Dalton and Berzelius

In his page-turning history of chemistry, Mendeleyev’s Dream, Paul Strathern describes John Dalton, the modern reviver of the idea of atoms thus:

“Dalton seems to have had a knack for wasting his scientific enthusiasm, and considerable talent, for inappropriate subjects.”

Building on Louis-Joseph Proust’s law of definite proportions (all compounds consisted of elements in simple ratios by weight e.g. 2:1 or 3:2, but never 3.23:1), Dalton realized this could be explained if all matter consisted of tiny indivisible particles: if one particle of one element could only combine with N (any integer) particles of the other, it followed the ratio of the two would always be N:1 (an integer ratio).

We take the idea of atoms for granted today that it is hard to grasp that “this momentous idea transformed our understanding of matter”. Richard Feynman did understand the point, which is why he famously said that if only one scientific idea could be passed onto future generations, then that statement should begin with: “All things are made of atoms…”.

When Dalton died, he wanted a simple funeral. Instead, he got 40,000 mourners and a hundred carriages!

“(Chemistry) had become respectable, even worthy.”

But chemistry was still very chaotic, with no standard notations for describing how elements/compounds combined. John Berzelius solved that. Remember Lavoisier, the Newton of chemistry, who drove the idea of standardized names (but not notations) for chemicals? Berzelius went further and decided that all elements should be represented by the first letter of their name in Greek or Latin. If two elements started with the same letter, then the second letter would be used to differentiate.

What’s the big deal with that, you ask. Aha, combine that nomenclature with the fact that elements combined only in integer ratios, and compounds could be denoted as CO or CO₂. The representation now conveyed constituent elements as well as the ratio in which they combined.

“Chemistry at last had its own universal language, like mathematics.”

The benefit of this notation went even further. It showed the “precise relative proportions required for (and produced by)” a chemical reaction e.g.

Zn + 2 HCl = ZnCl₂ + H₂

As Strathern wrote:

“Chemical formulae, just like mathematical formulae, had to balance out.”

Given the impact of the notation, no wonder Strathern wrote:

“For chemistry, this (notation) was the equivalent of mathematics changing from Roman to Arabic numerals.”