Notices of the proceedings at the meetings of the members of the Royal Institution of Great Britain with abstracts of the discourses . ond and graphite, and ice. A large series of observations were made upon carbon in both itsforms, the ranges of temperature being from about 18° 0. to theboiling point of carbonic acid, thence to the boiling point of oxygen, 1004.] on Liquid Hydrogen Colorimetry. 591 and finally to the boiling point of hydrogen. Early determinationsof the specific heat of carbon in any of its forms had shown completedeparture from the law of Dulong and Petit. In 1872 ProfessorH
Notices of the proceedings at the meetings of the members of the Royal Institution of Great Britain with abstracts of the discourses . ond and graphite, and ice. A large series of observations were made upon carbon in both itsforms, the ranges of temperature being from about 18° 0. to theboiling point of carbonic acid, thence to the boiling point of oxygen, 1004.] on Liquid Hydrogen Colorimetry. 591 and finally to the boiling point of hydrogen. Early determinationsof the specific heat of carbon in any of its forms had shown completedeparture from the law of Dulong and Petit. In 1872 ProfessorH. P. Weber and myself,* working independently, found that, as thetemperature increased, the specific heat of carbon, whether as diamondor as graphite, continued to increase. Professor Weber found thatthe specific heat of the diamond is tripled when the temperature israised from 0° to 200°, and my experiments showed that the meanspecific heat of carbon from 30° to the boiling point of zinc waso • :52, and to the temperature of the oxy-hydrogen blow-pipe (some1*000° C.) it rose to 0*42, and I added the true specific heat at. 2000° must be at least 0*5; so that at this temperature carbonwould agree with the law of Dulong and Petit. In 1875 f ProfessorWeber published the results of further experiments, proceeding bysuccessive stages up to 1000° C, and showing that from the point(about 600°) at which the specific heat of carbon ceases to varywith increase of temperature, and becomes comparable with that ofother elements, any real difference in the specific heats of the twomodifications disappears, and carbon obevs the law of Dulong andPetit. Professor Weber plotted his results, taking specific heat as theordinate, to temperature as the abscissa, and producing a curve likethe old English / He found the poinc of inflection for diamond * H. F. Weber, The Specific Heat of Carbon, Phil. Mag. 1872, ser. 4,toI. xliv., p. 251. J. Dewar, The Specific Heat of Carbon at High Tempera-
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