Paraffin wax

Paraffin wax is the name given to a form of wax that is either refined from petroleum products or synthesized from coal products. It has a low melting temperature and softens easily. This allows it to be produced in a variety of forms, from liquids to small beads to larger sheets and blocks. Depending on the form, it ranges in color from clear to white but translucent. Paraffin wax is flammable and can burn; this makes it useful in candle making and some lamp oils. It is also used in wax paper, many inks, lubricants, sealants, rust preventatives, and waterproofing. Paraffin wax is also used in food products and has some medical uses as well.

Background

The word paraffin comes from the Latin words parum, which means "barely" and affinis, which means "lacking affinity." In its original form, paraffin is an organic hydrocarbon mixture that is classified as an alkene. Paraffin, like all alkenes, is very unreactive and lacks affinity for other substances; this led to its name. Wax is the name scientists give to organic compounds with low melting temperatures that make them easily moldable and that are hydrophobic, or resist water. The word wax comes from the Old English word weax, which referred to the substance made by bees known as beeswax.

In the early half of the nineteenth century, scientists learned to process petroleum in a way that released a waxy substance. A German chemist, Carl Reichenbach, who was researching uses for coal tar and its derivatives, discovered paraffin wax and the ways it could be useful in 1830. Over the next twenty years, other scientists refined paraffin and made it purer so that by the 1850s, it was replacing animal fats, such as whale oil and tallow, and beeswax in candle making. These products were time-consuming to procure and process and some gave off an odor when burned. Paraffin was easy to purchase and unscented. This made candles both cleaner burning and more affordable.

Medical practitioners also experimented with uses for paraffin. At various times in the 1800s, it was used as a way to replace removed spinal discs and injected as a way to stop muscle spasms. These uses were discontinued when it was found the wax easily migrated to other parts of the body and created a risk of embolisms, or obstruction of major blood vessels, as well as tissue damage. However, it was discovered that paraffin made a good medium for embedding tissue samples for microscopic study. Samples are treated to remove all fluids and then soaked in paraffin and dried; this makes them more stable and allows for thin slices of the tissue for study.

By the time of World War I (1914–1918), the medical field had discovered several additional uses for paraffin. Its low melting temperature meant that it could safely be applied to skin. French military doctors began using it as a cover for small open wounds, while the British took advantage of the fact that it becomes liquid at low temperatures to use as a therapeutic heat treatment for injured limbs. A large tub of paraffin was melted and the injured limb submerged, providing soothing heat to treat orthopedic injuries. Paraffin is still used in this way in the twenty-first century to treat some injuries as well as arthritis, bursitis, muscle and joint inflammation, fibromyalgia, and several skin conditions such as eczema, psoriasis, and dry flaky skin.

Overview

Paraffin wax is an odorless, colorless-to-white substance that is solid at room temperature but begins to soften and melt around 99 degrees Fahrenheit (37 degrees Celsius). This is just about the same as the standard body temperature for a healthy person; therefore, a small amount of paraffin held in the hand will begin to soften and melt, while just-melted paraffin feels comfortable on the skin. Like nearly any flammable substance, however, paraffin can be heated to temperatures that would burn human skin. It boils at 690 degrees Fahrenheit, or more than 370 degrees Celsius.

The wax is extracted from petroleum, coal, or shale. Petroleum-derived paraffin comes from slack oil, a by-product of the process of manufacturing lubricating oils. The slack oil is heated and mixed with a solvent, often ketone, and then cooled. This crystalizes the oil and helps separate it from the slack wax. The solvent is then removed by distillation, a process that alternates periods of heating and cooling to separate different substances. The resulting wax is then processed into either liquid or solid form and purified. It can also be mixed with other chemical additives based on its final use, such as hardeners or stabilizers. A similar process is used to extract wax from shale or coal by-products.

The resulting wax can then be used for a multitude of purposes. In some cases, such as candle making and the lost-wax casting process used to form objects of metal, paraffin replaces beeswax and other animal- and plant-based waxes. Additives are used to help the wax avoid breaking or chipping during the lost-wax process, which uses a shape carved in wax to form a mold. The wax is then melted and poured, leaving a cavity in the mold that can be filled with the desired metal. This technique is used for sculpture, jewelry making, and other forms of metalwork.

Paraffin is also used for a number of purposes in the food industry. Purified paraffin wax is considered safe to ingest in small amounts and is used as a binder in food items such as chewing gum and as a stabilizer in items such as chocolate. Small amounts of paraffin added to chocolate coatings help chocolate maintain its shape and shine. Wax is also applied to the outside of fresh fruit, where it also improves the shine and appeal while helping to seal in moisture and preserve freshness.

Paraffin is frequently used in cosmetics and health care aids. It holds color dyes well, making it useful for a large number of commercial products such as inks, colorants, polishes, paints, and crayons. It also appears in cleaning and polishing products, sealants, and building materials.

Although paraffin is widely used, some concerns have been raised about its safety. While it is odorless when burned, it does contain benzene, a known cancer-causing agent, which is released when it burns. The liquid form can also irritate skin and eyes.

Bibliography

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