Table 293. 



261 



ABSOLUTE MEASUREMENTS OF CURRENTS AND OF THE ELECTRO- 

 MOTIVE FORCE OF STANDARD CELLS. 



Date. 



1872 



1873 

 1882 

 1884 

 1884 

 1886 

 1887 

 1890 

 1896 

 1898 

 1899 

 1902 

 1903 

 1904 

 190s 

 1906 

 1907 

 1907 

 1908 

 1908 

 1908 

 1908 

 1910 

 1911 

 1911 

 1913 



Observer. 



Clark 



F. Kohlrausch 



F. and W. Kohlrausch 



Rayleigh and Sedgwick 



Gray 



Koepsel 



Potier and Pellat 



Kahle t 



Patterson and Guthe 



Carhart and Guthe 



Callendar and King 



Pellat and Leduc 



Van Dijk and Kunst 



Guthe 



Van Dijk 



Ayrton, Mather and Smith 



Smith, Mather and Lowry 



Janet, Laporte and Jouaust J 



Janet, Laporte and de la Gorce 



Guillet t 



Pellat t 



Haga and Boerema 



Rosa, Dorsey and Miller 



Rosa, Vinal and McDaniel 



Haga and Boerema 



Method. 



{Electrodynamometer 

 Sine Galvanometer 

 Tangent Galvanometer 

 Current Balance 

 Tangent Galvanometer 

 Current Balance 

 Sine Galvanometer 

 Electromag. Balance 

 Electrodynamometer 

 Electrodynamometer 

 Electrodynamometer 

 Electrodynamometer 

 Electrodynamometer 

 Electrodynamometer 

 Tangent Galvanometer 

 Electrodynamometer 

 Revision of 1904 work 

 Current Balance 

 With the above 

 Current Balance 

 With the above 

 Current Balance 

 Electrodynamometer 

 Tangent Galvanometer 

 Current Balance 

 With the above 

 Tangent Galvanometer 



Electromotive 

 Force* of 



Clark 

 Cell at 

 15° C. 



Weston 

 Cell at 

 20° C. 



Volts. 



1-4573 

 1.4562 



1-4333 

 1-4334 



Volts. 



.0183 



1.43296 I 

 1.4323 



01853 



r.01819 



:.oi836 



1.01812 

 t.01831 

 [.0182s 

 1.01822 



Electrochemical Equiv- 

 alent of Silver. 



Filter 

 Paper 

 Volta- 

 meter. 



Mg. 



1. 1363 



111794 



1.11740 



1.1195 

 1.11823 



1.11827 

 1. 11821 



Porous 

 Cup 

 Volta- 

 meter. 



Mg. 



.11773 

 .1180 



1. 11804 



No- 

 Septum 

 Volta- 

 meter. 



Mg. 



1.1156 

 1.1183 



1.1183 



1.1192 



1.11S3 



1.11804 

 1. 11802 



1 Proc. Roy. Soc. May 30th, 1872 (Values in B. A. volts 



atis.sC). 



2 Pogg. Ann. vol. 149, p. 170 (anode wrapped in cloth). 



3 J. de Phys. vol. 1, p. 109, vol. 3, p. 283. 



4 Wied. Ann. vol. 27, p. i, 1886. 



5 Phil. Trans. A, vol. 175, p. 411, 1884. 



6 Phil. Mag. vol. 22, p. 389, 1886. 



7 Ann. d. Phys. vol. 31, p. 250, 1887. 



8 J. de Phys. vol. 9, p. 381, 1890. 



9 Zs f Instr. vol. 17, p. 97, 143-4, vol. 18, p. 276. 



10 Phys. Rev. vol. 7, p. 257. (Added Ag2o). 



11 Phys. Rev. vol. 9, p. 288, 1899. 



12 Phil. Trans. A, vol. 199, p. 81, 1902. 



13 C. R. vol. 136, p. 1649. (Muslin and filter paper both 



used .) 



14 Ann. d. Phys. vol. 14, p. 569, 1904. 



15 Bull. B. S. vol. 2, p. 33, 1906. 



16 Ann. d. Phys. vol. 19, p. 249, 1906. 



17 Phil. Trans. A, vol, 207, p. 463, 1908. 



18 Phil. Trans. A, vol. 207, p. 545, 1908. 



19 Bull. Int. Soc. Electr. vol. 8, p. 459, 1908. C. R. vol 



153, p. 718, 1911. 



20 Bull. Int. Soc. Electr. vol. 8, p. 523, 1908. 



21 Bull. Int. Soc. Electr. vol. 8, p. 535, 1908. 



22 Bull. Int. Soc. Electr. vol. 8, p. 573, 1908. 



23 Proc. Ak. Wiss. Amster. vol. 13, p. 587. 



24 Bull. Bureau Standards, vol. 8, p. 269, 1912. 



25 Bull. Bulletin Standards, vol. 8, p. 367, 1912. 



26 Arch. Neer. Sci. IIIA, vol. 3, p. 324, 1913- 



* The values given in these columns are not strictly absolute volts since they were in most cases determined in terms 

 of an absolute ampere and an international ohm. Hence they may be called "semi-absolute." No absolute determina- 

 tions of the ohm have been made in recent times, but some are in progress. 



t Other values usually given as Kahle's results and ofincially used by the Reichsanstalt are voltameter determinations. 

 To include them here would necessitate including many others similarly made. The value 1.1183 includes s filter paper 

 determinations out of 26 observations. 



t These values have been corrected for the difference between the French ohm at this time and that in use elsewhere. 

 (C. R. vol. IS3, p. 718.) 



Measurements prior to Van Dijk ( 1906) and the subsequent filter paper voltameter determinations are now only of 

 historical interest, but the large amount of work done in recent years makes these early determinations of especial inter- 

 est. The errors due to the use of filter paper and other impurities (acid, alkali, colloidal matter, etc.) in the voltameter 

 electrolyte make it impossible to apply corrections. The values for the cell are not readily comparable owing to varia- 

 tions in the voltage of the cell itself and the unit of resistance. See Dorn, Wiss. Abhl. der Phys. Tech. Reich., vol. II, p. 

 2S7. Since 1911 the voltage adopted for the Weston Normal Cell at 20° C. is 1.0183 international volts in all the leading 

 countries. The international volt is to be distinguished from the absolute volt since it is based on the definition of the 

 mercury ohm and the silver voltameter, taking the electrochemical equivalent of silver to be i.n8oo mg per coulomb. 

 The difference between the international volt and the absolute volt is negligible for practical purposes. The tempera- 

 ture coefficient of the W'eston Normal Cell (saturated type) is given in Table 294. The new value of the Weston cell was 

 adopted in the United States on January i, igii. 



Smithsonian Tables. 



