Communicating science


Who is Svante Arrhenius?

On my way to the office on the Stockholm University campus, I walk down Svante Arrhenius väg, past a bronze bust of Svante Arrhenius and the Arrheniuslaboratorierna (Arrhenius Laboratories).

So, who is he? While I learned about Arrhenius’ work in chemistry classes, I feel compelled to refresh my memory.

Arrhenius was a Swedish chemist (1859 – 1927). At an young age, he showed great skill in math and went on to study chemistry and physics at Uppsala University and the Royal Swedish Academy of Sciences. In 1884, Arrhenius presented his doctoral dissertation, which described experiments with the electrical conductivity of dilute solutions. He proposed that dissolving salts, acids, and bases in water produces positively and negatively charged particles.

His ideas were particularly impressive considering that they came 13 years before the discovery of the electron, the subatomic particle responsible for the creation of positively and negatively charged particles (ions). Atoms have a neutral charge, but when one loses an electron it becomes a positively charged particle (cation). When an atom gains an electron, it becomes a negatively charged particle (anion).

For example, consider a substance in your kitchen, table salt, aka sodium chloride or NaCl. When NaCl dissolves in water, it produces Na+ (sodium missing an electron) and Cl- (chlorine with an extra electron). These electrically charged ions allow the solution to conduct electricity.

Arrhenius is also known for his method of classifying acids and bases. He defined acids as substances that produced hydrogen ions (H+) when dissolved in water. Bases are substances that produced hydroxide ions (OH-) in water. Common household (and Arrhenius) acids include vinegar (acetic acid), carbonic acid (in soft drinks), and citric acid (orange juice). Common Arrhenius bases are lye (caustic soda) and milk of magnesia.

Arrhenius’s definition has its limitations and does not describe all acid-base chemistry, so modern chemists prefer other definitions that cover a broader range of chemical reactions. Nonetheless, the concept of Arrhenius acids and bases are still taught in chemistry classes today.

When Arrhenius presented his dissertation, his ideas were considered speculative and were not well received. He was not deterred, however, and he further developed and extended his theory of “electrolytic dissociation” in more quantitative terms. Ultimately, he won a Nobel Prize for this work in 1903.

Greenhouse effect

Arrhenius was also the first person to investigate the relationship of atmospheric CO2 concentrations and global temperatures. I had forgotten this until I started reading about his life.

In 1896, Arrhenius presented “On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground.” This paper described the radiative effects of CO2 (carbonic acid) on temperature and proposed that increasing atmospheric CO2 concentrations would increase global temperatures (and the reverse). This work was a “thought experiment” where he applied basic scientific principles and the work of other scientists to climate. Arrhenius was not concerned with CO2 released by fossil fuel combustion, but was interested in finding an explanation for changes in temperatures due to ice ages. This work was the foundation for modern climate science.

Chemical reactions like it hot

We all know that food spoils faster on the kitchen counter than when stored in the refrigerator. Or that food cooks faster at higher temperatures. You might not think in these terms, but these are chemical reactions! Prior to Arrhenius, scientists observed that the rate of chemical reactions increased with increasing temperatures and that this increase was not linear. In 1889, Arrhenius proposed an equation (k = Ae-Ea/RT) to explain why. He argued that that molecules must acquire a minimum amount of energy (activation energy) in order for chemical reactions to occur. One generalization of this equation is that reaction rates double for every 10 °C increase in temperature. Something to think about the next time you are using your stove…and if you want to learn more about applying the Arrhenius equation in your kitchen, check out this.

Now I feel like I better know (and appreciate) Arrhenius and will say "hej" when I walk past his bust each day.

Svante ArrheniusSvante Arrhenius, outside the laboratory building that bears his name on the Stockholm University campus

Michelle McCrackin

Michelle McCrackin