GROUP V 253
Antimony(III) halidesAntimony(IIl) fluoride is a readily hydrolysable solid which finds
use as a fluorinating agent. Antimony(III) chloride is a soft solid,
m.p. 347 K. It dissolves in water, but on dilution partial hydrolysis
occurs and antimony chloride oxide SbOCl is precipitated:
[Sb^3 +] + CP + H 2 O ^ 2H+ 4- O=Sb-<:i(Here again the simple formulation [Sb^3 + ] is used to represent all
the cationic species present.) The hydrolysis is reversible and the
precipitate dissolves in hydrochloric acid and the trichloride is
reformed. This reaction is in sharp contrast to the reactions of
phosphorus(III) chloride.
Antimony(V} fluoride is a viscous liquid.
Antimony(V) chloride is a fuming liquid, colourless when pure,
m.p. 276 K. It is a powerful chlorinating agent.Bismuth halides
The trihalides closely resemble those of antimony. Bismuth(V)
fluoride is known. It is a white solid, and a powerful oxidising agent.
TESTS FOR GROUP V ELEMENTS
Nitrogen
For nitrogen gas, there is no test. In a gas mixture, any residual
gas which shows no chemical reaction with any reagent is assumed
to be nitrogen (or one of the noble gases). If a mixture of nitrogen
and the noble gases is passed over heated magnesium, the magnesium
nitride formed can be identified by the ammonia evolved on addition
of water.
Combined nitrogen is usually convertible either to ammonia by
reduction or to a nitrate by oxidation. Hence tests, qualitative or
quantitative, already described can be applied for these.
Phosphorus
Prolonged oxidation of any phosphorus compound, followed by
standing in water, converts it to phosphate(V). This can then be
detected by the formation of a yellow precipitate when heated with