How to detect potassium nitrate

Written by jennifer simon
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Potassium Nitrate, also known commonly as saltpetre, is used to interfere with drug test results and mask the use of illegal substances such as marijuana. In drug testing, metabolites from marijuana are what is tested and the chemical composition of potassium nitrate destroys the metabolites and makes marijuana usage more difficult to detect. Potassium nitrate is also a key ingredient in gunpowder, fireworks and fertiliser. Testing for the presence of potassium nitrate is relatively simple.

Skill level:

Things you need

  • Platinum or nichrome (nickel-chromium) wire
  • Hydrochloric acid
  • Bunsen burner with hot flame
  • Protective goggles
  • Protective gloves
  • Solution or mixture to be tested

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  1. 1

    Use the hydrochloric acid and flame to clean the wire. Dip the wire into the acid, then into the flame and repeat until the wire does not produce any colour.

  2. 2

    Once you are sure the wire is clean, dip it again in the acid to moisten it. Subsequently dip it into the solid mixture you are testing. Place the wire back into the flame.

  3. 3

    If the colour is weak, repeat step two. A short burst of colour should result. The colour of the flame burst determines what chemicals are present in the mixture.

  4. 4

    Potassium bursts in a bright lilac shade. If potassium nitrate is present in the mixture the lilac will be visible. Blue-violet indicates the presence of caesium, red-violet indicates rubidium.

Tips and warnings

  • To have a base test of potassium nitrate presence, you can use fertiliser or gunpowder as a testing material. Hydrochloric acid is commonly sold as muriatic acid in pool supply stores.
  • When working with chemicals and flames, it is important to use proper equipment, goggles and gloves for safety. Hydrochloric acid is corrosive and should be stored properly. Potassium nitrate is a salt and will cause oxidation, in addition to being used in explosives. It is important to treat all materials with extreme care.

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