Some compounds have very high boiling points. To boil such compounds, it is often better to lower the pressure at which such compounds are boiled instead of increasing the temperature. Once the pressure is lowered to the vapor pressure of the compound (at the given temperature), boiling and the rest of the distillation process can commence. This technique is referred to as vacuum distillation and it is commonly found in the laboratory in the form of the rotary evaporator.

    This technique is also very useful for compounds which boil beyond their decomposition temperature at atmospheric pressure and which would therefore be decomposed by any attempt to boil them under atmospheric pressure.

    一些化合物具有很高的沸點(diǎn)。要使這類化合物沸騰，最好是降低化合物沸騰時的壓力而不是提高溫度。一但壓力降低到化合物的蒸汽壓（在一定的溫度下），化合物就開始沸騰，蒸餾作用就可進(jìn)行。這項(xiàng)技術(shù)被稱為真空蒸餾，且以真空汽化器的形式常見于實(shí)驗(yàn)室。

    這項(xiàng)技術(shù)對于大氣壓下沸點(diǎn)超過其分解溫度的化合物是很有用的，在大氣壓下讓這類化合物沸騰的嘗試，都會使其分解