The Chemical History of a Candle

Source-grounded summary

What the book is about

Michael Faraday’s The Chemical History of a Candle is a series of engaging lectures that explore the science behind a candle’s flame, transforming a familiar object into a gateway to understanding chemistry and natural philosophy. Faraday begins by describing various types of candles—made from tallow, beeswax, spermaceti, paraffin, and even Japanese wax—and explains how they are made through dipping, mould casting, or coating. He then carefully examines the structure of the candle flame, showing how melted wax is drawn up the wick by capillary attraction and vaporizes to sustain combustion. Through simple yet vivid experiments, he reveals how air currents shape the flame and how the flame’s brightness depends on tiny solid particles of carbon glowing within it.

Faraday distinguishes different kinds of combustion, demonstrating that bright flames owe their light to solid particles glowing, while flames burning pure gases like hydrogen can be hot but dim. He uses experiments with phosphorus, gunpowder, and iron filings to illustrate these principles, emphasizing the interplay of fuel, air, heat, and light. The production of water from combustion surprises many readers; Faraday shows that burning hydrogen in oxygen produces water identical to natural water, and he explores water’s physical states—ice, liquid, and steam—highlighting their volume changes and effects, such as ice expanding enough to break iron bottles.

Moving beyond the candle, Faraday explores gases involved in combustion and air’s composition. He produces hydrogen gas by reacting zinc with acid and demonstrates its lightness and combustibility. He prepares oxygen and shows its role in supporting intense combustion, while nitrogen is identified as inert and non-supportive of flame. Atmospheric air is revealed as a mixture of about 20% oxygen and 80% nitrogen by volume. Faraday also investigates atmospheric pressure and elasticity through hands-on experiments like suction cups and water retention in inverted glasses.

Further lectures focus on carbonic acid gas (carbon dioxide), produced by candle combustion and respiration. Faraday demonstrates its properties: it is heavier than air, non-combustible, and reacts with lime-water to form carbonate of lime. He draws a compelling analogy between candle combustion and animal respiration, showing that breathing consumes oxygen and produces carbonic acid, linking chemical processes in living beings to those in flames. This connection underscores the interdependence of animals and plants through chemical exchanges.

The final parts of the lectures delve into metals, especially platinum. Faraday describes its properties, occurrence, and refining processes, including Deville’s method involving intense heat and volatilization of impurities. He demonstrates welding platinum wire and discusses how lead can damage platinum by chemical affinity. Experiments with metal vapors and electric discharges illustrate the volatility and characteristic light emissions of metals like mercury, lead, gold, and silver.

Throughout, Faraday speaks with enthusiasm and care, addressing his audience as 'my boys and girls' and encouraging curiosity, careful observation, and philosophical questioning. He balances scientific rigor with accessible explanations, vivid demonstrations, and occasional humor. Footnotes provide detailed chemical and physical background, while the author’s reflective remarks reveal his affection for the subject and his audience. Though some experimental details and conclusions extend beyond the supplied text, the lectures collectively illuminate the chemistry behind a candle’s flame and its broader connections to natural phenomena.