How to Test for Nitrogen in Water


Normally nitrogen found in water will be in the form of nitrates and water-soluble salts that contains the negatively charged nitrate ion. In order to test the content of nitrogen in water, you can simply do a simple test like diphenylamine test. The test will confirm whether there is any presence of nitrates in the water or not. Another option that you can use is by using an inexpensive field test kit that can sense inorganic forms of nitrogen, which is available for plants like nitrate (NO3-), nitrite (NO2-), and ammonium (NH3).

To test for nitrogen in water, you need:

  • Goggles, gloves, long-sleeved coat
  • 200 mL graduated cylinder
  • Diphenylamine
  • Spatula and scale
  • Distilled water
  • Concentrated sulfuric acid
  • Plastic corrosion-resistant bottle (e.g., HDPE)
  • Glass container (e.g. ashtray, glass)
  • Pasteur pipette

Testing for Nitrogen in Water

How to Test for Nitrogen in Water

  • First thing that you need to do is to protect yourself before starting any of the task or any kind of chemicals
    • Always wear long pants, closed-toed shoes, gloves, chemical splash goggles and a long-sleeved coat.
    • Do not allow the concentrated sulfuric acid to come into contact with your skin. It can cause severe burns to the skin.
    • Make sure that your work area is very well ventilated.

Always be extremely careful when using sulfuric acid because it is extremely toxic and corrosive. If you do not have any experience dealing with the chemicals, it is advisable for you not to perform the task.

  • The next step is for you to weigh approximately 0.5 grams of diphenylamine
    • Then, add the diphenylamine into a graduated cylinder
    • Pour 20 mL of distilled water
    • Stir and swirl the mixed solution together until it dissolves
  • Then, add very gently some sulfuric acid to the mixture so that the volume of the acid will increase to 100mL.
    • Concentrated sulfuric acid will produce substantial heat whenever it comes into contact with water.
    • You do not have to add any more water or other chemicals after this.
  • After that, you can pour the solution into a corrosion-resistant plastic bottle
    • Store the solution in a dark cool area and ensure that it is kept away from heat.
  • For the testing of nitrogen, you need to place up to 15 drops of water into your glass container.
  • Drop a few of the reagent that you have prepared and you should watch the color of the solution.
    • If the solution turns into a deep blue in 30 minutes or less, there is a high level present of high nitrates.
    • Nitrates can be present at trace level.

      Always remember that if you are testing for nitrogen in water,

      • Apart from using the above steps, you can send sample to your lab and get them to check the water condition by using more sophisticated equipment.
      • Always do your testing in a well ventilated area. It is much better if you have an area equipped with a fume hood.

Fun Fact

  • Do not supply your trees, shrubs and lawns with high doses of nitrogen. Always use iron or even potassium.
  • Nitrogen is important and has essential nutrients to produce a lush lawn. Nitrogen is needed because it is a building block of many plant proteins that will help produce a healthy looking lawn. You will need to apply a nitrogen fertilizer to replenish your soil if the lawn look discolored or if the growth of the lawn is slow. Clovers will help to fix the atmospheric nitrogen and store it to maintain health. This will ensure a healthy looking lawn.
  • The importance of pH reading will determine the level of certain nutrients such as potassium and nitrogen, which is essential for the growth of some plants. The higher the level of nitrogen available to plants, the more level of alkaline in the soil.
  • After establishment, do not give your plants on the fence too much nitrogen as it will make difficult for you to prune them. You could also use your fence to produce food such as strawberries, tomatoes and string beans.
  • The bad thing about leaving tree stumps on your land is that they suck the nitrogen content from the soil.
  • Trees require nitrogen, phosphate and potash to enable them to flourish.
  • Nitrogen, phosphorus and potassium are the three main components in plant nutrition. Nitrogen is important for the propagation of healthy foliage and stem growth. Nitrogen bioavailability is made via nitrogen fixing bacteria that act by converting nitrogen into nitrates that can be used by plants. An adequate amount of nitrogen is required by the soil as it is used up by plants, disappears with decay and gets washed out from the soil as it is water-soluble. An over excessive amount of nitrogen can cause too much foliage growth and reduce the growth of flowers and fruit.

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