Vernier Software and Technology
Vernier Software & Technology

Determining the Quantity of Iron in a Vitamin Tablet


As biochemical research becomes more sophisticated, we are learning more about the role of metallic elements in the human body. For example, copper and zinc are present in enzymes, and trace amounts of molybdenum and selenium are vital in regulating internal oxidation-reduction reactions. Iron is necessary for oxygen transport in the bloodstream. Many people gain these essential elements through their diets, or by taking multivitamin tablets.

The iron that is present in these tablets is in the form of water-soluble Fe2+ ions. In this experiment, you will use the Colorimeter or Spectrometer to determine the quantity of iron in a vitamin tablet. You will prepare four solutions of known Fe2+ concentration. The Colorimeter or Spectrometer will be used to determine the absorbance of each solution at a specific wavelength of light. When a graph of absorbance vs. concentration is plotted for these solutions, a direct relationship should result (Beer’s law).

You will also use a Colorimeter or Spectrometer to measure the absorbance of a solution prepared from a multivitamin tablet. This absorbance value is converted to concentration using the Beer’s law curve. From this concentration, the total mass of iron in the original tablet can be calculated.

The iron in each tablet tested will be reacted with 1,10 phenanthroline so that it develops a detectable color. Sodium acetate and hydroxylamine hydrochloride are added to control the pH of the mixtures and keep the iron in the +2 oxidation state.


In this experiment, you will

  • Prepare Fe2+ standard solutions.
  • Measure the absorbance of each standard solution.
  • Plot a graph of absorbance of Fe2+ vs. concentration.
  • Use a sensor and your Beer's law plot to determine the quantity of iron in a vitamin tablet.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Option 1

Option 2

Option 3

Option 4

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Standards Correlations

See all standards correlations for Chemistry with Vernier »

Chemistry with Vernier

See other experiments from the lab book.

1Endothermic and Exothermic Reactions
2Freezing and Melting of Water
3Another Look at Freezing Temperature
4Heat of Fusion of Ice
5Find the Relationship: An Exercise in Graphing Analysis
6Boyle's Law: Pressure-Volume Relationship in Gases
7Pressure-Temperature Relationship in Gases
8Fractional Distillation
9Evaporation and Intermolecular Attractions
10Vapor Pressure of Liquids
11Determining the Concentration of a Solution: Beer's Law
12Effect of Temperature on Solubility of a Salt
13Properties of Solutions: Electrolytes and Non-Electrolytes
14Conductivity of Solutions: The Effect of Concentration
15Using Freezing Point Depression to Find Molecular Weight
16Energy Content of Foods
17Energy Content of Fuels
18Additivity of Heats of Reaction: Hess's Law
19Heat of Combustion: Magnesium
20Chemical Equilibrium: Finding a Constant, Kc
21Household Acids and Bases
22Acid Rain
23Titration Curves of Strong and Weak Acids and Bases
24Acid-Base Titration
25Titration of a Diprotic Acid: Identifying an Unknown
26Using Conductivity to Find an Equivalence Point
27Acid Dissociation Constant, Ka
28Establishing a Table of Reduction Potentials: Micro-Voltaic Cells
29Lead Storage Batteries
30Rate Law Determination of the Crystal Violet Reaction
31Time-Release Vitamin C Tablets
32The Buffer in Lemonade
33Determining the Free Chlorine Content of Swimming Pool Water
34Determining the Quantity of Iron in a Vitamin Tablet
35Determining the Phosphoric Acid Content in Soft Drinks
36Microscale Acid-Base Titration

Experiment 34 from Chemistry with Vernier Lab Book

<em>Chemistry with Vernier</em> book cover

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