metalresearcher
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Candles question
As far as I know, candles are usually paraffin (C31H64).
But sometimes I read about 'stearin' or 'palmitin' candles consisting of stearic acid C17H35COOH and palmitic acid C15H31COOH.
Is that true ?
And better candles don't soot much does that mean it is pure paraffin ?
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unionised
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Beeswax is another option.
You can make candles out of a number of materials.
Some may smoke less than others, but I'm pretty sure they will all smoke.
(well, apart from these)
https://www.amazon.co.uk/Battles-Sulphur-Candle-225g-Can/dp/...
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Dr.Bob
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Parafin is a complex mix of hydrocarbons, not just one compound. Much like gasoline contains many various hydrocarbons. And various organic acids
do make good candles, again, most animal derived fatty acids are a mixture of various length acids, almost all even numbers of carbons, but they peak
at C14, 16, and 18. The higher the percent of longer chains, the higher melting the candles. Some may be a mixture of several things, much like
table wine is often a mixture of several vintages. If you want pure materials, you will have to look carefully.
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highpower48
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Soy Wax is also used in modern candles.
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Melgar
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Candles are surprisingly complicated from a chemistry perspective. First, to add to what Dr. Bob said, animal fat also tends to contain protein,
specifically lipoproteins, which we know as cholesterol. Protein tends to smell bad when it burns, and produces a lot of smoke.
Paraffin isn't just any mix of hydrocarbons though, they have to all be saturated, which makes them very unreactive compared to other organic
compounds. (I believe their name came from a Greek or Latin phrase, something like "para affinis", meaning "next to no activity".)
Saturated hydrocarbons burn cleaner in a candle, because their single bonds can be broken by lower temperatures, meaning that they're less likely to
escape a candle flame as carbon particles (soot).* They be pyrolyzed with a carbon catalyst though, to make a flammable mix of gases. Cellulose
string, when burnt, forms a porous mass of carbon at the end that can catalyze this decomposition. It does this when you light a candle, with the
flame growing as it liquefies more and more wax. But eventually the catalytic tip is overwhelmed by molten wax and slows down, creating an
equilibrium.
So, why are some natural oils saturated and some unsaturated, anyway? It all comes down to what temperatures they experience, of all things. Birds
and mammals have high enough body temperatures to keep saturated fat from solidifying. Fish, on the other hand, do not. So their fat molecules have
kinks in them, in the form of carbon-carbon double bonds, to keep them liquid at cold temperatures. This goes for plants too. Most plants grown in
temperate climates have kinks in their fat molecules, to keep them from solidifying. But plants that grow only in tropical climates, like coconuts
and other palms, have saturated fat molecules that solidify when they get cold.
You might be wondering why soy candles are able to be solid at room temperature, even though soy grows in temperate climates. Well, that's because
soy candles are actually made from "trans fats", or "hydrogenated fats" like margarine and shortening are made from. These have had the kinks
chemically removed from their fat molecules, so they're solid at room temperature. This is supposed to be slightly bad for you if you spend your life
eating it, but there's certainly no harm in burning it in a candle.
You might also be thinking that you're going to correct me and tell me that saturated fats from natural sources aren't paraffins. This is true, but
because they're fatty acids (bonded to glycerol as triglycerides) they're also very resistant to chemical modification, since the only part that isn't
a straight-chain hydrocarbon is a carboxyl group, (technically an ester) which is very resistant to both oxidation and reduction.
* Double bonds can release more energy, but also require more activation energy.
[Edited on 9/17/17 by Melgar]
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