290 



Hartley — The Action of Heat on the Absorption Spectra and 



Didymium Potassium Nitrate.- 



From 30° to 60°. 

 Spectrum begins with a weak band at X 594. 

 A feeble absorption extends from 594 to 588. 

 Absorption Band — 



588 to 581 

 Absorption Band — 



533 to 530 

 Absorption Band — 

 523 to 521 

 Narrow Absorption Bands or lines — 

 488 

 478 

 Absorption Band — 

 454 to 449 



-Thick wedge-cell, sunlight. 



At 100°. 



Spectrum begins with a dark band at A 600. 



Absorjition Band — 



600 to 581. Feeble, narrow. 



Absorption Band or line — 



543 



Absorption Band — 



534 to 530 

 Absorption Band — 

 523 to 521 

 Absorption Bands or lines — 

 488 

 478 

 Absorption Band — 

 454 to 449 



The measurement of the decided black band in the red was at 588 on the side 

 of least refrangibility, and a faint shade extended farther in this direction to 594. 

 On heating the solution the band thickened out to 600. In the thin wedge-cell 

 the following measurements were the only ones possible : — 



At 20°. 

 At 100°, 



The narrow band at 455 was described in the note-book as a faint shade. 



It will be seen that the principal band, which widens out from 630 to 581 when 

 the solution is heated in the thick cell, here remains quite unchanged at 100°. 

 The measurement at 543 is a feeble band like a line, not visible in the cold solution. 



It may be mentioned that, at 588 and 581, the bands belonging to praseodym 



and neodym meet. The bands at 488 and 454 to 449 are probably due to 



erbium . 



Didymium Acetate. — Thin wedge-cell. 



At 20°. 

 Rays visible at 706. 



Absorption Ba7ids — 



Red 685 to 673 



Orange, . . . 



Greeti, . 



. 588 to 572 



( 533 to 529 



• 1522 to 519 



Blue, .... (491 to 488 

 1,481 to 478 

 Edge of a band at 476. 

 Edge of a band, 466. 



Broad Absorption Band — 

 Blue,* . . . . 453 to 448 

 A dark line, 456. 



* Probably an erbium band 



At 100°. 



Absorption Bands — 



704 to 627 



598 to 577 



Beyond this all was obscured. 



