PRASEODYMIUM SALTS. 67 



ampere and slit-width 0.20 mm.) for 20 seconds. The length of exposure 

 to the spark was 4 minutes. Starting with the strip nearest the compari- 

 son scale, the temperatures were 6, 19, 47, 70 and 90. 



On account of the great concentration and the depth of cell, the absorp- 

 tion bands are very wide. The whole ultra-violet portion of the spectrum 

 is absorbed up to X 3550. Rise in temperature does not cause any change 

 in this absorption. The band in the blue extends from X 4300 to X 4940 at 

 6. A weak and rather broad band appears at X 5120 and a narrow band at 

 X 5240, this band being about 15 Angstrom units wide. The yellow band 

 extends from X 5760 to X 6120 at 6. 



As the temperature rises the blue and yellow bands gradually widen. 

 At 47 the blue band extends from X 4290 to X 4950, the yellow band from 

 X 5750 to X 6120. At 90 the violet band was bounded by XX 4280 and 4960, 

 the yellow band by XX 5740 and 6140. At 70 the ballast burned and the 

 exposure to the Nernst glower was not quite as long as it should have been. 



The bands M 5120 and 5240 appeared very slightly affected by the rise 

 in temperature here used. The violet and yellow bands broadened very 

 slightly and symmetrically with rise in temperature. 



Plate 33, A, represents the absorption spectra of a 2.6 normal solution 

 of praseodymium nitrate 3 mm. deep. Starting with the strip nearest the 

 numbered scale, the temperatures are 6, 16, 34, 46, 58, 70, and 82. 



The four characteristic wide absorption bands appear very slightly 

 affected by rise in temperature. The NO s band in the ultra-violet widens 

 slightly. 



