AS AFFECTED BY TEMPERATURE. 15 



and 185. The part of the spectrogram above X4550 was exposed 40 seconds, 

 while below that wave-length the exposure was 10 minutes. The apparent 

 band extending entirely across the spectrogram near X4550 is the edge of the 

 screen used in making the long exposure on the violet end of the spectrogram 

 and must not be confused with an absorption band. 



Absorption bands X4175 and X4325 have their centers shifted towards the 

 red end of the spectrum about 25 a.u. The red edges of bands X4325 and 

 X4550 shade rapidly towards the red. The well-marked band X4750 remains 

 unchanged throughout the spectrogram. 



The encroachment of the general absorption in the ultra-violet towards 

 the red causes band X3625 to disappear above the fourth strip, while band 

 X3750 is scarcely visible above strip 5. All bands below X4500 become very 

 diffuse as the temperature is raised, and at the highest temperature are 

 hardly more than a single broad, hazy absorption band extending from 

 X4000 to X4400. 



Section B is the spectrum of a 0.02 normal solution of uranyl sulphate, 

 the depth of absorbing layer being 10 cm. The respective temperatures, 

 beginning with the strip nearest the numbered scale, were 20, 45, 70, 95, 

 1 15, 140, and 165. The exposures were 8 seconds in the visible part of the 

 spectrum and an additional exposure of 4 minutes to the ultra-violet. The 

 same changes described in A take place here, i. e., a strong general absorp- 

 tion in the ultra-violet beyond X3500, and increasing towards the red as the 

 temperature is raised. The most marked widening is in bands X4100, 

 X4200 and X4350; in each the center shifted slightly towards the red. Such 

 is also the case with the red edge of band X4600. The X4750 band remains 

 fixed throughout the spectrogram. The very broad, hazy bands around 

 X5100, X5600, and X6200 appear, and are not appreciably affected by changes 

 in temperature. 



URANYL ACETATE IN WATER. (See Plate 12.) 



In plate 12, A shows the effect of dilution, B of temperature. The con- 

 centrations of the solutions used in A, beginning with the strip farthest 

 removed from the numbered scale, were 0.25, 0.125, 0.062, 0.042, 0.0025, 

 and 0.0005 normal. So far as we can judge from this plate, none of the 

 absorption bands changes. Beer's law seems to hold to the dilution 0.0005 

 normal. 



B shows the effect of rise in temperature on a 0.02 normal solution of 

 uranyl acetate. The temperatures, beginning with the strip nearest the 

 numbered scale, were 20, 45, 70, 95, 115, and 140. The exposures at 

 that part of the spectrum having a wave-length greater than X4500 was 8 

 seconds, while an additional exposure of 3 minutes was given to the ultra- 

 violet end. Every one of the nine bands shows a slight widening with rise in 

 temperature. While in strip 1 the bands are well marked, they appear 

 much more diffuse as the temperature is raised. The apparent change in 

 the band near X4475 is probably due to the screen used to cut off the visible 

 spectrum, while additional exposure was made to the ultra-violet region. 



