Synthesis of phosphine

Preparation of pyrophoric gas

Scientific name: Sodium hydroxide reacts with phosphorus and phosphine gas is produced. Then, it ignites in air.



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Chemistry P Block part 19 (Phosphine: Properties, uses, preparation & numerical) CBSE class 12 XII

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Получение и самовоспламенение фосфина


Wear eye protection goggles. Use gloves. Phosphine is a poisonous gas! If possible, use a hood or carry out the experiment outdoors. Flammable substances! Use nonflammable workplace.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

3 NaOH + P4 + 3 H2O → 3 NaH2PO2 + PH3

2 PH3 + 4 O2 → P2O5 + 3 H2O

Step-by-step instruction

WARNING! This experiment is dangerous! You should NOT perform this at home. ONLY carry out this experiment, if you are a trained chemist, and you understand local safety and legal requirements, which are required to perform such experiments

  1. Prepare a concentrated solution of sodium hydroxide. Pour 20 ml of water in a beaker. Slowly add sodium hydroxide to the beaker until alkali is dissolved.
  2. Attach a large test tube to the stand at an angle of 45 degrees. Pour the resulting solution into the test tube.
  3. Carefully place a small piece of white phosphorus into the test tube.
  4. Close the test tube with a stopper equipped with a tap with a tube. Lower the other end of the tube into the evaporation dish with water.
  5. Heat the test tube using an alcohol lamp.
  6. Some time later, bubbles form and burn in air.

Scientific background

Phosphorus, similarly to halogens and chalcogens may disproportionate in presence of alkali, forming phosphine. This reaction proceeds due to the high chemical activity of white phosphorus, which binds with a greater possibility than nitrogen, and the element-element bonds are very weak.

Phosphine has lower values of bond energy R-H, hydrogen bond energy and dipole moment than ammonia. These factors explain the low solubility in water and high chemical activity of phosphine which explains why phosphine ignites in air


Published on 15 May 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst