Paraffin is the common name for the family of saturated hydrocarbons that chemists call alkanes, and in trade it usually means paraffin wax: a soft, colourless or white solid obtained from petroleum. Paraffin wax is a mixture of hydrocarbon molecules with between 20 and 40 carbon atoms, and it typically melts between 46 and 68°C. In British usage "paraffin" can also mean kerosene, the liquid fuel, which is a different product.
What is paraffin?
The word covers three things, and an enquiry should say which is meant.
- Paraffin wax. The solid wax used in candles, packaging and many industrial products. This is the subject of this guide.
- Paraffin (kerosene). In the UK, South Africa and several other countries, "paraffin" is the everyday name for kerosene, a thin liquid fuel for heaters, lamps and stoves. Its molecules are much shorter than those of the wax, mostly 9 to 16 carbon atoms. See kerosene.
- Liquid paraffin. A highly refined mineral oil used in pharmaceuticals and cosmetics, known in the US as mineral oil. See white mineral oil.
In chemistry, "paraffin" is simply a synonym for alkane, whatever the chain length. The three products above are all paraffins in that sense. They differ in how long the carbon chains are, and so in whether the material is a thin liquid, an oil or a solid.
What is the chemical formula of paraffin wax?
Paraffin wax has no single formula, because it is a mixture. Its molecules follow the general formula of the alkanes:
CnH2n+2
where n is the number of carbon atoms. For paraffin wax, n runs from about 20 to 40.
The paraffin formula, worked through
Put the two ends of the range into the general formula:
- n = 20 gives C20H42.
- n = 40 gives C40H82.
A typical component in the middle of the range is hentriacontane, C31H64. A commercial wax contains many such molecules. Most are straight chains, called normal paraffins, and the rest are branched or ring-containing molecules. The share of straight chains, and the spread of chain lengths, set the melting point and the hardness.
The CAS number used for paraffin wax on safety data sheets is 8002-74-2.
Physical properties
| Property | Typical value |
|---|---|
| Appearance | Colourless to white solid, translucent, odourless |
| Carbon range | About C20 to C40 |
| Melting point | Typically 46 to 68°C, varying with oil content and crystal structure |
| Density | About 900 kg/m³ |
| Flash point | 200 to 240°C |
| Boiling point | Above 370°C |
| Solubility in water | Insoluble |
Paraffin wax is a good electrical insulator and stores a useful amount of heat as it melts, which is why it also appears in insulation and heat-storage applications.
How is paraffin wax made?
Paraffin wax is a by-product of making lubricating base oil. A base oil must stay liquid in the cold, so the refinery has to take the wax out of it.
- Distillation. Crude oil is distilled, and the heavier cuts from the vacuum column become lube oil feedstock.
- Solvent extraction. A solvent removes aromatic and polar molecules from the feedstock.
- Solvent dewaxing. The oil is mixed with a solvent and chilled. The wax crystallises and is filtered out. The oil carries on to become base oil. The filtered wax, still holding a good deal of oil, is called slack wax.
- De-oiling. The slack wax is warmed, mixed with a solvent such as a ketone, and cooled again so that the wax crystallises and the oil stays in solution. Distilling off the solvent leaves the product wax on one side and an oily by-product, foots oil, on the other.
- Finishing. Fully refined grades are then hydrofinished, treated with hydrogen over a catalyst, to improve colour, odour and stability.
The German chemist Carl Reichenbach first produced paraffin wax in 1830.
What are the grades of paraffin wax?
Petroleum waxes are graded first by how much oil is left in them. The lower the oil content, the more refined the wax, the whiter and harder it is, and the higher its value. ExxonMobil, one of the large producers, describes the three steps this way:
| Grade | Oil content (ExxonMobil definitions) | Character |
|---|---|---|
| Fully refined wax | Less than 1% | Hard, highly crystalline, usually white |
| Scale wax (semi refined) | Typically 1 to 4% | Partially refined, yellow to white |
| Slack wax | Usually above 4% | Softer, usually yellow; the feedstock for the other two |
These thresholds are not universal. Producers and national standards draw the lines in different places, and individual fully refined grades are sold to tighter limits. One ExxonMobil fully refined grade, for example, is specified at 0.5% oil by weight, measured by ASTM D721, with a melting point of 55.6 to 57.2°C by ASTM D87. A contract should therefore state the oil content as a number with its test method, and not rely on the words "fully refined" or "semi refined".
The second grading number is the melting point. Fully refined waxes are offered across a range of melting points; ExxonMobil's fully refined range runs from 51 to 73°C. Trade grades are usually named by their melting band in degrees Celsius.
A buyer's sheet will normally also carry colour on the Saybolt scale and needle penetration, a measure of hardness.
The product pages for each grade are fully refined paraffin wax, semi refined paraffin wax and slack wax.
Paraffin wax and microcrystalline wax
The heaviest wax stream in a refinery comes from deasphalted vacuum residue, the same stream that yields bright stock base oil. Its molecules are larger and mostly branched, the crystals are much finer, and the melting point is higher. This is the raw material for microcrystalline wax, which is more flexible and tacky than paraffin wax. See microcrystalline wax and petrolatum.
What is paraffin wax used for?
- Candles. The largest and best-known use. Pillar and taper candles need a harder, higher-melting wax, and container candles use a softer, lower-melting one.
- Packaging. Coatings for paper, board and food wraps, where the wax acts as a moisture barrier.
- Rubber and tyres. Wax migrates to the surface of rubber and protects it from ozone cracking.
- Food uses. Food-grade paraffin, E905 in the European numbering, is used in coatings and chewing gum base where the producer certifies the grade.
- Other uses. Crayons, polishes, matches, lubrication, electrical insulation, cosmetics and hot-melt adhesives.
Oil content matters differently in each. Too much oil in a candle or a coating shows up as surface bleed, tackiness and odour, which is why those buyers specify fully refined grades. Slack wax goes into uses where colour and oil are less critical, and into further refining.
How paraffin wax is traded
Paraffin wax is sold per tonne on a named melting point and oil content, in slabs packed in cartons or bags, or as pastilles and granules in bags, loaded in dry containers. Packing for slack wax is agreed lot by lot. Terms are normally FOB, CFR or CIF.
The certificate of analysis should show melting point, oil content, colour and penetration, each with its test method, and should name the producing refinery and the lot.
CBIL is a commodity brokerage company. We broker paraffin wax between a named refinery or seller and a named buyer, against independent inspection by SGS, Intertek or a similar company at loading. The grades are listed on our paraffin wax page.
Request a paraffin wax quote with the melting point, oil content, form, quantity and destination port.