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Your textbook says a catalyst speeds up a reaction and is not used up. One of the first people to describe how that can happen was a woman in 1790s Britain whose birth name is not even known. Elizabeth Fulhame set out to dye cloth with real gold and ended up proposing a mechanism for catalysis. This post covers what she did, works her idea through in modern equations, and looks at what she got right and wrong.
Who was Elizabeth Fulhame?
Very little is known about her life. Physics Today's profile says historians suspect she was Scottish and met her husband, Thomas Fulhame, a medical student who took Joseph Black's chemistry classes at the University of Edinburgh. Her only known work is An Essay on Combustion, published in London in November 1794.
She explains how it began in the essay's preface, which you can read in a scanned 1794 copy: "The possibility of making cloths of gold, silver, and other metals, by chymical processes, occurred to me in the year 1780." Her husband and friends thought it improbable. She went on anyway, "as far as pecuniary circumstances would permit".
What did her experiments show?
Physics Today describes the method. She soaked silk in solutions of metal salts and treated it with substances such as hydrogen, sulfur or phosphorus to deposit the metal. When the silk was dried completely first, nothing happened. When it was still damp, the metal appeared, at room temperature. She concluded that water was essential. She also found that gold was reduced only in the presence of light, work that John Herschel cited in 1839 when discussing early photography.
From this she built a general scheme. Writing about charcoal reducing a metal, she argued that the carbon takes oxygen from water, while the hydrogen of the water takes oxygen from the metal, "forming a new quantity of water equal to that decomposed". So, she wrote, "a thimble full of water would be sufficient to reduce any quantity of metal; provided the water were prevented from escaping, and time enough allowed."
How does her idea look in modern equations? A worked example
Here is one way to write her scheme for carbon reducing a metal oxide, using copper(II) oxide as a modern illustration. Her own experiments used solutions of gold, silver and other metal salts.
Carbon takes oxygen from water. C + 2H₂O → CO₂ + 2H₂
Hydrogen takes oxygen from the metal oxide. 2H₂ + 2CuO → 2Cu + 2H₂O
Add and cancel. C + 2H₂O + 2H₂ + 2CuO → CO₂ + 2H₂ + 2Cu + 2H₂O. The 2H₂O and 2H₂ appear on both sides, leaving C + 2CuO → 2Cu + CO₂. Water appears in the mechanism but not in the net equation.
Check the atoms. Left: 1 C, 2 Cu, 2 O. Right: 1 C, 2 Cu, 2 O. Balanced.
Now the "thimble" claim. Using the IUPAC atomic weights H = 1.008, O = 15.999 and Cu = 63.546, H₂O = 18.015 g/mol and CuO = 79.545 g/mol.
If water were used up. 1.00 g of water is 1.00 ÷ 18.015 = 0.0555 mol. From steps 1 and 2, each mole of water gives one mole of H₂, which reduces one mole of CuO: 0.0555 × 79.545 ≈ 4.42 g of CuO, giving 0.0555 × 63.546 ≈ 3.53 g of copper. Then it stops.
If water is regenerated. Step 2 gives back all the water step 1 used, so the same gram can go round again and again. The limit is set by the carbon and oxide, not the water, exactly the point of her thimble.
The NCERT Class 12 chapter Chemical Kinetics says the same in modern terms: a catalyst forms a short-lived intermediate and is given back, and "A small amount of the catalyst can catalyse a large amount of reactants."
Common mistakes:
Cancelling before writing the steps. A catalyst only shows up in the mechanism; you must write the steps to see it.
Calling an intermediate a catalyst. H₂ is made and used up within the cycle; it is an intermediate. Water is there at the start and the end.
Assuming a catalyst changes the products. The net reaction is the same with or without it.
If writing mechanisms is where you get stuck, the Fermi Problem Library has worked problems with a step-by-step solver that explains the reasoning rather than printing an answer.
What did she get wrong, and how was she received?
She pushed the idea too far. The essay argues that water is decomposed in every case of combustion, and in one case claims that "a quantity of water double that decomposed is regenerated", a flaw later critics noted, as Physics Today reports. She also rejected both sides of the great debate of her day, the phlogiston theory and Lavoisier's oxygen theory.
Even so, Physics Today records that the essay was republished in Germany in 1798 and in the United States in 1810, and that in 1798 the Philadelphia Chemical Society elected her a corresponding member. The word catalysis first appears with Berzelius in 1835. Our posts on Wilhelm Ostwald and catalysis and collision theory and catalysts take the story on.
What can a student take from Fulhame's way of working?
Notice the condition that matters. Damp versus dry silk was the clue to water's role.
Generalise, then test. She looked for one explanation across many reactions.
Publish your evidence. Her careful record is why she can be credited today.
Know where your idea stops. The water idea fitted her reductions better than all of combustion.
Try it now: write a two-step mechanism for 2H₂O₂ → 2H₂O + O₂ with iodide ions as the catalyst, and check that I⁻ cancels in the net equation.
