Background
Émile Hilaire Amagat was born on January 2, 1841, in Saint-Satur, France.
Émile Hilaire Amagat was born on January 2, 1841, in Saint-Satur, France.
Amagat obtained his doctorate in 1872 from Paris.
Amagat became docleur-es-sciences at Paris in February 1872 and was then, successively, agrégé, professor of physics at the Faculté Libre des Sciences of Lyons, and examiner at the École Polytechnique. He was elected a corresponding member of the Académie des Sciences on 5 May 1890, received from the Institut the Prix Lacaze pour la Physique in 1893, and became a full member of the Académie on 9 June 1902.
Amagat’s work dealt with fluid statics. At the time he began his work, Andrews had just announced the structure of a few isotherms of carbon dioxide at between 10°and 50°C and up to 110 atmospheres, the region in which the product of pressure times volume is at a minimum for this compound. Andrews’ report was published in France in 1870, and his research was the only one, at the time, to use varying temperatures. From 1869 to 1872 Amagat studied the effect of temperatures up to 320° on the compressibility and expansion of gases. These studies led to his doctoral thesis.
Knowledge of liquids was even more limited. It was known that, except for water, the coefficient of compressibility increases with the temperature. Amagat published an extensive report on this subject in 1877, showing that this coefficient clearly decreases when pressure increases, which was contrary to the results reached by other experimenters.
There remained the search for the laws of the coefficients of compressibility, the coefficients of expansion under constant pressure and constant volume, the coefficients of pressure when both pressure and temperature are varied, and the limits toward which these laws tend when matter is more and more condensed by pressure. It was to this research that Amagat devoted the active phase of his career.
His first works were published between 1879 and 1882. They display the isotherms of a number of gases for temperatures between 0° and 100° and for pressures up to slightly more than 400 atmospheres (the limit that could be borne by the sturdiest glass tubes available).
The experimental data used as a base for this research were furnished by measurements taken in 1879 in a mine shaft at Verpilleux, near Saint-Étienne. Amagat determined by means of a column of mercury 327 meters high the compressibility of nitrogen up to 430 atmospheres. His results were universally adopted for the calculation of gas manometers. Until then only Regnault’s results had been available, and they went only to thirty atmospheres. As for Andrews, he had been content to apply Mariotte’s (Boyle’s) law up to 110 atmospheres, using a compressed-air manometer.
At the end of this first stage of his research Amagat realized that certain questions vital to the theory of fluids could be elucidated only by greatly increasing the limit of pressures. But having already gone beyond the possible resistance of glass tubes, he had to invent new experimental methods. At this point Amagat created his most ingenious apparatus, the manometer with free-moving pistons in viscous liquids; thus he was able to measure with certainty and regularity pressures above 3,000 atmospheres. Using an idea that originated with Gally-Cazolat, Amagat constructed an apparatus that was a back-acting hydraulic press made gas-tight by means of a viscous liquid such as molasses or castor oil.
Having been forced to study the elasticity of glass in order to gauge the variations in volume of the containers holding the fluids studied, in 1889-1890 Amagat broadened his study until it embraced the elasticity of solids in general, starting with a verification of the general formulas of elasticity. As a correlative study he had to determine the compressibility of mercury. As early as 1876 and 1882 he had done research on the elasticity of rarefied gases. Amagat found that air, hydrogen, and carbon dioxide follow Mariotte’s law at pressures as low as 1/10,000 atmosphere.
Amagat held various special studies related to his general research of fluid statics: interior pressure of fluids; negative interior pressure; laws regulating the specific heats of fluids at different temperatures and pressures, and their relationship; verification of Van Der Waals’ law of corresponding states, according to which the equation of the state of all gases can be represented by a single function in which critical temperature, pressure, and volume appear as parameters; solidification of liquids by pressure; determination of the density of liquefied gases and of their saturated vapor; the atomic volume of oxygen and of hydrogen; the interaction of oxygen and mercury; the differential equation of the speed of sound in gases; and the relations between the coefficients of the formulas of Coulomb (magnetism), Laplace, and Ampère: “The Laplace formula connects those of Coulomb and of Ampère but only by employing an almost constant factor that experience alone can determine.”