96 



A STUDY OF THE ABSORPTION SPECTRA. 



The most important effect of the addition of water is the reducing of 

 the intensity and changing the position of the uranyl chloride bands. In A, 

 the bands a and b appear in the pure alcoholic solution. The b band is 

 very intense. As the amount of water is increased a disappears, only one 

 edge of it being recognizable in a 16 per cent aqueous solution, b is greatly 

 reduced in intensity and is shifted towards the violet by the addition of 

 water. B shows still better this effect upon the uranyl bands. In the 

 alcoholic solution the bands a, b, c, f, g, h, and i appear. In the 8 per cent 

 aqueous solution b, c, d, e, f, g, h, i, j; in the 16 per cent aqueous solution 

 b, c, d, e, f, g, h, i, and j; in the 24 per cent aqueous solution the bands 

 are much weaker and in the strips showing a greater amount of water than 

 this, practically only b and c are visible and these two bands are extremely 

 faint. The greatest effect appears before the amount of water is greater 

 than 20 per cent. The general effect upon the position of the uranyl bands 

 is quite remarkable the b and c bands are shifted towards the violet with 

 increase of water, whereas the ultra-violet bands appear to be shifted 

 towards the red. 



Uranyl chloride in 



Water 



CH 4 



CaCl 2 \ 



CH 4 / 



C,H 6 



Water and A1C1, 



4010 



3980 3860 

 4010 



Uranyl Chloride in Ethyl Alcohol. 



Plate 58, B, represents the absorption spectra of an ethyl alcohol solu- 

 tion of uranyl chloride, the depth of cell being kept constant 6 mm. and 

 the concentration varied. Starting with the upper strip the concentrations 

 were 0.25, 0.2, 0.158, 0.125, 0.1, 0.079, and 0.0625 normal. The strips 

 were each exposed 1 minute to the Nernst glower, slit-width being 0.08 

 mm., current 0.8 ampere. A comparison spectrum was also taken, exposure 

 being in this case 1 minute, the solution having previously been removed 

 from the source of light. 



The spectrogram shows the blue-violet band whose center is about 

 X 4250 and also the ultra-violet band. The blue-violet band gradually 

 disappears when the concentration is less than about 0.10 normal. The 

 uranyl bands come out quite strongly, but are not as intense as in the 

 methyl alcohol solution. The bands in ethyl alcohol occupy the same 

 positions as the uranyl bands do in a solution in methyl alcohol in which 

 there is 0.9 normal concentration of calcium chloride. In the 0.25 normal 

 solution the a band has divided into two faint bands whose centers are 

 about X 5000 and X 4900; the b band is at X 4750, c at A 4585, d and e at 

 X 4400, / at X 4250, g at X 4100, h at X 3985, and i at X 3865. 



The character of the a band is shown in A, Plate 57. This spectrogram 

 was taken under the same conditions as A, Plate 58, except that here the 

 depth of cell was 15 mm., whereas in the other spectrogram it was 6 mm. 



