Question

How is phosphine prepared in the laboratory?

Answer 1

White phosphorus is frequently heated with a concentrated sodium hydroxide solution in an inert environment of carbon dioxide or oil gas to produce phosphine in a lab setting.

\[\ce{P4 + 3NaOH + 3H2O -> \underset{Sod. hypophosphite}{3NaH2PO2} + PH3}\]

A round-bottom flask with a delivery tube dipping in water and another tube for delivering CO₂ gas into the flask is filled with a few bits of white phosphorus and a concentrated solution of NaOH. Phosphine gas is produced when the flask is heated. Because of the contaminant phosphorus dihydride (P₂H₄), it spontaneously ignites. A sequence of vortex rings of smoke is created as the gas bubbles spontaneously catch fire as they rise above the water's surface. Alcoholic potash can be used in place of NaOH solution to produce pure gas.