Müller I. A history of thermodynamics. The doctrine of energy and entropy (Müller I. A history of thermodynamics. The doctrine of energy and entropy.pdf), страница 4

That sum isconserved by Newton’s laws and Hooke’s law of elasticity, although theindividual contributions might change.1 The term energy was not fullyaccepted until the second half of the 19th century when it was extrapolatedaway from mechanics to include the internal energy of thermodynamics andthe electro-magnetic energy. The first law of thermodynamics states that thetotal sum is conserved: the sum of mechanical, thermodynamic, electromagnetic, and nuclear energies. We shall proceed to describe the difficultbirth of that idea.Eventually – in the early 20th century – energy was recognized as havingmass, or being mass, in accord with Einstein’s formula E = mc2, where c isthe speed of light.Caloric TheoryIn the early days of thermodynamics nobody spoke of energy; it was eitherheat or force. And nobody really knew what heat was.

Francis Bacon(1561–1626) mentions heat in his book “Novum Organum” and – true to hisconviction that the laws of science should be gleaned from a mass ofspecific observations – he tabulated sources of heat such as: flame,lightning, summer, will-o’-the-wisp, and aromatic herbs which produce thefeeling of warmth when digested.2A little later Pierre Gassendi (1592–1655), a convinced atomist, saw heatand cold as distinct species of matter.

The atoms of cold he considered astetrahedral, and when they penetrated a liquid that liquid would solidify, –somehow.1The observation that mechanical energy is conserved is usually attributed to GottfriedWilhelm Leibniz (1646–1716), who pronounced it as a law in 1693.2 Francis Bacon: “Novum Organum’’ (1620).102 EnergyAn important step away from such interesting notions was done byJoseph Black (1728–1799).

Black melted ice by gently heating it andnoticed that the temperature did not change. Thus he came to distinguish thequantity of heat and its intensity, of which the latter was measured bytemperature. The former – absorbed by the ice in the process of melting –he called latent heat, a term that has survived to this day.The next step – unfortunately a step in the wrong direction – came fromAntoine Laurent Lavoisier (1743–1794), the pre-eminent chemist of the18th century, sometimes called the father of modern chemistry. He insistedon accurate measurement and therefore people say that he did for chemistrywhat Galilei had done for physics one and a half century before. The truenature of heat, however, was beyond Lavoisier’s powers of imagination andso he listed heat – along with light – among the elements,3 and considered ita fluid which he called the caloric. Asimov4 writes that … it was partlybecause of his [Lavoisier’s] great influence that the caloric theory …remained in existence in the minds of chemists for a half century.

The ideawas that caloric would be liberated when chips were taken off a metal in alathe (say) and thus the material became hot.Benjamin Thompson (1753–1814), Graf von RumfordBenjamin Thompson, later Graf von Rumford – ennobled by the Bavarianelector Karl Theodor – was first to seriously question the caloric theory.Thompson was born in Woburn, Massachusetts to poor parents, just likeBenjamin Franklin (1706–1790), the other famous American scientist of the18th century; their birthplaces are only two miles apart. Both, althoughcongenial as scientists, subscribed to different political views.

Indeed,Thompson supported the British in the war of independence; he spied forthem and even led a loyalist regiment, – a Tory regiment for Americanpatriots – the King’s American Dragoons.5Perforce, after the colonials had won their independence, Thompson leftAmerica and, by his intelligence and his captivating demeanour, he becamea man of the world, welcome in courts and scientific circles. He proved tobe an inventor of everything that needed inventing: a modern kitchen –complete with sink, overhead cupboards and trash slot –, a drip coffee pot,345A.L. Lavoisier: “Elementary Treatise on Chemistry” (1789).I. Asimov: “Biographical Encyclopedia of Science and Technology’’.- Pan ReferenceBooks, London (1975).Kenneth Roberts: ‘‘Oliver Wiswell.” Fawcett Publications, Greenwich, Connecticut.(1940).Benjamin Thompson (1753–1814), Graf von Rumford11and the damper for chimneys.6 Also he was a gifted organizer of anythingthat needed to be organized:x The distribution of a cheap, nourishing and filling soup – the Rumfordsoup7 – for the poor people of Munich,x the transplanting of fully grown trees into the English garden of theelector of Bavaria,x and a factory for military uniforms staffed by the beggars from thestreets of Munich.The grateful elector made him a count: Graf von Rumford, see Fig.

2.1.Rumford was a town in Massachusetts, where Thompson had lived; later itwas renamed Concord – now in New Hampshire; it was a hotbed of theAmerican revolution. Needless to say that the elector knew neither Rumfordnor Concord. Actually, one cannot help feeling that the two of them, theelector and Thompson, may have had a good laugh together: The elector,who had no jurisdiction over Rumford county and Thompson, – the newGraf von Rumford – who could not show his face there without running therisk of being tarred and feathered and made to ride a fence.Fig. 2.1.

Lavoisier and Thompson (Graf Rumford), both married to the same woman, – atdifferent timesGraf Rumford was put in charge of boring cannon barrels for the elector.He noticed that blunt drills liberated more caloric than sharp-edged ones,although no chips appeared. By letting the blunt drill grind away for somelength of time he could liberate more caloric than was known to be neededto melt the whole barrel.

Thus he came to the only possible conclusion thatthe caloric theory was bunk and that67According to Varick Vanardy: ‘‘Gen. Benjamin Thompson, Count Rumford: Tinker,Tailer, Soldier, Spy.” http://www.rumford.com.A variant of that soup was handed out in German prisons until well into the 20th century.It was then known as ‘‘Rumfutsch’’. According to Ernst von Salomon: ‘‘Der Fagebogen”[The Questionaire] Rowohlt Verlag Hamburg (1951).122 Energy…it was inconceivable to think anything else than that heat was just thesame as what was supplied to the metal as continually as heat was appearingin it namely: motion.8Considering the jargon of the time that was a direct hit. Even fifty yearslater Mayer could not express the 1st law more clearly than by saying:motion is converted to heat, – and Mayer did still shy away from saying:Heat is motion.Rumford even made an attempt to give an idea of what was later calledthe mechanical equivalent of heat.

His drill was operated by the work oftwo horses – of which one would have been enough – turning a capstan-bar,and Rumford notes that the heating of the barrel by the drillequals that of nine big wax candles.Actually, he became more concrete than that when he said that the totalweight of ice-water that could be heated to 180°F in 2 hours and 30 minutesamounted to 26.58 pounds.9 Joule fifty years later10 used that measurementto calculate Rumford’s equivalent of heat to 1034 foot-pounds.11 For thecalculation Joule adopted Watt’s measurement of one horsepower, namely33000 foot-pounds per minute.It is probably too much to suppose that Rumford thought aboutconservation of energy, but he did say this:One would obtain more heat [than from the drill], if one burned the fodderof the horses.

Thus he gave the impression, perhaps, that he may havesuspected those amounts of heat to be the same.Rumford through his arrogance and the general unpleasantness of hischaracter – so the American author Asimov12 – eventually outwore hiswelcome in Bavaria. He went to England where he was admitted into theRoyal Society. He founded the Royal Institution, an institute which may beregarded as the prototypical postgraduate school. Rumford engagedThomas Young and Humphry Davy as lecturers, who both became eminentscientists in their own time. Jointly with Davy, Rumford continued his8Rumford: “An inquiry concerning the source of the heat which is excited by friction”.Philosophical Transactions. Vol. XVIII, p.

286.9 Rumford: loc.cit. p. 283.10 J.P. Joule: “On the mechanical equivalent of heat”. Philosophical Transaction. (1850) p.61ff.11 This means that a weight of 1 pound dropped from a height of 1034 feet would be able toheat 1 pound of water by 1°F. [Joule’s best value in 1850 is 772 foot-pounds, see below.]12 I. Asimov: ‘‘Biographies….” loc.cit.Americans do not like their countryman Graf Rumford because of his involvement in thewar of independence on the side of the loyalists.

They scorn him and revile him, andlargely ignore him. This is punishment for a person who fought on the wrong side – theside that lost. We must realize though that the American revolutionary war was as much acivil war as it was a war against the British rule; and civil wars have a way of arousingstrong feelings and long-lasting hatred.Robert Julius Mayer (1814–1878)13experiments on heat: He carefully weighted water before and after freezingand found the weight unchanged, although it had given off heat in theprocess. Therefore he concluded that the caloric, if it existed, wasimponderable.