1080 Mr. D. Coster on the Specfra of X-rays 



was used. On the other hand, the high tension gave some 

 trouble in identifying the lines, as several lines due to other 

 elements appeared in higher orders on the plates (e.g., on " 

 many plates taken with a gypsum crystal, Cu K-lines and 

 W L-lines were obtained in as high as the 5th order) . In 

 general, the best plates were obtained when the element 

 could be placed in the form of a metallic sheet on the anti- 

 cathode. For this reason Sb, Sn, In, and Cd were melted 

 in a fairly pure state on the copper auticathode, while the 

 elements Ag, Pd, and Rh were attached with solder ; Mo was 

 pressed in a copper ring which was soldered on to the anti- 

 cathode. There was no particular difficulty in obtaining 

 good plates with these elements. 



The other elements examined on this occasion (i. e., Ba, 

 Cs, Te, Ru, Nb, Zr, Y, Sr, and Rb) were used in the form of 

 salts or oxides, which were pressed into the roughened 

 surface of a copper plate soldered on to the anticathode. 

 For every element this copper plate was renewed. As the 

 salts are sputtered from the anticathode somewhat quickly, 

 it appeared to be better not to use the highest energy which 

 could be obtained from the apparatus. In general, for these 

 elements the best plates were obtained with a maximum 

 tension of about 20-25 k.v. and a current of: not more than 

 15 m.a. For each element from 6 to 10 different plates 

 were taken through the whole region of the spectrum. 

 Between two exposures the tube was opened and a fresh 

 quantity of salt was brought on the anticathode. Very often 

 it was necessary to take several plates of the same part of 

 the spectrum before a good one was obtained. 



§4. The distances of the lines on the plates were meas- 

 ured under the microscope, and from this the wave-lengths of 

 the new lines could be measured relatively to the lines « 1? /3 1? 

 and y l which have previously been determined with great pre- 

 cision by Hjalmar *. The other lines mentioned by Hjalmar 

 (« 2 , « 3 , # 4 , /3 3 , /3 2 , and in a few cases 72, 73, 7J were usually 

 determined by this author either relatively to « 1? /3\, 71, or 

 from the old measurements of Friman, a correction having 

 been applied. 



In the following tables the lines determined by Hjalmar 

 by the precision method as well as those measured relatively 

 to them on his own plates have been taken from this author 

 without change. These comprise nearly all the lines whose 

 wave-lengths appear in his tables to one or two decimal 

 places. The other lines have been determined in the present 

 investigation. 



* Zeitschr.f. Physik, iii. p. 262 (1920), and vii. p. 341 (1921). 



