Theoretical chemistry from the standpoint of Avogadro's rule & thermodynamics / [Walther Nernst].

  • Walther Nernst
Date:
1911
Catalogue details

Licence: In copyright

Credit: Theoretical chemistry from the standpoint of Avogadro's rule & thermodynamics / [Walther Nernst]. Source: Wellcome Collection.

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    calorimeter; in the fifth those of Dieterici,1 obtained by the use of an ice calorimeter. I. II. III. IV. V. 0° 1-0080 1-0051 1-0080 1-0088 5° 1-0054 1-0046 1-0027 1-0050 1-0050 10° 1-0019 1-0018 1-0010 1-0020 1-0021 15° 1-0000 1-0000 1-0000 1-0000 1-0000 20° 0-9979 0-9994 0-9994 0-9986 0-9987 25° 0-9972 0-9997 0-9993 [0-9977 0-9983 30° 0-9969 1-0000 0-9996 0-9972 0-9984 35° 0-9981 ... 1-0003 0-9971 0-9985 The zero-calorie.is POOS times the usual calorie; the value of the mean calorie is 1'005 according to Lfidin, 1'0013 according to Dieterici, and 0-9997 according to Behn.2 For the mechanical equivalent of the usual calorie at latitude 45, Pernet (l.c.) reckons 42,555 gram centimetres from the experiments of Joule, 42,547 from Rowland, and 42,637 from Miculescu; E. .H. Griffiths, on the one hand, Schuster and Gannon on the other, found by measurements of electrically developed heat practically the same value, 42,730 ; as the most probable value we shall adopt 42,72 0, following the example of Warburg,3 and Waidner and Mallory.4 The meaning of this number is that if in latitude 45° a gram be allowed to fall through 42,720 centimetres the kinetic energy acquired converted into heat would suffice to raise the temperature of a gram of water at 15° by 1° on the air thermometer scale. In the absolute system of measurement the value of the ordinary calorie is 42,720 x 980-6 = 41,890,000 ergs. (980-6 = acceleration of gravity in latitude 45°), or 41 89 million ergs. = 4‘189 Joules. Sometimes the kilogram-calorie, which is 1000 times the gram- calorie, is used instead of the latter : its mechanical equivalent is 427 metre kilograms. The two units are distinguished by the names “ large ” and “small calorie” respectively; in the following the foimei will be denoted Cal., the latter cal. Very often, and in calculations which are of especial importance foi the chemist, the problem is given to express, in units of heat, the work performed in overcoming the pressure on a definite volume. . F oi example, in a cylinder with a movable piston of a cross-section of 1 sq. dcm., on which the atmosphere presses with a pressure of one 1 Ann. d. Pliys. [4], 16. 593 (1905). 2 Ann. d. Phys. [4], 10. 653 (1905). 3 See Die Wdrmeeinheit. Leipzig, 1900 (Barth). 4 Zeitschr. f. Instrumentenkunde, 1900, p. 59 ; Phys. Rev. 8. 193 (189 ).