Lecture I - A Candle: Sources of the Flame
Contents of this webpage
Outline of Faraday's Chemical History of the Candle, Lecture I
Because Faraday's style is sometimes hard to follow (we can't see what he was actually doing during the lecture, and he sometimes rambles), I've put together a brief outline of the topics and demonstrations he uses for each lecture. Here's the first one. Notice that although Faraday seems to move almost randomly through topics, when we look at his lecture more carefully, we realize that he has organized this one around the properties of the material in the candle, and the different states (solid, liquid, gas) which it assumes as it burns.
- Why studying a candle is interesting
- The composition of different kinds of candles
- Candlewood (Irish bogwood)
- Dips or tapers
- Tallow or suet candles
- Sperm candles
- How candles are made
- Molded candles
- Dipped candles
- Some basic observations of the solid candle material
- Formation of the cup
- Guttering and candle flicker
- Shape of air currents around candle
- Observations on the liquid (melted) material
- Capillary action draws liquid up wick to burn
- Capillary action in other materials
- Salt pillar
- Cloth in basin
- Observations on the vaporous material
- The shape of a flame
- Hooker's observations of candle flame
- Dark areas in the flame
- Bright areas in the flame
- Air currents around the flame
- Using sunlight to look at a flame's shadow
- Changing the direction of the flame (using burning alcohol)
- The many changing shapes of a large source of flame
Reading notes (in the general order in which the terms or concepts appear)
Remember, we don't have any tests for this summer course--the terms I list here are just to help you with the reading, so don't spend a lot of time memorizing these! Faraday sometimes uses words which have changed meaning, or mentions items which we no longer use. I hope this list helps you understand his lecture a little better. If I missed a term and you need the definition, let me know, so that I can add it to the list.
- Candle making dates back to about 3000 BC (based on the use of candlesticks in Crete and Egypt). Until the invention of electrical and gas lights, candles provided most of the light necessary for performing indoor tasks. Candles were also marked according to the length of time necessary for them to burn, and used as simple time-keeping devices.
- bogwood or candlewood:
- Wood preserved in a peat bog, and permeated with decayed organic material that will burn easily.
- Candles made by successively dipping the wick in liquid wax
- Davy lamp:
- A safetly lamp in which the flame was surrounded by metal gauze. The metal also helped lead heat away from the flame, keeping the whole lamp cooler. The Davy lamp safer to use in mines, where the hot flame of other types of lamps could ignite coal gas and cause explosions.
- Russian tallow:
- A material which comes from boiling animal fat in lye or lime.
- Gay Lussac:
- French chemist and physicist Joseph-Louis Gay-Lussac (1778-1850), a pioneering investigator of the behavior of gases and various techniques of chemical analysis, and one of Faraday's contemporaries.
- Similar to sterno, a type of slow-burnging fuel now used for heating food trays. Stearic acid is made by separating fatty acids from glycerins in animal fat. Modern candles are usually a mixture of parafin and stearic acid.
- A waxy substance from the head of the sperm whale. It was used for making candles and cosmetics.
- A substance composed primarily of hydrocarbons (hydrogen-carbon compounds) which comes from petroleum.
- Also called lime: the compound calcium oxide (calcium and oxygen).
- Sometimes spelled camphene. This is a crystalline compound used to make synthetic camphor, a substance used in mothballs.
- I'm not certain who this is.
- voltaic battery:
- The early electrical cell made by Volta, which used wafers of copper and zinc separated by cloth soaked in acid. Sir Humphrey Davy, Faraday's patron at the Royal Institute, created an enormous voltaic battery which he and Farady used as a source of electric current for many of their experiments. Apparently, Faraday had one set up for the demonstrations he made during his lectures.
- spirit or spirit-of-wine:
- Another term for alcohol. Modern chemistry sets sometimes include alcohol lamps which use isopropyl alcohol as a fuel source.
- From Faraday's description, this is similar to a flaming-pudding dessert. Raisins are placed in a dish of warm brandy, which is ignited. The heat causes the raisins to plump up and skitter about, but the alcohol in the brandy burns out before the raisins burn up, leaving the plum raisins in a sweet, sticky syrup. Faraday notes that the dish and brandy are like the solid candle and melted candlewax, and the raisins are like the wick, so putting several raisins into the brandy will cause several flames to burn at the same time in different parts of the bowl.
- Ask questions about any part of the lecture you like!
- What is the difference between a physical change (from solid to liquid, for example), and a chemical change? Why is each physical state necessary for the candle to burn?
- Why do scientists and philosophers look for the causes of events and things?
- What is capillary action? Why is it important for the burning candle?
- What is combustion?
- For more information on candlemaking, check out Sharon Parmelia's Candlemaking page.
- Candlecraft is the web site of a professional candle-making group.
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