Some compounds have high boiling points as well as being air sensitive. A simple vacuum distillation system as exemplified above can be used, whereby the vacuum is replaced with an inert gas after the distillation is complete. However, this is a less satisfactory system if one desires to collect fractions under a reduced pressure. To do this a "pig" adaptor can be added to the end of the condenser, or for better results or for very air sensitive compounds a Perkin triangle apparatus can be used.

    The Perkin triangle, has means via a series of glass or Teflon taps to allows fractions to be isolated from the rest of the still, without the main body of the distillation being removed from either the vacuum or heat source, and thus can remain in a state of reflux. To do this, the sample is first isolated from the vacuum by means of the taps, the vacuum over the sample is then replaced with an inert gas (such as nitrogen or argon) and can then be stoppered and removed. A fresh collection vessel can then be added to the system, evacuated and linked back into the distillation system via the taps to collect a second fraction, and so on, until all fractions have been collected.

    有些化合物不但沸點高，而且對空氣敏感。因而�？墒褂煤唵握婵照麴s系統(tǒng)（如上所舉的例子），蒸餾完成之后，用惰性氣體填充真空。可是，如果想在負(fù)壓下收集餾分這套系統(tǒng)就不能令人滿意。為了在負(fù)壓下收集餾分，可在冷凝器末端加裝一個pig 轉(zhuǎn)接器，或者可采用Perkin triangle設(shè)備，以取得較好的結(jié)果或用于空氣極敏感化合物的蒸餾。

    The Perkin triangle　通過一系列的玻璃或特氟綸閥門使餾分與剩下的蒸餾物隔離，而不用將蒸餾主體與真空或熱源分開，這樣可保持回流狀態(tài)。為了做到這點，首選將樣品與真空用閥門隔開，然后將樣品上面的真空用隋性氣體代替（如氮氣或氬氣），然后塞上塞子移走。這時可將新的收集容器連接到系統(tǒng)上，再通過閥門退下來后再次連接到蒸餾系統(tǒng)內(nèi)以收集二次餾分。就這樣直至收集完全部餾分。