Paraffin wax
Paraffin wax
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Paraffin wax

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Paraffin wax

Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and begins to melt above approximately 37 °C (99 °F), and its boiling point is above 370 °C (698 °F). Common applications for paraffin wax include lubrication, electrical insulation, and candles; dyed paraffin wax can be made into crayons.

Un-dyed, unscented paraffin candles are odorless and bluish-white. Paraffin wax was first created by Carl Reichenbach in Germany in 1830 and marked a major advancement in candlemaking technology, as it burned more cleanly and reliably than tallow candles and was cheaper to produce.

In chemistry, paraffin is used synonymously with alkane, indicating hydrocarbons with the general formula CnH2n+2. The name is derived from Latin parum ("very little") + affinis, meaning "lacking affinity" or "lacking reactivity", referring to paraffin's unreactive nature.

Paraffin wax is mostly found as a white, odorless, flavourless, waxy solid, with a typical melting point between about 46 and 68 °C (115 and 154 °F), and a density of around 900 kg/m3. It is insoluble in water, but soluble in ether, benzene, and certain esters. Paraffin is unaffected by most common chemical reagents but burns readily. Its heat of combustion is 42 MJ/kg.

Paraffin wax is an excellent electrical insulator, with a resistivity of between 1013 and 1017 ohm-metre. This is better than nearly all other materials except some plastics (notably PTFE). It is an effective neutron moderator and was used in James Chadwick's 1932 experiments to identify the neutron.

Paraffin wax is an excellent material for storing heat, with a specific heat capacity of 2.14–2.9 J⋅g−1⋅K−1 (joules per gram per kelvin) and a heat of fusion of 200–220 J⋅g−1. Paraffin wax phase-change cooling coupled with retractable radiators was used to cool the electronics of the Lunar Roving Vehicle during the crewed missions to the Moon in the early 1970s. Wax expands considerably when it melts and so is used in wax element thermostats for industrial, domestic and, particularly, automobile purposes.

If pure paraffin wax is heated in a partially open glass vessel until it nears the flash point and then rapidly cooled, its vapors may autoignite as result of reaching boiling liquid pressure.

Paraffin wax was first created in 1830 by German chemist Karl von Reichenbach when he attempted to develop a method to efficiently separate and refine waxy substances naturally occurring in petroleum. Paraffin represented a major advance in the candle-making industry because it burned cleanly and was cheaper to manufacture than other candle fuels such as beeswax and tallow. Paraffin wax initially suffered from a low melting point. This was remedied by adding stearic acid. The production of paraffin wax enjoyed a boom in the early 20th century due to the growth of the oil and meatpacking industries, which created paraffin and stearic acid as byproducts.

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