How many theoretical plates does a Vigreux column give?

A Vigreux column typically delivers 0.5 to 1.5 theoretical plates per 20 cm of length, so a 30 cm column is usually worth roughly one to two plates and a 60 cm column three to five plates, depending on boil-up rate and vacuum. Plate count falls sharply if the column is run above its flooding point or is not insulated, which is why the same column can perform well on one duty and poorly on another.

Vigreux or packed column — which should I choose?

Choose Vigreux for dirty, crystallising or high-boiling samples, for teaching, and for duties where cleaning and repeatability matter more than maximum efficiency, because it has no packing to replace or channel. Choose a packed column with glass helices, Raschig rings or structured packing when you need more plates per unit length and the sample is clean enough that the packing will not foul.

What reflux ratio should I run?

As a starting point use 2:1 to 5:1 for close-boiling mixtures and 1:1 for easy separations; higher reflux gives sharper cuts but takes longer and puts more heat through the column. Set the ratio with a timed solenoid or a manual stopcock, hold it constant through the cut, and accept that the first fraction will always be contaminated by hold-up from the previous run.

Fractionating Columns and Vigreux Columns Singapore

Q: Does JWRESEARCH supply fractionating columns in Singapore?

Yes. JWRESEARCH supplies borosilicate 3.3 Vigreux columns, plain and vacuum-jacketed columns, packed columns with helices or rings, column heads with reflux splitters, silvered vacuum jackets, and matching still heads and condensers, delivered across Singapore with joint-size matching support.

Published: {{NEW_ARTICLE_DATE}} | By JWRESEARCH | Category: Laboratory Glassware

A fractionating column is the part of a distillation train that does the separating. The flask supplies vapour and the condenser removes heat, but the column is where vapour and liquid meet often enough for a close-boiling mixture to resolve into usable cuts.

At JW RESEARCH SUPPLY, we supply borosilicate 3.3 fractionating columns to chemistry, pharmaceutical, flavour and fragrance, petrochemical and teaching laboratories across Singapore. This guide covers column types, the numbers that predict performance, and the operating points that decide whether a column delivers its rated plate count.

Column Types

A Vigreux column uses inward-pointing indentations that force vapour to change direction and give liquid a surface to run down. There is no packing to channel or replace, cleaning is simple, and the same column behaves the same way run after run — the default for teaching and for samples that crystallise or leave residue.

A packed column holds glass helices, Raschig rings or structured packing in a straight tube. Packing gives more surface per unit length and therefore more plates, at the cost of hold-up volume, longer equilibration and a component that can foul or need repacking.

Column Type	Typical Length	Plates per 20 cm	Hold-up	Best For
Vigreux, plain	200 – 600 mm	0.5 – 1.5	Low to medium	General fractionation, teaching, dirty samples
Vigreux, vacuum jacketed	300 – 600 mm	0.8 – 1.8	Low to medium	High-boiling or vacuum work needing insulation
Packed, glass helices	300 – 600 mm	2 – 4	Medium	Close-boiling clean mixtures
Packed, structured	300 – 500 mm	4 – 8	Low per plate	High-efficiency laboratory and pilot work
Spinning band	300 – 600 mm	10 – 30	Very low	Small samples needing very high resolution

Specification Reference

Parameter	Typical Value	What It Affects
Material	Borosilicate glass 3.3	Thermal shock resistance and chemical durability
Internal diameter	10, 15, 20, 25, 30 mm	Throughput against resolution; narrow is sharper
Effective length	200, 300, 400, 600 mm	Plate count at a given HETP
Joint sizes	14/20, 24/40, 29/32	Compatibility with flask, head and condenser
Colour band	Clear, amber, black	Light-sensitive compounds, visible band tracking
Jacket	Vacuum, silvered or unsilvered	Heat loss along the column and reflux stability
Packing options	Glass helices, Raschig rings, structured mesh	Surface area, hold-up and pressure drop
Max working temperature	Up to 200 °C at the column wall	Thermal stress and joint grease choice

Reading HETP and Plate Count

Performance is quoted as HETP — height equivalent to a theoretical plate — in millimetres. Divide effective length by HETP to get the plate count: a 400 mm column with a 100 mm HETP is a four-plate column. HETP is quoted at a stated boil-up rate and pressure, so compare columns with it rather than treating it as a guarantee.

Three things limit the real plate count. Push boil-up too high and the column floods, liquid accumulates and separation collapses. Leave the column uninsulated and reflux condenses on the wall above the packing, destabilising the band. Carry too much hold-up and the first fraction is diluted by the previous cut, which is why narrow columns suit small samples.

Matching Column to Head and Condenser

Use a still head with a reflux splitter so the reflux ratio is controlled rather than accidental, and size the condenser for the total vapour load — distillate plus returned reflux. A condenser sized only for take-off will pass vapour to the pump once reflux is turned up. Keep one joint size through the train, normally 24/40 or 29/32; every adapter adds a leak path and a pocket of hold-up.

Operating a Fractional Distillation

Charge the flask to no more than two thirds, add boiling chips or a stir bar, and bring the column to total reflux before taking anything off. Set the reflux ratio once the head temperature stabilises: 2:1 to 5:1 for close-boiling pairs, 1:1 for easy separations, held constant through the cut.

Watch the head temperature rather than the flask temperature. A steady head temperature means one component is arriving; a slow climb means the cut is running out or the column is over-driven. Record head temperature, pressure and reflux ratio with each fraction so the run can be repeated.

Vacuum Fractionation

Under vacuum, use a vacuum-jacketed or silvered column so the wall stays hot and reflux does not condense above the packing. Reduce pressure slowly with a bleed valve, keep a cold trap before the pump, and check that the head thermometer reads as expected for the reduced pressure.

Selection Checklist

Set the plate count you need from the boiling-point gap before choosing length.
Choose the narrowest diameter that still handles your sample volume.
Pick Vigreux for dirty or crystallising samples, packed for clean close-boiling duties.
Specify vacuum jacketing when the pot temperature exceeds about 150 °C.
Order a reflux splitter head and match the condenser to reflux plus take-off.

Cleaning and Storage

Rinse with carrier solvent while the column is still warm, then detergent and water, and dry by drawing air through it. Empty and repack packed columns that show channelling or trapped residue, and store columns vertically on a padded rack; a chipped joint makes the column unusable.

Frequently Asked Questions

How many plates does a Vigreux column give?
About 0.5 to 1.5 per 20 cm, so a 60 cm column is worth roughly three to five plates.

Can a Vigreux column be used under vacuum?
Yes, but specify a vacuum-jacketed or silvered version so reflux does not condense above the packing.

How do I know the column is flooding?
Liquid accumulates in the packing, pressure drop rises and the head temperature becomes unsteady. Reduce the mantle setting and let it drain.

Does JWRESEARCH supply fractionating columns in Singapore?
Yes — Vigreux, vacuum-jacketed and packed columns with matching heads and condensers, delivered across Singapore.

Contact JWRESEARCH

JW RESEARCH SUPPLY — laboratory equipment and consumables, Singapore.
Telephone / WhatsApp: +65 8039 3660
Email: SINGAPORE@JWSHY.COM
Website: www.jwresearch.cn