["The Chemistry of a Candle," which Dickens and Leigh based upon a lecture by Michael Faraday at the Royal Institute, London, shows the novelist-editor both working with one of his underlings and popularizing the work of a pioneering scientist. Follow for a discussion of the novelist's complex roles as author and editor of Household Words. Philip V. Allingham, Contributing Editor, Victorian Web, transcribed the essay and translated it into HTML. GPL]

THE Wilkinsons were having a small party, — it consisted of themselves and Uncle Bagges—at which the younger members of the family, home for the holidays, had been just admitted to assist after dinner. Uncle Bagges was a gentleman from whom his affectionate relatives cherished expectations of a testamentary nature. Hence the greatest attention was paid by them to the wishes of Mr. Bagges, as well as to every observation which he might be pleased to make.

"Eh! what? you sir," said Mr. Bagges, facetiously addressing himself to his eldest nephew, Harry, — "Eh! what? I am glad to hear, sir, that you are doing well at school. Now — eh? now, are you clever enough to tell me where was Moses when he put the candle out?"

"That depends, uncle," answered the young gentleman, "on whether he had lighted the candle to see with at night, or by daylight, to seal a letter."

"Eh! Very good, now! 'Pon my word, very good," exclaimed Uncle Bagges. "You must be Lord Chancellor, sir — Lord Chancellor, one of these days."

"And now, uncle," asked Harry, who was a favourite with the old gentleman, "can you tell me what you do when you put a candle out?"

"Clap an extinguisher on it, you young rogue, to be sure."

"Oh! but I mean, you cut off its supply of oxygen," said Master Harry.

"Cut off its ox's — eh? What? I shall cut off your nose, you young dog, one of these fine days."

"He means something he heard at the Royal Institution," observed Mrs. Wilkinson. "He reads a great deal about chemistry, and he attended Professor Faraday's lectures there on the chemical history of a candle, and has been full of it ever since."

"Now, you sir," said Uncle Bagges, "come [439/440] you here to me, and tell me what you have to say about this chemical, eh?—or comical; which?— this comical chemical history of a candle." "He'll bore you, Bagges," said Mr. Wilkinson.

"Harry, don't be troublesome to your Uncle."

"Troublesome! Oh, not at all. He amuses me. I like to hear him. So let him teach his old uncle the comicality and chemicality of a farthing rushlight."

"A wax candle will be nicer and cleaner, uncle, and answer the same purpose. There's one on the mantel-shelf. Let me light it."

"Take care you don't burn your fingers, or set anything on fire," said Mrs. Wilkinson.

"Now, uncle," commenced Harry, having drawn his chair to the side of Mr. Bagges, "we have got our candle burning. What do you see?"

"Let me put on my spectacles," answered the uncle. "Look down on the top of the candle around the wick. See, it is a little cup full of melted wax. The heat of the flame has melted the wax just round the wick. The cold air keeps the outside of it hard, so as to make the rim of it. The melted wax in the little cup goes up through the wick to be burnt, just as oil does in the wick of a lamp. What do you think makes it go up, uncle?"

"Why — why, the flame draws it up, doesn't it?"

"Not exactly, uncle. It goes up through little tiny passages in the cotton wick, because very, very small channels, or pipes, or pores, have the power in themselves of sucking up liquids. What they do it by is called cap — something."

"Capillary attraction, Harry," suggested Mr. Wilkinson.

"Yes, that's it; just as a sponge sucks up water, or a bit of lump-sugar the little drop of tea or coffee left in the bottom of a cup. But I mustn't say much more about this, or else you will tell me I am doing something very much like teaching my grandmother to — you know what."

"Your grandmother, eh, young sharpshins?"

"No — I mean my uncle. Now, I'll blow the candle out, like Moses; not to be in the dark, though, but to see into what it is. Look at the smoke rising from the wick. I'll hold a bit of lighted paper in the smoke, so as not to touch the wick. But see, for all that the candle lights again. So this shows that the melted wax sucked up through the wick is turned into vapour; and the vapour burns. The heat of the burning vapour keeps on melting more wax, and that is sucked up too within the flame, and turned into vapour, and burnt, and so on till the wax is all used up, and the candle is gone. So the flame, uncle, you see, is the last of the candle, and the candle seems to go through the flame into nothing — although it doesn't, but goes into several things, and isn't it curious, as Professor Faraday said, that the candle should look so splendid and glorious in going away?"

"How well he remembers, doesn't he?" observed Mrs. Wilkinson.

"I dare say," proceeded Harry, "that the flame of the candle looks flat to you ; but if we were to put a lamp glass over it, so as to shelter it from the draught, you would see it is round, — round sideways, and running up to a peak. It is drawn up by the hot air; you know that hot air always rises, and that is the way smoke is taken up the chimney. What should you think was in the middle of the flame?"

"I should say, fire," replied Uncle Bagges.

"Oh, no! The flame is hollow. The bright flame we see is something no thicker than a thin peel, or skin; and it doesn't touch the wick. Inside of it is the vapour I told you of just now. If you put one end of a bent pipe into the middle of the flame, and let the other end of the pipe dip into a bottle, the vapour or gas from the candle will mix with the air there; and if you set fire to the mixture of gas from the candle and air in the bottle, it would go off with a bang."

"I wish you'd do that, Harry," said Master Tom, the younger brother of the juvenile lecturer.

"I want the proper things," answered Harry, "'Well, uncle, the flame of the candle is a little shining case, with gas in the inside of it, and air on the outside, so that the case of flame is between the air and the gas. The gas keeps going into the flame to burn, and when the candle burns properly, none of it ever passes out through the flame; and none of the air ever gets in through the flame to the gas. The greatest heat of the candle is in this skin, or peel, or case of flame."

"Case of flame!" repeated Mr. Bagges. "Live and learn. I should have thought a candle-flame was as thick as my poor old noddle."

"I can show you the contrary," said Harry. "I take this piece of white paper, look, and hold it a second or two down upon the candle-flame, keeping the flame very steady. Now I'll rub off the black of the smoke, and — there — you find that the paper is scorched in the shape of a ring ; but inside the ring it is only dirtied, and not singed at all."

"Seeing is believing," remarked the uncle.

"But," proceeded Harry, "there is more in the candle-flame than the gas that comes out of the candle. You know a candle won't burn without air. There must be always air around the gas, and touching it like, to make it burn. If a candle hasn't got enough air, it goes out, or burns badly, so that some of the vapour inside of the flame comes out through it in the form of smoke and this is the reason of a candle smoking. So now you know why a great clumsy dip smokes more than a neat wax candle; it is because the thick wick of the dip makes too much fuel in proportion to the air that can get to it." [440/441]

"Dear me! Well, I suppose there is a reason for everything," exclaimed the young philosopher's mamma.

"What should you say, now," continued Harry, "if I told you that the smoke that comes out of a candle is the very thing that makes a candle light? Yes; a candle shines by consuming its own smoke. The smoke of a candle is a cloud of small dust, and the little gains of the dust are bits of charcoal, or carbon, as chemists call it. They are made in the flame, and burnt in the flame, and, while burning, make the flame bright. They are burnt the moment they are made; but the flame goes on making more of them as fast as it burns them; and that is how it keeps bright. The place they are made in, is in the case of flame itself, where the strongest heat is. The great heat separates them from the gas which comes from the melted wax, and, as soon as they touch the air on the out-side of the thin case of flame, they burn."

"Can you tell how it is that the little bits of carbon cause the brightness of the flame?" asked Mr. Wilkinson.

"Because they are pieces of solid matter," answered Harry. "To make a flame shine, there must always be some solid — or at least liquidÑmatter in it."

"Very good," said Mr. Bagges, — " solid stuff necessary to brightness."

"Some gases and other things," resumed Harry, "that burn with a flame you can hardly see, burn splendidly when something solid is put into them. Oxygen and hydrogenÑtell me if I use too hard words, uncleÑoxygen and hydrogen gases, if mixed together and blown through a pipe, burn with plenty of heat but with very little light. But if their flame is blown upon a piece of quick-lime, it gets so bright as to be quite dazzling. Make the smoke of oil of turpentine pass through the same flame, and it gives the flame a beautiful brightness directly!"

"I wonder," observed Uncle Bagges, "what has made you such a bright youth."

"Taking after uncle, perhaps," retorted his nephew. "Don't put my candle and me out. Well, carbon or charcoal is what causes the brightness of all lamps, and candles, and other common lights; so, of course, there is carbon in what they are all made of."

"So carbon is smoke, eh? and light is owing to your carbon. Giving light out of smoke, eh? as they say in the classics," observed Mr. Bagges.

"But what becomes of the candle," pursued Harry," as it burns away? where does it go?"

"Nowhere," said his mamma, "I should think. It burns to nothing."

"Oh, dear, no!" said Harry, "everything—everybody goes somewhere."

"Eh!—rather an important consideration that," Mr. Bagges moralised.

"You can see it goes into smoke, which makes soot for one thing," pursued Harry. "There are other things it goes into, not to be seen by only looking, but you can get to see them by taking the right means, — just put your hand over the candle, uncle."

"Thank you, young gentleman, I had rather be excused."

"Not close enough down to burn you, uncle; higher up. There, — you feel a stream of hot air; so something seems to rise from the candle. Suppose you were to put a very long slender gas-burner over the flame, and let the flame burn just within the end of it, as if it were a chimney, — some of the hot steam would go up and come out at the top, but a sort of dew would be left behind in the glass chimney, if the chimney was cold enough when you put it on. There are ways of collecting this sort of dew, and when it is collected it turns out to be really water. I am not Joking, uncle. Water is one of the things which the candle turns into in burning, — water coming out of fire. A jet of oil gives above a pint of water in burning. In some lighthouses they burn, Professor Faraday says, up to two gallons of oil in a night, and if the windows are cold the steam from the oil clouds the inside of the windows, and, in frosty weather, freezes into ice."

"Water out of a candle, eh?" exclaimed Mr. Bagges. "As hard to get, I should have thought, as blood out of a post. Where does it come from?"

"Part from the wax, and part from the air, and yet not a drop of it comes either from the air or the wax. What do you make of that, uncle?"

"Eh? Oh! I'm no hand at riddles. Give it up."

"No riddle at all, uncle. The part that comes from the wax isn't water, and the part that comes from the air isn't water, but when put together they become water. Water is a mixture of two things, then. This can be shown. Put some iron wire or turnings into a gun-barrel open at both ends. Heat the middle of the barrel red-hot in a little furnace. Keep the heat up, and send the steam of boiling water through the red-hot gun-barrel. What will come out at the other end of the barrel won't be steam; it will be gas, which doesn't turn to water again when it gets cold, and which burns if you put a light to it. Take the turnings out of the gun-barrel, and you will find them changed to rust, and heavier than when they were put in. Part of the water is the gas that comes out of the barrel, the other part is what mixes with the iron turnings, and changes them to rust, and makes them heavier. You can fill a bladder with the gas that comes out of the gun-barrel, or you can pass bubbles of it up into a jar of water turned upside down in a trough, and, as I said, you can make this part of the water burn."

"Eh?" cried Mr. Bagges. "Upon my word! One of these days, we shall have you setting the Thames on fire."

"Nothing more easy," said Harry, "than [441/442] to burn part of the Thames, or of any other water; I mean the gas that I have just told you about, which is called hydrogen. In burning, hydrogen produces water again, like the flame of the candle. Indeed, hydrogen is that part of the water, formed by a candle burning, that comes from the wax. All things that have hydrogen in them produce water in burning, and the more there is in them the more they produce. When pure hydrogen burns, nothing comes from it but water, no smoke or soot at all. If you were to burn one ounce of it, the water you would get would be just nine ounces. There are many ways of making hydrogen, besides out of steam by the hot gun-barrel. I could show it you in a moment by pouring a little sulphuric acid mixed with water into a bottle upon a few zinc or steel filings, and putting a cork in the bottle with a little pipe through it, and setting fire to the gas that would come from the mouth of the pipe. We should find the flame very hot, but having scarcely any brightness. I should like you to see the curious qualities of hydrogen, particularly how light it is, so as to carry things up in the air; and I wish I had a small balloon to fill with it and make go up to the ceiling, or a bag-pipe full of it to blow soap-bubbles with, and, show how much faster they rise than common ones, blown with the breath."

"So do I," interposed Master Tom.

"And so," resumed Harry, "hydrogen, you know, uncle, is part of water, and just one-ninth part."

"As hydrogen is to water, so is a tailor to an ordinary individual, eh?" Mr. Bagges remarked.

"Well, now then, uncle, if hydrogen is the tailor's part of the water, what are the other eight parts? The iron turnings used to make hydrogen in the gun-barrel, and rusted, take just those eight parts from the water in the shape of steam, and are so much the heavier. Burn iron turnings in the air, and they make the same rust, and gain just the same in weight. So the other eight parts must be found in the air for one thing, and in the rusted iron turnings for another, and they must also be in the water; and now the question is, how to get at them?"

"Out of the water? Fish for them, I should say," suggested Mr. Bagges.

"Why, so we can," said Harry. "Only, instead of hooks and lines, we must use wires—two wires, one from one end, the other from the other, of a galvanic battery. Put the points of these wires into water, a little distance apart, and they instantly take the water to pieces. if they are of copper, or a metal that will rust easily, one of them begins to rust, and air-bubbles come up from the other. These bubbles are hydrogen. The other part of the water mixes with the end of the wire and makes rust. But if the wires are of gold, or a metal that does not rust easily, air-bubbles rise from the ends of both wires. Collect the bubbles from both wires in a tube, and fire them, and they turn to water again; and this water is exactly the same weight as 'the quantity that has been changed into the two gases. Now then, uncle, what should you think water was composed of?"

"Eh? well — I suppose of those very identical two gases, young gentleman."

"Right, uncle. Recollect that the gas from one of the wires was hydrogen, the one-ninth of water. What should you guess the gas from the other wire to be?"

"Stop — eh? — wait a bit — eh? — oh! — why, the other eight-ninths, to be sure."

"Good again, uncle. Now this gas that is eight-ninths of water is the gas called oxygen that I mentioned just now. This is a very curious gas. It won't burn in air at all itself, like gas from a lamp, but it has a wonderful power of making things burn that are lighted and put into it. If you fill a jar with it — "

"How do you manage that?" Mr. Bagges inquired.

"You fill the jar with water," answered Harry," and you stand it upside down in a vessel full of water too. Then you let bubbles of the gas up into the jar and they turn out water and take its place. Put a stopper in the neck of the jar, or hold a glass plate against the mouth of it, and you can take it out of the water and so have bottled oxygen. A lighted candle put into a jar of oxygen blazes up directly and is consumed before you can say Jack Robinson. Charcoal burns away in it as fast, with beautiful bright sparks — phosphorus with a light that dazzles you to look at — and a piece of iron or steel just made red-hot at the end first, is burnt in oxygen quicker than a stick would be in common air. The experiment of burning things in oxygen beats any fire-works."

"Oh how jolly!" exclaimed Tom.

"Now we see, uncle," Harry continued, "that water is hydrogen and oxygen united together, that water is got wherever hydrogen is burnt in common air, that a candle won't burn without air, and that when a candle burns there is hydrogen in it burning and forming water. Now, then, where does the hydrogen of the candle get the oxygen from, to turn into water with it?"

"From the air, eh?"

"Just so. I can't stop to tell you of the other things which there is oxygen in, and the many beautiful and amusing ways of getting it. But as there is oxygen in the air, and as oxygen makes things burn at such a rate, perhaps you wonder why air does not make things burn as fast as oxygen. The reason is, that there is something else in the air that mixes with the oxygen and weakens it."

"Makes a sort of gaseous grog of it, eh?" said Mr. Bagges. "But how is that proved?"

"Why, there is a gas, called nitrous gas, which, if you mix it with oxygen, takes all the [442/443] oxygen into itself, and the mixture of the nitrous gas and oxygen, if you put water with it, goes into the water. Mix nitrous gas and air together in a jar over water, and the nitrous gas takes away the oxygen, and then the water sucks up the mixed oxygen and nitrous gas, and that part of the air which weakens the oxygen is left behind. Burning phosphorus in confined air will also take all the oxygen from it, and there are other ways of doing the same thing. The portion of the air left behind is called nitrogen. You wouldn't know it from common air by the look; it has no colour, taste, nor smell, and it won't burn. But things won't burn in it, either; and anything on fire put into it goes out directly. It isn't fit to breathe, — and a mouse, or any animal, shut up in it, dies. It isn't poisonous, though; creatures only die in it for want of oxygen. We breathe it with oxygen, and then it does no harm, but good; for if we breathed pure oxygen, we should breathe away so violently, that we should soon breathe our life out. In the same way, if the air were nothing but oxygen, a candle would not last above a minute."

"What a tallow-chandler's bill we should have!" remarked Mrs. Wilkinson.

"'If a house were on fire in oxygen,' as Professor Faraday said, 'every iron bar, or rafter, or pillar, every nail and iron tool and the fire-place itself; all the zinc and copper roofs, and leaden coverings, and gutters, and pipes, would consume and burn, increasing the combustion."'

"That would be, indeed, burning 'like a house on fire,"' observed Mr. Bagges.

"'Think,"' said Harry, continuing his quotation, "'of the Houses of Parliament, or a steam-engine manufactory. Think of an iron-proof chest— no proof against oxygen. Think of a locomotive and its train,—every engine, every carriage, and even every rail would be set on fire and burnt up.' So now, uncle, I think you see what the use of nitrogen is, and especially how it prevents a candle from burning out too fast."

"Eh?" said Mr. Bagges. "Well, I will say I do think we are under considerable obliga-tions to nitrogen."

"I have explained to you, uncle," pursued Harry, "how a candle, in burning, turns into water. But it turns into something else besides that; there is a stream of hot air going up from it that won't condense into dew; some of that is the nitrogen of the air which the candle has taken all the oxygen from. But there is more in it than nitrogen. Hold a long glass tube over a candle, so that the stream of hot air from it may go up through the tube. Hold a jar over the end of the tube to collect some of the stream of hot air. Put some lime-water, which looks quite clear, into the jar; stop the jar, and shake it up. The lime-water, which was quite clear before, turns milky. Then there is something made by the burning of the candle that changes the colour of the lime-water. That is a gas, too, and you can collect it, and examine it. It is to be got from several things, and is a part of all chalk, marble, and the shells of eggs or of shell-fish. The easiest way to make it is by pouring muriatic or sulphuric acid on chalk or marble. The marble or chalk begins to hiss or bubble, and you can collect the bubbles in the same way that you can oxygen. The gas made by the candle in burning, and which also is got out of the chalk and marble, is called carbonic acid. It puts out a light in a moment; it kills any animal that breathes it, and it is really poisonous to breathe, because it destroys life even when mixed with a pretty large quantity of common air. The bubbles made by beer when it ferments, are carbonic acid, so is the air that fizzes out of soda-water,—and it is good to swallow though it is deadly to breathe. It is got from chalk by burning the chalk as well as by putting acid to it, and burning the carbonic acid out of chalk makes the chalk lime. This is why people are killed sometimes by getting in the way of the wind that blows from lime-kilns."

"Of which it is advisable carefully to keep to the windward," Mr. Wilkinson observed.

"The most curious thing about carbonic acid gas," proceeded Harry, "is its weight. Although it is only a sort of air, it is so heavy that you can pour it from one vessel into another. You may dip a cup of it and pour it down upon a candle, and it will put the candle out, which would astonish an ignorant person; because carbonic acid gas is as invisible as the air, and the candle seems to be put out by nothing. A sea-bubble of common air floats on it like wood water. Its weight is what makes it collect in brewers' vats and also in wells, where it is produced naturally; and owing to its collecting in such places it causes the deaths we so often hear about of those who go down into them without proper care. .It is found in many springs of water, more or less; and a great deal of it comes out of the earth in some places. Carbonic acid gas is what stupefies the dogs in the Grotto del Cane. Well, but how is carbonic acid gas made by the candle?"

"I hope with your candle you'll throw some light upon the subject," said Uncle Bagges.

"I hope so," answered Harry. "Recollect it is the burning of the smoke, or soot, or carbon of the candle that makes the candle-flame bright. Also that the candle won't burn without air. Likewise that it will not burn in nitrogen, or air that has been deprived of oxygen. So the carbon of the candle mingles with oxygen, in burning, to make carbonic acid gas, just as the hydrogen does to form water. Carbonic acid gas, then, is carbon or charcoal dissolved in oxygen. Here is black soot getting invisible and changing into air; and this seems strange, uncle, doesn't it?"

"Ahem! Strange, if true," answered Mr. [443/444] Bagges. "Eh? — well! I suppose it's all right."

"Quite so, uncle. Burn carbon or charcoal either in the air or in oxygen, and it is sure always to make carbonic acid, and nothing else, if it is dry. No dew or mist gathers in a cold glass jar if you burn dry charcoal in it. The charcoal goes entirely into carbonic acid gas, and leaves nothing behind but ashes, which are only earthy stuff that was in the charcoal, but not part of the charcoal itself. And now, shall I tell you something about carbon?"

"With all my heart," assented Mr. Bagges.

"I said that there was carbon or charcoal in all common lights,—so there is in every common kind of fuel. If you heat coal or wood away from the air, some gas comes away, and leaves behind coke from coal, and charcoal from wood; both carbon, though not pure. Heat carbon as much as you will in a close vessel, and it does not change in the least; but let the air get to it, and then it burns and flies off in carbonic acid gas. This makes carbon so convenient for fuel. But it is ornamental as well as useful, uncle. The diamond is nothing else than carbon." "The diamond, eh? You mean the black diamond."

"No; the diamond, really and truly. The diamond is only carbon in the shape of a crystal."

"Eh? and can't some of your clever chemists crystallise, a little bit of carbon, and make a Koh-i-noor?"

"Ah, uncle, perhaps we shall, some clay. In the meantime I suppose we must be content with making carbon so brilliant as it is in the flame of a candle. Well; now you see that a candle-flame is vapour burning, and the vapour, in burning, turns into water and carbonic acid gas. The oxygen of both the carbonic acid gas and the water comes from the air, and the hydrogen and carbon together are the vapour. They are distilled out of—the melted wax by the heat. But, you know, carbon alone can't be distilled by any heat. It can be distilled, though, when it is joined with hydrogen, as it is in the wax, and then the mixed hydrogen and carbon rise in gas of the same kind as the gas in the streets, and that also is distilled by heat from coal. So a candle is a little gas manufactory in itself, that burns the gas as fast as it makes it."

"Haven't you pretty nearly come to your candle's end?" said Mr. [Mrs.?] Wilkinson.

"Nearly. I only want to tell uncle, that the burning of a candle is almost exactly like our breathing. Breathing is consuming oxygen, only not so fast as burning. In breathing we throw out water in vapour and carbonic acid from our lungs, and take oxygen in. Oxygen is as necessary to support the life of the body, as it is to keep up the flame of a candle." "So," said Mr. Bagges," man is a candle, eh? And Shakespeare knew that, I suppose, (as he did most things,) when he wrote —

'Out, out, brief candle!'

Well, well; we old ones are moulds, and you young squires are dips and rushlights, eh? Any more to tell us about the candle?"

"I could tell you a great deal more about oxygen, and hydrogen, and carbon, and water, and breathing, that Professor Faraday said if I had time; but you should go and hear him yourself, uncle."

"Eh? well! I think I will. Some of us seniors may learn something from a juvenile lecture, at any rate, if given by a Faraday. And now, my boy, I will tell you what," added Mr. Bagges, "I am very glad to find you so fond of study and science; and you deserve to be encouraged: and so I'll give you a what-d' ye-call-it?—a Galvanic Battery on your next birth-day; and so much for your teaching your old uncle the chemistry of a candle."

Related Material

References

Leigh, Percival. "The Chemistry of a Candle."Household Words (3 August 1850): 439-444.


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Authors

Charles
Dickens

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Last modified 24 July 2023