The Value of the Silver Oun. 



301 



of the groove-form on the spectral intensity in the theory of 

 gratings. 



The experimental work forming- the suhject of this paper 

 was carried out in the Palit Laboratory of Physics. The 

 author's best thanks are due to Prof. 0. V. Raman, who made 

 some preliminary observations on the large-angle diffraction 

 by an elliptic aperture, and at whose suggestion the present 

 investigation was undertaken. 



Calcutta, 

 14th February. 1919. 



XXV II. The Value of the Silver Oun. 

 By W. M. Hicks, F.B.S.* 



Data from [IV. p. 3(54] of link values for silver. 



a 



880-77. 



e 3771-00. 



b 



920-44. 



u 2458-64. 



c 



962-54. 



v 2616-61. 



d 



1007-26. 





I HAVE proposed f the name of oun for that quantity, 

 proportional to the square of the atomic weight, on which 

 the separations of doublets and triplets and of satellites in 

 series spectra as well as the constitution of the d and / 

 sequences depend. The determination of the exact ratio of 

 the oun to the square of the atomic weight is a question of 

 some importance, but it involves not only a knowledge of 

 the exact value of the oun for a given element, but also 

 of the exact weight. If the atomic weight of Ag (107-880) 

 is regarded as the basis of the table of weights for other 

 elements, no uncertainty arises in the latter respect. The 

 ratio for Ag will serve for all elements if their atomic weights 

 are correctly measured in terms of Ag = 107'880. At least 

 this will be so if the ratio is the same for all elements. To 

 four significant figures the ratio is certainly the same. 

 Whether the equality is exact to a higher degree must be a 

 matter for future investigation. The determination of the 

 ratio for silver to six significant figures will be a first step in 

 this investigation. The present note is an attempt to deter- 

 mine this to within three units in the sixth place or say 1 in 

 100,000. An attempt to do this was made in the Transactions 

 paper above referred to (p. 403), but a difficulty arose 



* Communicated bv the Author. 



t Phil. Trans. A. 213. p. 33l> (1913). 



Phil. Mag. S. 6. Vol. 38. No. 22Z. Sept. J 919. Y 



