The Newton of Chemistry

In his terrific history of chemistry, Mendeleyev’s Dream, Paul Strathern pointed out the impact of what Newton did to physics and science in general:

“Any scientific advances were expected to incorporate the mechanical rigor and mathematical exactitude of Newtonian physics.”

Poor chemistry. It still belonged to the “world of quality”, not quantity.

And so chemistry would stay until Antoine Lavoisier came along a century later. He believed in weighing and measuring. He made a leap of faith and assumed that while “substances taking part in a chemical reaction could be transformed, but their overall weight would be the same”. If he had just made an assumption that was later proven true and is now a bedrock of science itself, it could be dismissed as a lucky guess. But Lavoisier performed experiments based on his assumption and the conclusions he drew changed chemistry.

For example, he had seen that water boiled for hours produced a sediment on the flask it was boiled in. While others thought this proved water had the ability to produce matter (sediment), Lavoisier decided to measure. His experimental setup consisted of a sealed system: boil water, condense the resultant steam, repeat the loop… for 101 days. He weighed the water before and after the experiment: it weighed exactly the same. But the sediment had been formed. So it couldn’t have come from the water. The weight of the glass containers used in the experiment had reduced by the same amount as the sediment formed. Ergo, the sediment “had been extracted from the glass by the boiling water”, said Lavoisier.

In an earlier blog, I already talked of Lavoisier’s role in proving the phlogiston theory of combustion wrong and identifying the role of oxygen instead, so I won’t repeat that Lavoisier achievement here. If you re-read that, you’ll see he’d arrived at that conclusion/proof via measurements.

Lavoisier then measured the oxygen concentration in the air we breathed in v/s the air we breathed out, thereby proving that respiration was somewhat similar to combustion, at least to the extent that both processes consumed oxygen.

But the man wasn’t done yet. He noticed that chemistry was a mess of names, oxygen v/s “dephlogisticated air” to name just one. The confusion was worse when it came to names of compounds. Worse, different languages had different names, and different fields within the same language (e.g. medicine v/s geology) had different names for the same things! In 1787, Lavoisier proposed a rational nomenclature e.g. compound names should be based on the elements they were composed of. Shakespeare may say a name doesn’t matter, but:

“It is almost impossible to exaggerate the importance of this step. Such a language even became a scientific instrument in itself.”

He went further and said an element was whatever we hadn’t broken yet into simpler constituents, the key phrase being “hadn’t broken yet”. Why was this such a big deal? Because:

“Chemistry was learning to admit what it did not know – and thus gain a deeper understanding of precisely what it did know.”

So yes, the man came up with law of conservation of matter. He disproved the phlogiston theory. He defined elements in pragmatic terms. But most importantly, he changed the way chemistry would be done from his time onwards. Is it at all a surprise then that Lavoisier is known as the “Newton of chemistry”?