Mitscherlich in 1820; and he confirmed his conclusions by showing the agreement with the law of atomic heat formulated by Dulong and Petit in 1819.
Rose; liquid phosphuretted hydrogen was first obtained by Thenard in 1838; and hypophosphorous acid was discovered by Dulong in 1816.
Dulong to investigate relations (if any) existing between specific heats and the atomic weight.
Their observations on the solid elements led to a remarkable generalization, now known as Dulong and Petit's law.
The value of this constant when 11= i is about 6.4; Dulong and Petit, using 0=1, gave the value.
It is apparent that the law of Dulong and Petit is not rigorously true, and that deviations are observed which invalidate the law as originally framed.
Deductions from Dulong and Petit's Law.
- Denoting the atomic weight by W and the specific heat by s, Dulong and Petit's law states that 6.4 = Ws.
Dulong and Petit's law thus points to the value 114, which is also supported by the position occupied by this element in the periodic classification.
Dulong in 1811 (Schweigg.
Its specific gravity has the high value 18.7; its specific heat is 0.02765, which, according to Dulong and Petit's law, corresponds to U = 240: It melts at bright redness.
The general result is that, conformably with Dulong and Petit's law, the "atomic heats" all come to very nearly the same value (of about 6.4); i.e.
In later years Berzelius renounced the " oxygen acid " theory, but not before Davy, and, almost simultaneously, Dulong, had submitted that hydrogen and not oxygen was the acidifying principle.
Its specific heat is between 0.0298 (Dulong and Petit) and 0.03244 (Regnault).
From Dulong and Petit's law that Cm is the same for all elements, it follows that n+3 must be the same for all atoms. Moreover, the value of Cm shows that n+3 must be equal to six.
Dulong, his old master, and in many respects his model.
Considering The Wide Variations In The Physical Condition And Melting Points, The Comparatively Close Agreement Of The Atomic Heats Of The Metals At Ordinary Temperatures, Known As Dulong And Petit'S Law, Is Very Remarkable.
PIERRE LOUIS DULONG (1785-1838), French chemist and physicist, was born at Rouen on the 12th (or 13th) of February 1785.
In a third, " On some important points in the theory of heat " (1819), they stated that the specific heats of thirteen solid elements which they had investigated were nearly proportional to their atomic weights - a fact otherwise expressed in the " law of Dulong and Petit " that the atoms of simple substances have equal capacities for heat.
Subsequent papers by Dulong were concerned with " New determinations of the proportions of water and the density of certain elastic fluids " (1820, with Berzelius); the property possessed by certain metals of facilitating the combination of gases (1823 with Thenard); the refracting powers of gases (1826); and the specific heats of gases (1829).
The original intention was to push the experiments to a pressure equivalent to thirty atmospheres, but owing to the signs of failure exhibited by the boiler the limit actually reached was twenty-four atmospheres, at which pressure the thermometers indicated a temperature of about 224 0 C. In his last paper, published posthumously in 1838, Dulong gave an account of experiments made to determine the heat disengaged in the combination of various simple and compound bodies, together with a description of the calorimeter he employed.
Dulong, but was obliged to suspend his inquiries during the winter on account of injury to his eye caused by an explosion of that substance.
Hypophosphorous acid, HP(OH) 2, discovered by Dulong in 1816, and obtained crystalline by Thomson in 1874 (Ber., 7, P. 994), is prepared in the form of its barium salt by warming phosphorus with baryta water, removing the excess of baryta by carbon dioxide, and crystallizing the filtrate.
Phosphorus pentachloride, PC15, discovered by Davy in 1810 and analysed by Dulong in 1816, is formed from chlorine and the trichloride.