How our understanding of matter transformed from mystical alchemy to modern molecular science
Chemistry is often pictured as test tubes and explosions, but at its heart, it is a science perpetually in development, a philosophy of matter constantly redefining itself. For centuries, thinkers have grappled with a deceptively simple question: what is a substance, and how does it transform? The journey to an answer has been a revolution not just in technique, but in thought itself.
This article traces that intellectual growth, showing how chemistry matured from a mystical art into a modern science, and how it continues to evolve by confronting new complexities. We will explore how a single, clever experiment shattered a long-held theory and set the stage for the chemistry we know today.
The development of chemistry represents a shift from qualitative, mystical explanations to quantitative, evidence-based understanding. This transformation didn't just change how we do chemistry—it changed how we understand reality itself.
To understand chemistry's development, one must grasp the foundational ideas that form its conceptual core. These are not just facts, but philosophical positions on the nature of reality 4 .
The cornerstone of chemistry is the ability to distinguish between mixtures and pure substances. A pure substance, whether an element or a compound, has characteristic and invariant properties 2 .
Elements are substances that cannot be broken down into simpler substances by chemical means. Compounds are formed from chemical combination of elements with different properties 2 .
Physical properties can be observed without changing the substance. Chemical properties refer to reactions that transform substances into new ones 2 .
Recent philosophical reflections suggest that contemporary chemistry is characterized by a "potentially endless diversity of matter" and an "open-ended variety of aims and interests" 4 . This has led to a search for the "chemical core of chemistry," the characteristic parts that can be distinguished from its many interdisciplinary and applied subfields 4 .
Before the 18th century, the dominant theory of combustion was the phlogiston theory. Proposed by Georg Stahl, it stated that combustible materials contained a fire-like element called "phlogiston." When a substance burned, it released its phlogiston into the air 2 .
This seemed logical—burning wood turns to ash, something appears to be lost. The theory was a classic "mythical conception," explaining qualities through the combination of a few basic principles 2 .
However, it had a critical flaw: it could not adequately explain why metals often gained weight when they were calcined (heated in air). If phlogiston was being lost, shouldn't the metal get lighter?
The theory that combustible materials contain "phlogiston" which is released during burning.
Dominant theory until late 18th century
Early theories of fire as one of the classical elements (earth, air, fire, water)
Johann Joachim Becher proposes theory of terra pinguis, a precursor to phlogiston
Georg Ernst Stahl formally proposes phlogiston theory
Experiments by Lomonosov, Black, and others challenge phlogiston theory
Lavoisier develops oxygen theory of combustion, replacing phlogiston
The downfall of phlogiston theory is a classic tale of how careful experimentation can overturn entrenched beliefs. In the 1750s, the Russian scientist Mikhail V. Lomonosov revisited experiments conducted by Robert Boyle decades earlier 2 .
Boyle heated metals like tin in open glass retorts. He observed that after heating, the resulting calx (the powdery oxide) was heavier than the original metal. He concluded this was because "fire material" had passed through the glass and combined with the metal 2 .
Lomonosov repeated Boyle's experiment with one crucial change: he weighed the sealed retort after heating but before opening it 2 . This single adjustment controlled for a key variable—the outside air.
A known quantity of a metal (e.g., tin) was placed into a sturdy glass retort.
The retort was sealed to make it airtight.
The entire sealed apparatus was weighed to obtain an initial mass.
The retort was heated strongly, allowing the metal inside to calcine.
After cooling, the sealed retort was weighed again.
Finally, the retort was opened, and the calx inside was weighed separately.
Lomonosov's results were definitive. He discovered that when the retort remained sealed, its total weight was unchanged by the heating process. However, upon opening the vessel, air rushed in, and only then did the calx inside show an increase in mass. This proved that the weight gain of the metal was not due to capturing a mysterious "fire material," but to combining with a component from the air itself 2 .
Lomonosov's work provided strong evidence for the conservation of matter—the principle that matter is neither created nor destroyed in a chemical reaction—and directly contradicted the phlogiston theory 2 . This experiment paved the way for Antoine Lavoisier, who would later identify oxygen and establish the modern theory of combustion.
| Results of Lomonosov's Sealed Vessel Experiment | |||
|---|---|---|---|
| Experimental Condition | Observation of Metal Calx | Total Mass of Sealed Vessel | Inference |
| Before Heating | Shiny metal | Mass M | -- |
| After Heating (Vessel Sealed) | Formed a calx | Mass M | No mass change; matter is conserved. |
| After Heating (Vessel Opened) | Calx remained | -- | Air rushed in, then calx was heavier. |
| Key Conclusion | The calx gains mass by combining with a component from the air, not by losing phlogiston. | ||
| Philosophical Shift: Alchemy vs. Modern Chemistry | |
|---|---|
| Alchemical/Mythical View | Modern Chemical View |
| Obscure, allegorical, mystical 2 | Clear, well-defined concepts 2 |
| Possible (e.g., lead to gold) 2 | Not achievable by chemical means 2 |
| A few qualitative principles (e.g., Salt, Sulphur, Mercury) 2 | Quantitative elements defined by experiment |
| Synthetic, dynamic, personified 2 | Analytical, mechanical, mathematical 2 |
The evolution of chemistry has depended on the tools and materials at its disposal. The shift from alchemy to chemistry required reliable, pure substances to conduct reproducible experiments. Below is a sample of foundational reagents that would be found in a modern laboratory, crucial for exploration and discovery.
Example: Ethanol, Acetone
Dissolving non-polar compounds, cleaning glassware, crystallizing products.
Example: Phenolphthalein
Signaling the endpoint of an acid-base titration by changing color 7 .
The story of chemistry is a powerful reminder that science is not a static collection of facts but a dynamic, developing entity. Its history is marked by profound shifts—from the mythical to the mechanical, from qualitative principles to quantitative laws 2 . The simple, controlled experiment of Lomonosov was a developmental milestone that helped the discipline shed an outdated theory and mature.
Today, the philosophical development of chemistry continues. Theorists argue that future progress depends on the field's ability to integrate diversity and larger social-cultural systems, and to consider the influence of the world views in which theories are developed 1 .
Even as it delves deeper into the quantum realm, chemistry retains its core focus: the composition, properties, and breathtaking transformations of matter. It is a science that has grown up, but has never stopped growing.