Rethinking Chemistry's History Through Multiple Transformations
Exploring the three fundamental transformations that shaped modern chemistry between the late 18th and 19th centuries
What does it mean for a science to have a revolution? For centuries, we've been taught that chemistry had a single, defining revolution at the end of the 18th century, when Antoine Lavoisier overthrew the phlogiston theory and established oxygen as the key to understanding combustion. But what if this familiar narrative is too simplistic? Historical research now suggests that chemistry didn't have just one revolution—it underwent at least three fundamental transformations between the late 18th and 19th centuries.
This article explores these revolutionary periods that transformed chemistry from a mystical art into the quantitative science we know today, reshaping how we understand matter at its most fundamental level.
Lavoisier's Oxygen Theory
Late 18th Century
Atomic Theory
Early 19th Century
Structural Chemistry
Mid 19th Century
Before we can understand the revolutions, we must first understand what was revolutionized. For much of the 18th century, the dominant theory in chemistry was phlogiston theory. This theory posited that combustible materials contained a fire-like element called phlogiston, which was released into the air during burning 1 . What we now recognize as combustion was viewed as a decomposition process—when wood burned, it decomposed into phlogiston (which escaped) and ash (which remained) 1 .
Antoine Lavoisier, often called the "Founder of Modern Chemistry," would not be constrained by the old framework 1 . In a series of meticulous experiments using precise measurements, he demonstrated that combustion involved combination with a component of air, not the release of phlogiston.
Heat mercury in a sealed container
Forms red calx (mercury oxide)
Mass increases after heating
Heat calx strongly to decompose
Releases oxygen gas, reforms mercury
Lavoisier's quantitative approach proved that burning was not decomposition but chemical combination—specifically, combination with oxygen from the air 1 . This simple but precise experiment, coupled with his formulation of the law of conservation of mass, marked the first chemical revolution. The balance became chemistry's fundamental instrument, and Lavoisier established a new chemical nomenclature that forms the basis of our modern naming system 1 .
| Aspect | Phlogiston Theory | Lavoisier's Oxygen Theory |
|---|---|---|
| Nature of Combustion | Decomposition (release of phlogiston) | Combination with oxygen |
| Mass Change During Burning | Substances should lose mass | Substances gain mass |
| Role of Air | Serves as reservoir for phlogiston | Provides oxygen for combination |
| Conceptual Framework | Qualitative | Quantitative, based on measurements |
If Lavoisier's work constituted the first chemical revolution, a second emerged in the early 19th century with the rise of atomic theory and the concept of definite proportions. John Dalton, building on Lavoisier's quantitative approach, proposed that all matter is composed of atoms, and that chemical compounds form when atoms of different elements combine in fixed ratios 6 .
This period was marked by intense debate and experimentation. Joseph Proust's law of definite proportions (1801) stated that chemical compounds always contain the same elements in the same proportion by mass, regardless of how they were prepared 1 . This was contested by Claude Louis Berthollet, who argued for variable composition, but Proust ultimately prevailed after eight years of controversy 1 .
Dalton's atomic theory, published in his "New System of Chemical Philosophy" (1808), provided a theoretical framework that explained why compounds had definite compositions 6 . He proposed that each element consisted of identical atoms, and that chemical compounds formed when atoms of different elements combined in simple whole-number ratios.
The acceptance of atomic theory transformed how chemists understood and investigated matter:
| Year | Scientist | Contribution | Impact |
|---|---|---|---|
| 1801 | Joseph Proust | Law of Definite Proportions | Established that compounds have fixed composition |
| 1804 | John Dalton | Law of Multiple Proportions | Supported atomic theory through combining ratios |
| 1808 | John Dalton | Atomic Theory | Proposed matter composed of atoms that combine in fixed ratios |
| 1811 | Amedeo Avogadro | Avogadro's Hypothesis | Distinguished between atoms and molecules |
| 1814 | Jöns Jakob Berzelius | Accurate Atomic Weights | Provided essential quantitative data for elements |
The third chemical revolution emerged mid-19th century with the development of structural chemistry and the periodic system. As more elements were discovered and their properties studied, chemists began to recognize patterns that pointed toward an underlying organization of matter.
Friedrich Wöhler's 1828 synthesis of urea from inorganic ammonium cyanate struck a blow against vitalism—the theory that organic compounds could only be produced by living organisms through a "vital force" 2 6 . This discovery helped unify organic and inorganic chemistry and suggested that the same laws governed all matter.
Dmitri Mendeleev and Lothar Meyer independently discovered that when elements are arranged by atomic weight, their properties recur periodically 1 . Mendeleev's genius was in leaving gaps for undiscovered elements and accurately predicting their properties.
The 19th century also saw crucial advances in chemical instrumentation. Bunsen and Kirchoff's development of the spectroscope in 1859-60 revolutionized chemical analysis and led to the discovery of seven new elements (rubidium, cesium, thallium, indium, gallium, scandium, and helium) by analyzing their characteristic emission spectra 1 .
| Element Prediction | Predicted Properties | Actual Element (Discovery Year) | Actual Properties |
|---|---|---|---|
| "Eka-boron" | Atomic weight ~44, oxide formula Eb₂O₃ | Scandium (1879) | Atomic weight 44.96, oxide formula Sc₂O₃ |
| "Eka-aluminum" | Atomic weight ~68, density 5.9 g/cm³ | Gallium (1875) | Atomic weight 69.7, density 5.9 g/cm³ |
| "Eka-silicon" | Atomic weight ~72, density 5.5 g/cm³ | Germanium (1886) | Atomic weight 72.6, density 5.3 g/cm³ |
The chemical revolutions were enabled by advances in laboratory materials and instruments. Key research reagents and tools included:
Lavoisier's precise balances enabled quantitative chemistry and the law of conservation of mass 1
Bunsen and Kirchoff's instrument allowed elemental identification through spectral analysis 1
Alessandro Volta's battery (1800) enabled electrolysis, allowing Davy to isolate elements like sodium and potassium
Used in air pumps and for trapping gases in pneumatic experiments 6
Key reagent in early photography and chemical analysis 3
Used as a catalyst in contact process for sulfuric acid production 1
Viewing chemistry's history through the lens of three revolutions rather than one provides a richer, more accurate narrative of how this fundamental science developed. Each revolution built upon the previous while introducing transformative new concepts:
Established chemistry as a quantitative science and introduced the conservation of mass.
Provided a particulate theory of matter that explained chemical combination.
Revealed patterns in elemental properties and molecular architecture.
This more nuanced historical view reminds us that scientific progress rarely occurs through a single breakthrough, but through successive waves of conceptual transformation. Each revolution provided new tools, both conceptual and instrumental, that enabled the next advance.
The teaching of chemistry benefits from recognizing these multiple revolutions, as it highlights how scientific knowledge evolves through contested ideas, crucial experiments, and the gradual accumulation of evidence—a process that continues in chemistry laboratories to this day.