A candle (C25H52) is a solid block of wax with an embedded wick, which is lit to provide light, and sometimes heat, and historically as a method of keeping time. Candles have appeared as a source of fine and ultrafine particles in indoor air (e.g. Hussein et al. 2006). Fine et al. (1999), found high Organic Carbon (OC) emissions connected to the extinction of the candle and high EC concentrations when the flame was burning unsteady.
In the mid 1800s there were two major developments in the candle wax industry, stearin wax and paraffin wax. Stearin wax was developed from stearic acid extracted from the fatty acids of animals. This type of candle wax became popular in Europe. Paraffin wax, which became popular in the United States, was developed as a result of removing the natural waxy substance formed during the process of refining petroleum, or crude oil. During the next 150 years many further developments of candle wax took place. These developments include synthetic candle waxes , chemically synthesized candle waxes, gel wax, vegetable based candle waxes, candle wax blends and custom candle wax formulas. The most popular type of candle wax used today is paraffin wax. The chemical composition of paraffin wax is commonly referred to as C25H52 (carbon and hydrogen). However, the actual number of carbon atoms can typically range form 22 to 27. Paraffin has been employed for the manufacture of candles since the 19th century. A mixture of hydrocarbons, it is now obtained almost exclusively from petroleum . the melting point of paraffin varies with the chain lengths of its constituents. Pure paraffins are colorless and transparent, and display a wide range of softening points. (http://candles.lovetoknow.com/What_Is_the_Chemical_Composition_of_Candle_Wax)
Candles can also be made from beeswax, soy, other plant waxes, and tallow (a by-product of beef-fat rendering). Gel candles are made from a mixture of paraffin and plastic. A candle manufacturer is traditionally known as a chandler. Various devices have been invented to hold candles, from simple tabletop candle holders, to elaborate chandeliers. Before the invention of electric lighting candles and oil lamps were commonly used for illumination. In areas without electricity, they are still used routinely. Until the 20th century, candles were more common in northern Europe. In southern Europe and the Mediterranean, oil lamps predominated. In the developed world today, candles are used mainly for their aesthetic value and scent, particularly to set a soft, warm, or romantic ambiance, and for emergency lighting during electrical power failures. Scented candles are used in aromatherapy. They are also used for religious or ritual purposes. (http://scilifestyle.com/all-uses-of-candles.html)
For a candle to burn, a heat source, commonly a naked flame is used to light the candles wick which melts and vaporizes a small amount of fuel, the wax. Once vaporized, the fuel combines with oxygen in the atmosphere to form a flame. This flame provides sufficient heat to keep the candle burning via a self-sustaining chain of events: the heat of the flame melts the top of the mass of solid fuel, the liquefied fuel then moves upward through the wick via capillary action, and the liquefied fuel is then vaporized to burn within the candle's flame.
The burning of the fuel occurs in several distinct regions (as evidenced by the various colors that can be seen within the candle's flame). Within the blue regions, hydrogen is being separated from the fuel and burned to form water vapor. The brighter, yellow part of the flame is the remaining carbon being oxidized to form carbon dioxide.
As the mass of solid fuel is melted and consumed, the candle grows shorter. Portions of the wick that are not emitting vaporized fuel are consumed in the flame. The incineration of the wick limits the exposed length of the wick, thus maintaining a constant burning temperature and...
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