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Paraffin wax

physical science Maturity 5-7 Next article →

Paraffin wax is a soft, colorless solid derived from petroleum, coal, or oil shale. It is composed of a mixture of hydrocarbon molecules. These molecules contain between 20 and 40 carbon atoms. In chemistry, paraffin is often used interchangeably with the term alkane. An alkane is a type of hydrocarbon with the general formula CnH2n+2.

Hentriacontane
Hentriacontane

The name itself comes from Latin roots. The words "parum" and "affinis" mean "very little" and "lacking affinity." This refers to the unreactive nature of the substance. Because it is unreactive, it does not easily change when it touches most common chemicals.

To understand how paraffin is made, we must look at the manufacturing process. The starting material is called slack wax. This is a byproduct of refining lubricating oil. Slack wax is a mixture of both oil and wax. The first goal is to remove the oil through a process called de-oiling or de-waxing. This is achieved through crystallization. Workers heat the slack wax and mix it with a solvent, such as a ketone.

Bicycle chain in paraffin wax just about to solidify
Bicycle chain in paraffin wax just about to solidify

As the mixture cools, the wax crystallizes out of the solution. The mixture is then filtered into two separate streams. One stream is a solid containing wax and some solvent. The other is a liquid consisting of oil and solvent. After the solvent is recovered through distillation, the result is called product wax. This wax can be further processed to remove odors or colors. It can also be blended to reach a specific melting point.

Paraffin wax possesses several unique physical properties. It is a white, odorless, and tasteless waxy solid. It typically has a melting point between 46 and 68 degrees Celsius. This melting point can change based on oil content and crystalline structure. The density of the wax is approximately 900 kg/m3. While it is insoluble in water, it can dissolve in benzene or ether. One of its most important traits is its high heat of combustion. This value is 42 MJ/kg, meaning it releases significant energy when burned.

Candle black
Candle black

It also expands considerably when it transitions from a solid to a liquid. Because of this expansion, it is used in wax element thermostats for automobiles and industrial tools.

The history of paraffin is tied to a major shift in technology. A German chemist named Carl Reichenbach first created paraffin in 1830. He was attempting to find better ways to refine waxy substances from petroleum. His work revolutionized the candle-making industry. Before this, people relied on tallow or beeswax for light. Paraffin was much cheaper to produce than those alternatives. It also burned more reliably and cleanly. In the early 20th century, the production of paraffin saw a massive boom. This was due to the growth of the meatpacking and oil industries. Both industries produced paraffin and stearic acid as byproducts. Adding stearic acid helped solve the problem of paraffin having a low melting point.

Beyond simple candles, paraffin serves many technical roles. It is an excellent electrical insulator. Its resistivity ranges between 10^13 and 10^17 ohm-metre. This makes it more effective at blocking electricity than almost any other material, except for certain plastics like PTFE. It is also an effective neutron moderator. This property was vital in 1932 when James Chadwick used it to identify the neutron.

Hentriacontane
Hentriacontane

In laboratories, scientists use paraffin for histology. They impregnate tissue samples with the wax to allow for very thin slicing. This helps researchers study the tiny details of biological cells.

Paraffin is also used for thermal management in extreme environments. It is a great material for storing heat due to its specific heat capacity. It has a heat of fusion between 200 and 220 J⋅g−1. This means it can absorb and release energy as it changes state. During the early 1970s, this was used on the Moon. The Lunar Roving Vehicle used paraffin-based cooling to protect its electronics. This helped manage the heat during crewed missions. Even modern spacecraft, like the MESSENGER mission to Mercury, have used such materials to handle excessive heat.

Today, you can find paraffin in many everyday items. It is used to make colorful crayons and various types of wax for skis or surfboards. In the food industry, food-grade paraffin is used as a shiny coating for candy. It is also used to coat hard cheeses like Edam. Some people even use it as a lubricant for bicycle chains.

Bicycle chain in paraffin wax just about to solidify
Bicycle chain in paraffin wax just about to solidify

It is even used in forensic science. A nitrate test uses paraffin wax to detect specific chemicals on a suspect's hands. From space exploration to household tools, this simple hydrocarbon plays a massive role in our world.

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File:Candle black.jpg
Candle black.jpg
File:Hentriacontane.svg
Hentriacontane.svg
File:Bicycle chain in paraffin wax just about to solidify.jpg
Bicycle chain in paraffin wax just about...
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