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Boyle's law (sometimes referred to as the Boyle–Mariotte law, or Mariotte's law) is an experimental gas law which describes how the pressure of a gas tends to decrease as the volume of a gas increases. A modern statement of Boyle's law is
Mathematically, Boyle's law can be stated as : or : where ''P'' is the pressure of the gas, ''V'' is the volume of the gas, and ''k'' is a constant. The equation states that product of pressure and volume is a constant for a given mass of confined gas as long as the temperature is constant. For comparing the same substance under two different sets of condition, the law can be usefully expressed as : The equation shows that, as volume increases, the pressure of the gas decreases in proportion. Similarly, as volume decreases, the pressure of the gas increases. The law was named after chemist and physicist Robert Boyle, who published the original law in 1662.〔J Appl Physiol 98: 31-39, 2005. Free download at (Jap.physiology.org )〕 ==History== (詳細はRichard Towneley and Henry Power.〔See: * Henry Power, ''Experimental Philosophy, in Three Books'' … (London, England: Printed by T. Roycroft for John Martin and James Allestry, 1663), pp. 126-130. Available on-line at: (Early English Books Online ). On page 130, Power presents (not very clearly) the relation between the pressure and the volume of a given quantity of air: "That the measure of the Mercurial Standard, and Mercurial Complement, are measured onely by their perpendicular heights, over the Surface of the restagnant Quicksilver in the Vessel: But Ayr, the Ayr's Dilatation, and Ayr Dilated, by the Spaces they fill. So that here is now four Proportionals, and by any three given, you may strike out the fourth, by Conversion, Transposition, and Division of them. So that by these Analogies you may prognosticate the effects, which follow in all Mercurial Experiments, and predemonstrate them, by calculation, before the senses give an Experimental () thereof." In other words, if one knows the volume V1 ("Ayr") of a given quantity of air at the pressure p1 ("Mercurial standard", i.e., atmospheric pressure at a low altitude), then one can predict the volume V2 ("Ayr dilated") of the same quantity of air at the pressure p2 ("Mercurial complement", i.e., atmospheric pressure at a higher altitude) by means of a proportion (because p1 V1 = p2 V2). * Charles Webster (1965) "The discovery of Boyle's law, and the concept of the elasticity of air in seventeenth century," ''Archive for the History of Exact Sciences'', 2 (6) : 441-502 ; see especially pp. 473-477. * Charles Webster (1963) "Richard Towneley and Boyle's Law," ''Nature'', 197 (4864) : 226-228. * Robert Boyle acknowledged his debts to Towneley and Power in: R. Boyle, ''A Defence of the Doctrine Touching the Spring and Weight of the Air,'' … (London, England: Thomas Robinson, 1662) Available on-line at: ( Spain's La Biblioteca Virtual de Patrimonio Bibliográfico ). On pages 50, 55-56, and 64, Boyle cited experiments by Towneley and Power showing that air expands as the ambient pressure decreases. On p. 63, Boyle acknowledged Towneley's help in interpreting Boyle's data from experiments relating the pressure to the volume of a quantity of air. (Also, on p. 64, Boyle acknowledged that Lord Brouncker had also investigated the same subject.)〕 Robert Boyle confirmed their discovery through experiments and published the results.〔R. Boyle, ''A Defence of the Doctrine Touching the Spring and Weight of the Air,'' … (London, England: Thomas Robinson, 1662) Available on-line at: ( Spain's La Biblioteca Virtual de Patrimonio Bibliográfico ). Boyle presents his law in "Chap. V. Two new experiments touching the measure of the force of the spring of air compress'd and dilated.", pp. 57-68. On p. 59, Boyle concludes that " … the same air being brought to a degree of density about twice as that it had before, obtains a spring twice as strong as formerly." That is, doubling the density of a quantity of air doubles its pressure. Since air's density is proportional to its pressure, then for a fixed quantity of air, the product of its pressure and its volume is constant. On page 60, he presents his data on the compression of air: "A Table of the Condensation of the Air." The legend (p. 60) accompanying the table states: "E. What the pressure should be according to the ''Hypothesis'', that supposes the pressures and expansions to be in reciprocal relation." On p. 64, Boyle presents his data on the expansion of air: "A Table of the Rarefaction of the Air."〕 According to Robert Gunther and other authorities, it was Boyle's assistant, Robert Hooke, who built the experimental apparatus. Boyle's law is based on experiments with air, which he considered to be a fluid of particles at rest in between small invisible springs. At that time, air was still seen as one of the four elements, but Boyle disagreed. Boyle's interest was probably to understand air as an essential element of life;〔The Boyle Papers BP 9, fol. 75v-76r at (BBK.ac.uk )〕 for example, he published works on the growth of plants without air.〔The Boyle Papers, BP 10, fol. 138v-139r at (BBK.ac.uk )〕 Boyle used a closed J-shaped tube and after pouring mercury from one side he forced the air on the other side to contract under the pressure of mercury. After repeating the experiment several times and using different amounts of mercury he found that under controlled conditions, the pressure of a gas is inversely proportional to the volume occupied by it. The French physicist Edme Mariotte (1620–1684) discovered the same law independent of Boyle in 1679,〔See: * Mariotte, ''Essais de Physique, ou mémoires pour servir à la science des choses naturelles,'' … (Paris, France: E. Michallet, 1679); "Second essai. De la nature de l'air". * (Mariotte, Edmé), ''Oeuvres de Mr. Mariotte, de l'Académie royale des sciences;'' … , vol. 1 (Leiden, Nethelands: P. Vander Aa, 1717); see especially (pp. 151-153. ) * Mariotte's essay ''"De la nature de l'air"'' was reviewed by the French Royal Academy of Sciences in 1679. See: (Anon.) (1733) ("Sur la nature de l'air," ) ''Histoire de l'Académie Royale des Sciences'', 1 : 270-278. * Mariotte's essay ''"De la nature de l'air"'' was also reviewed in the ''Journal des Sçavans'' (later: ''Journal des Savants'') on 20 November 1679. See: (Anon.) (20 November 1679) ("Essais de physique, … ," ) ''Journal des Sçavans'', pp. 265-269.〕 but Boyle had already published it in 1662. Thus this law is sometimes referred to as Mariotte's law or the Boyle–Mariotte law. Later, in 1687 in the Philosophiæ Naturalis Principia Mathematica, Newton showed mathematically that if an elastic fluid consisting of particles at rest, between which are repulsive forces inversely proportional to their distance, the density would be directly proportional to the pressure,〔Principia, Sec.V,prop. XXI, Theorem XVI〕 but this mathematical treatise is not the physical explanation for the observed relationship. Instead of a static theory a kinetic theory is needed, which was provided two centuries later by Maxwell and Boltzmann. This law was the first physical law to be expressed in the form of an equation describing the dependence of two variable quantities. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Boyle's law」の詳細全文を読む スポンサード リンク
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