Archive for September, 2012

The house in Manchster where neighbour trouble broke out. Photo credit: Charlie Hulme

The house in Manchester where neighbour trouble broke out. Photo credit: Charlie Hulme

We all have our problems. And those engaged in the business of scientific discovery are no strangers to it. Budget cuts, lack of resources, experiments that fail, theories that fall apart, and so on. Rarely though does trouble with the neighbours derail one’s research programme.

Yet curiously, this is exactly what happened to the research conducted in the 1850s by James Joule and William Thomson [later Lord Kelvin] into the expansion of gases – pioneering work that led to the discovery of the Joule-Thomson effect before their endeavours were brought to an abrupt end.

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In the late 1840s, Henri Regnault in France published the most accurate data so far attained of the pressure volume relationship of air maintained at constant temperature. Although the data substantially confirmed Boyle’s law, or Mariotte’s law as Regnault would have called it, the results nevertheless revealed a small discrepancy, in that the density of air increased slightly more than expected in relation to pressure.

Hardly a big deal you might think, but to those involved in the newly-forming, cutting-edge science of Thermo-dynamics as it was spelled then, the discrepancy suggested that there should be a similarly small cooling effect when air expands through a throttle into a region of lower pressure. Here was an opportunity to study the behaviour of real gases in motion and explore their differences, however slight, from ideal behaviour. At Glasgow University in Scotland, the maverick Professor William Thomson designed an innovative steady state experimental method, for which he had a collaborator of proven experimental skill in mind – Mr James Joule of Manchester.

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James Joule, the son of a brewery owner, had a passion for experimentation and from an early age had been conducting scientific experiments at home which had convinced him that heat could be created by mechanical means, and that there was a precise quantitative relationship between the two. This was in stark opposition to the tenets of the caloric theory, which at the time was the prevailing belief of the scientific establishment. But Joule was not a member of the scientific establishment, and this freed him from peer pressure and allowed him to pursue his own ideas and increasingly refined experimentation.

There was a downside to Joule’s non-membership of Britain’s scientific club, however. None of its members took any notice of him, or what he had to say. To them he was an uneducated commoner, an amateur, an outsider.

Joule’s collected papers, which can be read online at archive.org, chart his tireless yet fruitless efforts to get either the Royal Society or the British Association for the Advancement of Science to take notice of his discovery. He kept at it, without luck, for four years. And then one day, in 1847, his luck changed. As Joule himself wrote in a subsequent note:

“It was in the year 1843 that I read a paper “On the Calorific Effects of Magneto-Electricity and the Mechanical Value of Heat” to the Chemical Section of the British Association assembled at Cork … the subject did not excite much general attention, so that when I brought it forward again at the meeting [in Oxford] in 1847, the chairman suggested that I should not read my paper but confine myself to a short verbal description of my experiments. This I endeavoured to do, and discussion not being invited, the communication would have passed without comment if a young man had not risen in the section, and by his intelligent observations created lively interest in the new theory. The young man was William Thomson, who had two years previously passed the University of Cambridge with the highest honour, and is now [1855] probably the foremost scientific authority of the age.”

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Foremost scientific authority he may later have been, but the fact is that William Thomson was at the time of the Oxford meeting a staunch supporter of the yet-to-be-discredited caloric theory, and history shows that his conversion to the dynamical theory that James Joule espoused was somewhat slow – some would even say reticent. But by 1852, Thomson was sufficiently convinced that heat and work were interconvertible, in the quantitative ratio that Joule had discovered.

Now, with Regnault’s discoveries waiting to be tested,  the two men were ready to embark on their first collaborative work (Joule having been admitted to the Royal Society in the meantime, thus making him eligible for research grants). Some accounts suggest that their collaboration was conducted by correspondence, with Thomson in Glasgow devising experiments and analysing results while Joule did the experimental work in Manchester. But an account of Joule’s life by Osborne Reynolds (he of the Reynolds number) shows that Thomson made several trips to Manchester and seems to have enjoyed his visits. In one recollection, Thomson writes of Mr and Mrs Joule that “both she and he showed me the greatest kindness during my visits to them in Manchester for our experiments on the thermal effects of fluid in motion”.

The experiments involved forcing a gas under constant pressure through a tube, narrowed at one point along its length to act as a throttle, and open to the atmosphere at the distal end. Thermometers were positioned in the flow to measure the temperature of the gas on entering and exiting the throttle. The first experiments, using air,  were conducted in one of the cellars of the Joule’s family home at 1 Acton Square, Manchester, opposite what is now the campus of the University of Salford.

Although some cooling was detected, the effect was very small and it became quickly clear that the apparatus needed to be scaled up, and the pressures increased. So with a forcing pump furnished by a grant from the Royal Society, the experiments were moved to the family’s brewery in New Bailey Street Manchester. This was later followed by yet another round of upscaling, this time with the installation of a full size steam engine to drive the pressure pump, again financed by the Royal Society. The design of the throttle was refined with the use of a porous plug rather than a single small orifice, and the gases used in the experiments now included hydrogen and what was referred to as carbonic acid, which we now call carbon dioxide.

It must have been a sight to see Joule and Kelvin, who would ultimately have their names commemorated in the units of energy and absolute temperature respectively, up to their elbows in engine oil and slaving away in the dank cellars of a Manchester brewery to keep their hugely pressurised apparatus in a steady state and obtain meaningful measurements. If someone had taken a photograph of them, it would be worth gold now.

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The next few years brought personal tragedy to Joule, with the death of his newborn second son, closely followed by the death of his wife. During this painful time he sold the brewery and moved back to his father’s house with his young son and daughter, and his steam engine. His elder brother Benjamin writes of how Joule threw himself into continued experimental work at this time:

“My brother was very busy with experiments, many of which were decidedly dangerous owing to the pressure he made use of. During this period, for some months he could not find time to take his meals properly – just ran in and out again. The experiments were so delicate that many were carried out in the night, because a [horse-drawn] cab or cart passing along the road disturbed them, though the laboratory was at the back of the stables.”

Then tragedy struck again with the death of Joule’s father. The house was sold, and Joule moved on yet again, this time buying a house in Old Trafford (the district where Manchester United’s stadium is today). He took with him all the Joule-Thomson experimental apparatus, including the steam engine.

And it was at this point that the neighbour trouble appeared.

There was an obscure item in the house purchase deed that prohibited any steam engine being used at the property. This fact was known to the occupant of the neighbouring property, who insisted upon its strict observance despite it being an obsolete clause, and despite protests from other more lenient and understanding local residents.

Joule’s experiments juddered to a sudden halt, and although he reacted by putting his newly acquired home up for sale, it was an empty gesture and the incident seemed to deflate him. His brother Benjamin wrote of Joule suffering  “a great and lasting disappointment”, and noting that “what really affected him was the refusal to be allowed the use of his one-horse power steam engine … My brother was anticipating a series of important experiments in conjunction with W. Thomson, for which a grant had been obtained.”

In his collected papers, Joule himself couches his disappointment in more detached language:

“[William Thomson and I] pursued the discussion of the thermal effects of fluids in motion until the experiments were interrupted by the action of the owners of the adjacent property, who on the strength of an obsolete clause in the deeds of conveyance, threatened legal proceedings, the cost of which I did not feel disposed to incur”.

Joule and Thomson, the latter having lately suffered a debilitating fall,  experimented no more after this setback. The threat of legal action by a perverse individual ended an historically important piece of research.

But the work performed by the dynamic duo, and the series of joint papers they published, established the Joule-Thomson effect and the knowledge that throttled (real) gases can cool or heat on expansion depending on whether they are below or above their inversion point. This knowledge, and the equations that attach to it, are of great practical importance to today’s chemical engineers in the liquefaction of gases, refrigeration and many other fields of application.

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Related blog posts

Joule, Thomson, and the birth of big science
The story of how Joule and Thomson’s extraordinary collaboration in the 1850s propelled experimental research into the modern era. The second part of this post also explains the thermodynamics of the Joule-Thomson effect.

The Liquefaction of Gases – Part I
The story of how the scientific community came to realise that the term ‘non condensable’ gases was a misnomer, and the role that the Joule-Thomson effect had in enabling the commercial liquefaction of air.

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