A curious paper, published in the journal Chemical Communications, has managed to do something seemingly quite extraordinary: It’s made a small chemical component disappear from history. Specifically, it’s likely it has never existed, which might mean that a lot of pre-existing chemistry studies, while still largely valid, have based their work on a false assumption – a phantom ion, as it were.

This study, led by the University of Western Australia and Murdoch University, was somewhat serendipitous. 

They were undergoing a project to investigate the efficacy of sulfide solutions in reducing mercury emissions from refineries that produce alumina. This sounds incredibly niche, but it’s an important industrial conundrum involving mineral processing and environmental pollution that several studies have worked on over the years. In any case, this latest project involved some highly specified chemistry, using various compounds of and variations on sulfur.

During their investigations, they were also looking at a particular chemical species, the S^2- ion. Although this ion certainly exists in various forms, they were trying to find experimental evidence for it in an aqueous solution, a liquid where water acts as the dissolving substance (the “solvent”).

Using complex mixtures of sulfur-including chemical compounds, dissolved in hyper-concentrated aqueous solutions, they put them through a Raman spectrometer. This device uses a laser to energetically excite targeted molecules, and using the scattered light, a detector and decoding algorithm is able to work out what specific chemical species is present.

Although this wasn't a matter of simply spotting the species like a bacterium through a microscope, the team couldn't find any hints that it existed at all.

"There is no longer plausible experimental evidence for S^2- in an aqueous solution," lead author Prof. Peter May of Murdoch University, told IFLScience.

The team’s paper notes that although the “presence of significant amounts of S^2– in aqueous solution was ruled out over 30 years ago”, their new work “casts serious doubt” on the formation of any of the elusive ion whatsoever.

Although it’s pointed out that you cannot ever “prove” that a chemical species doesn’t exist, there’s simply “no credible evidence” that this particular ghostly ion does exist in an aqueous solution.

This species isn't just a minor facet of chemistry either; it has appeared in textbooks, studies and databases as a "foundation stone in sulfide thermodynamics," according to May.

As a result, the team suggests that it should be erased from the scientific literature forthwith to stop any more erroneous calculations involving sulfide systems taking place. In fact, the paper concludes on a rather strong note, demanding that the species needs to be “comprehensively banished by the chemical community.”

Blimey. Remind us never to get on the bad side of chemistry researchers.