on March 4 (by 4:00 pm ⇒ 20% late penalty each 24 hour period thereafter)
INTRODUCTION
In this experiment, you will dissolve the iron in a vitamin supplement tablet, digesting the cellulosic matrix in the process, and then reduce the iron to Fe2+ with hydroquinone:
While freshly-dissolved aqueous Fe2+ is nearly colorless, we can impart an intense red color by a stoichiometric reaction of Fe2+ with three molecules of the ligand 1,10-phenanthroline (phen):
The absorption spectrum of the complex, often written as Fe(phen)32+, has a maximum at about 510 nm. This complex is stable indefinitely at pH values of 3 or higher. Measuring the analyte solution's absorbance at λmax is a sensitive method for determining iron concentrations. You will prepare a series of standard solutions containing known concentrations of Fe(phen)32+, as well as a solution with Fe from a vitamin tablet, and measure their absorbances on the Chemistry Department’s Beckman DU7400 spectrophotometer. Construction of a calibration curve using your standard solutions will allow you to determine both the molar absorptivity of the Fe(phen)32+ complex and, with a pair of measurements of the iron tablet solution's absorbance under the same conditions, the mass of iron that was present in your vitamin tablet.
WASTE DISPOSAL
All solutions from this experiment can go down the drain.
Page 1 of 8
Rossi/Kuwata
Chemistry 222
Spring 2011
SAFETY
• The hot HCl you are using in this experiment will release corrosive fumes, and will rapidly eat into any organic material with which it comes in contact. Wear gloves while working around the hot acid, and heat it only in a fume hood.