52 



:^OSA, VINAL, AND McDANIEL : SILVER VOLTAMETER 



expressing the corrections in the table. A piece of co-ordinate 

 paper cut diagonally at the proper angle forms a convenient scale. 

 The corrections at the beginning of each turn are measured by the 

 distances between the curve of progressive corrections and the 

 inclined line correcting for magnification. The corrections at the 



tenths of a turn are read from the corresponding curves, the base 

 line of each being shifted if necessary to correct for magnifica- 

 tion within a turn. (Progressive errors within a turn as well as 

 periodic errors were cared for in deriving the curves.) These 

 internal corrections must, of course, be added to the correction at 

 the beginning of the turn before entering in the table. 



ELECTROCHEMISTRY.— r/ie silver voltameter. Part IV. E. 

 B. Rosa, G. W. Vinal, and A. S. McDaniel. To appear in 

 full in the Bulletin of the Bureau of Standards. 



In the three papers preceding this, the course of the work has 

 been traced from its beginning in 1908 until the International 

 Technical Committee met in Washington in April, 1910, to carry 

 out a joint investigation of the voltameter and to determine the 

 voltage of the Weston Normal Cell in terms of the international 

 ohm and the international ampere, the latter being derived from 

 the silver voltameter. The object of the present work is to make 

 a further comparison of the porous cup and Smith forms of volta- 

 meter, since these have been found the most reliable forms dur- 



