Iron in Water

Introduction

The amount of iron in a water sample will be found by using the TesTab^® color comparison method.

Concepts

• Concentration of iron
• Parts per million
• Water testing

Background

Iron, in small amounts, is an essential nutrient to humans and other organisms. It is present in water from natural sources such as rocks and soils and it is also found in water due to industrial waste and the corrosion of iron pipes. When the concentration of iron is above 0.1 parts per million, it will precipitate as iron oxide upon contact with air. Iron oxide will stain laundry, plumbing fixtures and silverware. It will also cause food and drinks to taste and look peculiar. Iron concentrations in drinking water should not exceed 0.3 parts per million.

Materials

Safety Precautions

Total Iron TesTabs^® contain chemicals that may irritate skin, or be harmful if swallowed. The TesTab reagents used in this kit were designed with safety in mind. The single-use, foil-packaged TesTabs are easy to dispense. Store TesTabs in a cool, dry place and only open when ready to use the tablet. A single tablet, either alone or reacted with a sample, is a very low health hazard; however, TesTabs should not be ingested. Wear chemical splash goggles and chemical-resistant gloves. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. In the field, reacted samples may be poured into a container for later treatment. Reacted samples may be flushed down the drain with plenty of water according to Flinn Suggested Disposal Method 26b.

Procedure

1. Fill the water sample tube to the 5-mL line with the tap water sample.
2. Add one Total Iron TesTab to the water sample tube.
3. Cap the tube and mix the solution until the tablet has dissolved.
4. Wait for five minutes.
5. Compare the color of the sample to the Iron color comparison chart.
6. Dispose of the reacted sample according to the instructor and rinse the water sample tube twice with the water sample for the next test.

Teacher Tips

• Enough materials are provided for 15 tests.
  
• It’s a good idea to collect several water samples from each site that is tested. It is also wise to test the samples within one hour of collection if possible.
  
• Total Iron TesTabs^® contain bipyridyl. Iron(III) ions are reduced to iron(II) ions and form a colored complex with bipyridyl that can be used for the overall quantitative measure of total iron.
  
• A wait of five minutes is required for the overall reaction to take place.
  
• The range of the total Iron TesTab is between 0 to 10 ppm.