Isotopes could be pleiads

Two men vied to name stable forms of elements with differing masses (e.g. 206Pb, 207Pb, 208Pb). Today we know these are not different elements as originally thought, but rather different isotopes of in this case lead. Frederick Soddy, who received the Nobel Prize for Chemistry in 1921, provided the name isotope and argued in Nature in his intra atomic charge letter against elements with differing masses being distinguished by electronic changes (Soddy 1913). It was Kasimir Fajans, a Polish American physical chemist, who suggested around the same time that they should be called pleiads. But there’s more to the name isotope than suggested in the early literature.

While Soddy is attributed with coining the term isotope from Greek words iso - ‘equal’ + topos ‘place’ (because the isotopes occupy the same place in the periodic table of elements), it was actually suggested to him by a woman. Margaret Todd, a pioneering women doctor and an author was reportedly a family friend of the chemist Frederick Soddy. It has been suggested that at a dinner party Soddy was describing his research on radioactive elements to Todd and how despite having a different atomic mass, they occupy the same place on the periodic table. Todd suggested that such atoms could be named isotopes after the Greek words.

So how does all this relate to our research – well our recent paper explored the potential of sulfur isotopes in biominerals to be used to address a range of ecological questions. Most of the research to date on sulfur isotopes has however focused on organic tissues rather than biominerals. Biominerals have a number of advantages including the potential to retain a permanent and temporally resolved chemical record over the life time of the organism. Several studies on biominerals (otoliths) have focused on salmonids and distinguishing hatchery from wild fish or fish of different ecotypes (e.g. anadromous or otherwise).

Our research investigated whether sulfur isotope ratios in fish otoliths were influenced by ambient water or diet. The results found that biogenic carbonate (otoliths) recorded sulfur isotope ratios and that diet was not the sole source of variation in sulfur. The challenges remain finding affordable and accessible instrumentation to analyse larger sample sizes – we are after all ecologists – and obtaining homogenous standards for carbonates. We believe that here is much untapped potential to use sulfur isotopes in biominerals including possibilities for tracking hypoxia and sulfur dioxide emissions.

The image above shows the house at the University of Glasgow in which the dinner party occurred. The red arrow indicates the location of the plaque (to the left).


Doubleday ZA, J Cliff, C Izzo, BM Gillanders (2018) Untapping the potential of sulfur isotope analysis in biominerals. Marine Ecology Progress Series 598: 159-166. Open access.

Frederick Soddy Biographical. The Nobel Prize in Chemistry 1921

Margaret Todd’s Immortal Word Turns 100

Nagel M (1982) Profiles in chemistry. Frederick Soddy: From Alchemy to Isotopes. Journal of Chemical Education. 59 (9): 739 DOI: 10.1021/ed059p739

Soddy F (1913) Intra-atomic charge. Nature 92(2301): 399-400


Dinner party plaque – Glasgow, Scotland/glasgow044

Frederick Soddy image Frederick Soddy image – The Nobel Prize Frederick Soddy biographical

House image – from twitter @OssianLore 10 Nov 2017

Margaret Todd image – Margaret Todd (Wikipedia/ Public Domain)