JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. II, JUNE 4, 1912 No. 11 



ELECTRICITY.— Work of the International Technical Com- 

 mittee on Electrical Units. E. B. Rosa and F. A. Wolff. 



The International Electrical Conference at London in 1908 

 adopted specifications for the mercury ohm, the silver voltameter 

 and the Weston Normal Cell, and fixed a provisional value 

 (1.0184 international volts at 20°C.) for the last. The specifica- 

 tions for the mercury ohm and the Weston cell were more or less 

 complete, but for the silver voltameter the specifications were 

 very inadequate, and since the value to be assigned to the Weston 

 cell necessarily depends upon the specifications for the silver 

 voltameter, and the results of different investigators were not 

 in close agreement, the conference selected an approximate value 

 which it adopted as provisional only, until further experiments 

 could be made and more precise values determined. 



The Weston normal cell, officially adopted at the London 

 Conference in place of the Clark cell, has had the following values: 

 In America, 1.0189 at 25°, equivalent to 1.0191 volts at 20°; in 

 Germany, 1.0186 volts at 20°; in England, 1.0184 volts at 20°. 

 Some of the other countries have the same value as America, 

 others the same as Germany. 



In order that the different countries might cooperate in fixing 

 and maintaining uniform throughout the world the values of 

 the electrical units, the London Conference established an Inter- 

 national Committee on Electrical Units and Standards, charged 

 with the duty of promoting investigations in electrical standards 

 and electrical measurements, and of securing the intercompari- 

 son of the standards of different countries. This committee 

 represents eleven different countries, there being two members 

 each from America, England, France and Germany, and one 



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