Modern inorganic chemistry

GROUP V 225

Hydrazoic acid behaves as both an oxidising and reducing agent

in solution. Thus it will oxidise hydrochloric acid to chlorine, the

main products being nitrogen and ammonium ions:

HN 3 + 3H+ + 2C1" -» C1 2 T 4- NH^ + N 2 T

On the other hand, chloric(I) acid, for example, oxidises hydrazoic

acid to nitrogen:

2HN 3 + ocr -» 3N 2 T + cr -h H 2 o

The azides are salts which resemble the chlorides in solubility

behaviour, for example silver azide, AgN 3 , is insoluble and sodium

azide, NaN 3 , soluble in water. Sodium azide is prepared by passing

dinitrogen oxide over molten sodamide:

2NaNH 2 + N 2 O -> NaN 3 + NaOH + NH 3

All the azides are potentially dangerous, and liable to detonate

on heating, but those of the alkali and alkaline earth metals can be

heated with caution if pure; they then evolve pure nitrogen.

Hydrides of phosphorus

PHOSPHINE

Phosphine can be prepared by the reaction of a strong alkali with

white phosphorus; potassium, sodium and barium hydroxides may

be used:

P 4 4- 3KOH + 3H 2 O -> 3KH 2 PO 2 4- PH 3 T

potassium

phosphinate

(hypophosphite)

This reaction gives an impure product containing hydrogen and

another hydride, diphosphane, P 2 H 4.

Pure phosphine can be prepared by the reduction of a solution

of phosphorus trichloride in dry ether with lithium aluminium

hydride:

4PC1 3 + 3LiAlH 4 -> 4PH 3 T + 3LiCl 4- 3A1C1 3

The reaction of potassium hydroxide solution with phosphonium
iodide also gives pure phosphine:

PH 4 I + KOH -> KI 4- H 2 O + PH 3 T