In Print: Lord Kelvin’s Experiments

The Newscripts blog would like to be closer Internet buddies with our glossy print Newscripts column, so here we highlight what's going on in this week’s issue of C&EN.
Kelvin experiment

Credit: Stuart Forsyth/University of Glasgow

This week's column got started when astute reader Don Borseth wrote in to question something the Newscripts gang had put in a column a few weeks ago—that the famous University of Queensland pitch-drop experiment was the longest-running laboratory experiment. The folks at Guinness World Records seem to think so, but Borseth was dubious. He recalled Lord Kelvin's diffusion experiment at the University of Glasgow from the 19th century. That experiment was set up in 1872, when the pitch-drop's creator Thomas Parnell was no more than a twinkle in his father's eye. If it was still ongoing, wasn't it the elder statesman of experiments? The Newscripts gang loves getting reader mail, particularly when we can get a new column out of it. That Kelvin's experiment is at the University of Glasgow was icing on the cake for this reporter since my husband is an alum from the school's chemistry department (Go Glasgow!). I wondered if my husband had even seen Kelvin's experiment, maybe visited it as part of his studies. As it turns out, he had never even heard of it. And so the hunt was on. I got in touch with a Lee Cronin, a Glasgow chemistry professor I met years ago at a meeting in Portugal, to see if he knew anything about Kelvin's experiment. Indeed, Cronin told me, when the pitch-drop was making headlines in July he was also doubtful of its claim to be the longest-running laboratory experiment. But the internet offered little in the way of evidence of Kelvin's diffusion setup. All I could find was this brochure on this history of the room that houses the experiment. I sought out David Lindley, author of the Kelvin biography "Degrees Kelvin: A Tale of Genius, Invention, and Tragedy" to see what he could tell me about Kelvin's work in this area.
One of Kelvin's pitch pool experiments with corks floating in pitch. Credit: The Hunterian Museum and Art Gallery, University of Glasgow

One of Kelvin's pitch pool experiments with corks floating in pitch. Credit: The Hunterian Museum and Art Gallery, University of Glasgow

"I have to confess I don't know about the diffusion experiment you mention," he wrote to me. But coincidentally, he said, the news of the pitch-drop had got him thinking about Kelvin. "I read in several places about the Australian pitch-drop experiment, and it reminded me of one of Kelvin's lecture demonstrations, in which he would put some metal bullets on top of a slab of some sort of pitch, and corks below—after a time, supposedly, the bullets drop through and the corks bob up. My understanding is that he liked to do this as a demonstration for students, so I suppose he must have used a fairly soft kind of pitch." Lindley even did a little sleuthing and found a couple of pitch-related items from the University of Glasgow's Hunterian museum here and here. As for the diffusion experiment, the folks at Glasgow's office of communications sent me some photos of the set up and said it hadn't been disturbed despite two renovations to the room. But they couldn't say for sure if it was technically still running. Unlike the pitch experiment, it has no official custodian, but that seems to beg an existential question: Is an experiment still running if no one is watching it? I contacted the press office at Guinness World Records to see if they had any thoughts on the matter. No reply from them yet. So it goes in the world of old experiments.  

Author: Bethany Halford

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