How will you prepare phosphine and explain the purification of phosphine ?

Explanation

Phosphine is prepared by action of sodium hydroxide with white phophorous in an inert atmosphere of carbon dioxide or hydrogen.
`P_(4) + 3NaOH + 3H_(2) O rarr underset("sodium hypo phosphite")(3NaH_(2)PO_(2)) + underset("Phosphine")(PH_(3) uarr)`
Phosphine is freed from phosphine dihydride `(P_(2)H_(4))` by passing through a freezing mixture. The dihydride condenses while phosphine does not.
Phosphine can also prepared by the hydrolysis of metallic phosphides with water or dilute mineral acids.
`{:(Ca_(3)P_(2) + 6H_(2)O,rarr,underset("Phosphine")(2PH_(3)uarr) + 3Ca(OH)_(2)),(AIP + 3HCI,rarr,underset("Phosphine")(PH_(3) uarr) + AlCl_(3)):}`
Phosphine is prepared in pure form by heating phosphorous acid.
`underset("Phosphorous acid")(4H_(3)PO_(3)) overset(Delta)rarr underset("Ortho phosphoric acid")(3H_(3)PO_(4)) + underset("Phosphine")(PH_(3) uarr)`
A pure sample of phosphine is prepared by heating phosphine iodide with caustic soda solution.
`PH_(4)I + NaOH overset(Delta)rarr underset("Phosphine")(PH_(3) uarr) + NaI + H_(2)O`