50 THE ABSORPTION SPECTRA OF SOLUTIONS. 



for the purpose of making wave-length measurements. The first strip shows 

 the following bands: X 3200, X 3330, X 3500, X 3540, X 3640, X 3910, X 3925, 

 and some weaker bands farther towards the red. The third strip shows the 

 following bands: X 3200 quite weak; X 3330, X 3350, X 3430, and X 3450 very 

 weak and diffuse, appearing almost as a single band; X 3500, X 3540, X 3570, 

 X3640; X 3910, the strongest band in the spectrum, is about 35 Angstrom 

 units wide, X 3950 about 10 Angstrom units wide, X 3970 about 6 Angstrom 

 units wide, X 4060 and X 4100 are each about 30 Angstrom units wide and quite 

 weak. Other bands are easy to see and will be described in the last strip. In 

 this strip the ultra-violet absorption is complete to X 3350. In addition to 

 the bands mentioned above there were bands at XX 4290 weak, 4310 weak, 

 4350 weak, 4410 weak, 4520, 4545, 4570; this triple group is perfectly sym- 

 metrical, the middle band being much the strongest; 4650, 4705, and 4760 

 are each about 40 Angstrom units wide, are diffuse and weak with the middle 

 band having the greatest intensity; 4810 is about 10 Angstrom units in width, 

 4920 quite weak and diffuse, and 5200 is very weak. No other bands in the 

 longer wave-length region are visible in addition to those described. 



Samarium Chloride in Water and Ethyl Alcohol. 



The absorption spectra of samarium chloride in mixtures of water and 

 ethyl alcohol are given in B, plate 33, and B, plate 34. The change from the 

 alcohol to the water spectrum can easily be seen in the shift of the bands of 

 strip 1 compared with strip 2 in B, plate 34. The very great persistency of 

 the water bands is shown, since in this case (strip 2) only about 5 per cent 

 of water is present. The band X 3970 seems to be a characteristic water band. 

 In strip 1, B, plate 33, this band does not appear, but in strip 2 it can be 

 clearly seen and in the succeeding strips it becomes stronger. It seems, there- 

 fore, that the samarium bands behave in the same way as the neodymium 

 bands, although there is no single band that shows the effect as clearly as the 

 neodymium X 4271 water band, and the corresponding X 4290 alcohol band. 

 Since the water bands are so persistent it would be very interesting to carry 

 this work to temperatures almost as low as the freezing-point of alcohol. In 

 general, a lowering of temperature has increased the persistency of the water 

 bands. 



