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Fractionation (Fractional Distillation) of Essential oils (Part 1).

  • Writer: Essential Stills
    Essential Stills
  • Nov 17, 2022
  • 2 min read

Updated: Apr 28, 2025

Typical Fractionation Still. For clarification purposes

support framework and clamps have been omitted.

Place flange flask in a suitable support (e.g. a cork ring) and add the required weight of essential oil to be distilled. It is usual to roughly half fill the flask, so if a 10L flask is to be used, then about 5000g of essential oil is about right.

The flask is then placed in the mantle and this should be sited immediately in front of the stainless steel support rack that has been securely affixed to the wall at the correct height (not shown). The flange of the flask should then be well greased and the flanged lid affixed. The stainless steel clip can then be securely fitted in place. Any spare sockets in the flange lid (excluding the ones that are to be used for the bleed and the column) should be sealed with the appropriate stoppers and all glass joints should be well lubricated with an appropriate silicon grease.

Fix the pre-filled column (see following blogs) into the central greased socket within the lid and support it using one of the clamps that are fixed to the wall support racking.

Make the bleed (see following blogs) and fit into a suitable side socket in the flange lid. The end of the capillary should be within a millimetre or two of the bottom of the flask. For more reactive essential oils, it is best to fix a short length of rubber tube on to the spigot at the top of the bleed: fix the other end of the rubber tube on to the side spigot on the 250ml Büchner flask. Place about 50 - 100ml of highly volatile unreactive solvent e.g. hexane into the Büchner flask and affix the greased socket into the top cone. This system prevents air entering the distillation and is required for those oils where this air entry could cause oxidation issues. However, it still allows the bleed to operate and this, in turn, will stop any ‘bumping’ during the boiling process.

For less sensitive oils, it should be acceptable to simply allow air to flow through the bleed to stop any 'bumping' occurring.

Grease the cone and affix the reflux dividing head and condenser onto the socket at the top of the column and secure with a clamp, ensuring the divider is set to the fully closed position. Grease the cone and affix the thermometer into the side socket in the variable reflux dividing head.

Insert the outlet cone of the dividing head into the side socket of the Perkins triangle and clamp securely, ensuring that all components are correctly aligned. Fix a 100ml round bottomed flask on to the base of the Perkins triangle and clamp in place for the time being: it will subsequently be held in place by the vacuum during the distillation process itself.

Affix vacuum pipe tubing on to the Perkins triangle with a second linked branch also going to the spigot situated on the side of the variable reflux dividing head, to enable it to evacuate the entire glass apparatus throughout the distillation.

The apparatus is now ready for operation.

See our next blog for the next stage of the fractionation.


 
 
 

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More Information

 

 

What is it?

 

This Still comprises a boiling vessel with 6 elements at the base and a basket inside. A tall steam collection cone is fitted on top of the boiling vessel that carries a bend at its top that then joins onto an open horizontal 4” tube. This tube ends in a 90° bend that points downwards and this then joins on to the condenser with a 4” screw fitting.

 

​The condenser is a beautiful piece of kit with 36 narrow (8mm) thin-wall tubes fitted equidistantly within a 4” diameter stainless outer tube: there are 3 sets of baffles fixed at set intervals to make the water ‘chicane’ and maximise agitation and therefore improve its cooling capability. There is a cone at the base of the condenser to direct the distillate into the glass Florentine fitted directly underneath.​

 

How it Works:

 

The water boils, the dry steam goes through the plants in the basket collecting a bit of essential oil on the way and continues up the cone: at the top it turns 90°, goes through the top pipe and then heads down through the 36 pipes in the condenser. Since these pipes are surrounded by cold water, the steam then condenses into liquid and drops into the glass Florentine that is placed underneath. Here any oil present will separate and float to the surface, while the condensed water then trickles back to the boiling vessel via the S trap mounted a few inches up from its base.

 

​How to Operate:

 

Lift off cone/condenser unit and slide to one side and remove basket. Fill vessel with 40 - 50 litres of water, enough to cover the elements with say, an inch of water on top. Line basket with muslin and fill it with the material you want to distil e.g. lavender - and place it back inside the boiling vessel. Some form of lifting apparatus will be required e.g. simple sliding block and tackle. ​Slide cone/condenser unit back and lower onto boiling vessel, lock the clamps so that it all becomes one unit and turn on the heat. The Still has a wrap-around fabric insulation jacket made in two sections and one goes over the cone whilst the other goes around the boiling vessel. As the Still heats up, you can turn off some of the elements until a nice rolling boil is achieved. Make sure water is gently flowing through the condenser to keep it cold and the distillation continues until the oil layer in the Florentine stops growing. Then turn off heat and water and remove oil.

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