Paraffin wax

Paraffin wax (or petroleum wax) is a soft colorless solid, derived from petroleum, coal or shale oil, that consists of a mixture of hydrocarbon molecules containing between twenty and forty carbon atoms. It is solid at room temperature and begins to melt above approximately 37 °C (99 °F), its boiling point is >370 °C (698 °F). Common applications for paraffin wax include lubrication, electrical insulation, and candles; dyed paraffin wax can be made into crayons. It is distinct from kerosene and other petroleum products that are sometimes called paraffin. 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 ('barely') + affinis, meaning 'lacking affinity' or 'lacking reactivity', referring to paraffin's unreactive nature. Paraffin wax is mostly found as a white, odorless, tasteless, 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 Teflon). 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 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 manned missions to the Moon in the early 1970s. Wax expands considerably when it melts and this allows its use in wax element thermostats for industrial, domestic and, particularly, automobile purposes. Paraffin wax was first created in 1830 by the German chemist Karl von Reichenbach when he tried to develop the means to efficiently separate and refine the waxy substances naturally occurring in petroleum. Paraffin represented a major advance in the candlemaking industry, because it burned more cleanly and reliably, and was cheaper to manufacture than any other candle fuel. Paraffin wax initially suffered from a low melting point; however, this shortcoming was later remedied by the addition of harder stearic acid. The production of paraffin wax enjoyed a boom in the early 20th century as a result of the growth of the meatpacking and oil industries, which created paraffin and stearic acid as byproducts. The feedstock for paraffin is slack wax, which is a mixture of oil and wax, a byproduct from the refining of lubricating oil.