Tetraborodecahydride, B₄H₁₀

Tetraborodecahydride or borobutane, B₄H₁₀, is a colourless, very volatile liquid which boils at 16° to 17° C., and freezes at about -112° C. The vapour density is 27.0 (H = 1), in accordance with the formula given. The vapour pressures at various temperatures are as follows: -

Temp. °C.	0°	6°	10°	15°	16°
Vap. press, (in mms.)	500	580	630	710	740

The hydride has a very disagreeable odour. A few bubbles when inhaled affect respiration and cause headache. It is extremely unstable, decomposing in a few hours at ordinary temperatures into a series of other hydrides. It is decomposed by electric sparks, and ignites spontaneously in air or oxygen, burning with a green flame. Nitric acid oxidises it with explosive violence.

It is slowly decomposed by water, the final result being expressed by the equation: -

B₄H₁₀ + 12H₂O = 4H₃BO₃ + 11H₂.

Aqueous sodium hydroxide rapidly and completely absorbs the hydride, producing a hypoborate, but hydrogen is slowly evolved, and the net result may be expressed thus: -

B₄H₁₀ + 4NaOH + 4H₂O = 4NaBO₂ + 11H₂.

The hydride is decomposed by alcohol and reacts with ammonia, but its solution in benzene is very stable towards oxygen.