COBALT CHLORIDE IN ETHYL ALCOHOL. 247 



The solution which contained 2 per cent of water transmitted a band of 

 red, like the mother-solution. Then the absorption was complete as far 

 as 0.629/(. Faint transmission began at 0.269/t and passed over into rather 

 strong transmission in the vicinity of 0.597,".. In other words, a single broad 

 band possessed by the mother-solution had broken up into two bands, of 

 which the more refrangible was much less intense and well defined than its 

 companion in the red. A relatively weak spot in the transmission appeared 

 near 0.52/<. 



The solution which contained 3 per cent of water had a complicated spec- 

 trum, very much like the spectra belonging to aqueous solutions of cobalt 

 chloride to which a comparatively large quantity of calcium chloride, of 

 calcium bromide, or of aluminium chloride had been added. The maximum 

 of transmission in the red was near 0.734/, and the adjoining region of intense 

 absorption had its maximum at about 0.690/. Then a series of bands of 

 incomplete opacity and transparency succeeded one another. The positions 

 of the maxima of absorption were recorded as 0.636,, 0.615/<, O.GOO/t, with 

 the brightest transmission at 0.627/t; 0.608/t marked the center of a very 

 faint maximum of transmission. The next region of relatively strong trans- 

 mission extended from 0.596/< to about 0.535/f. The band in the general 

 neighborhood of 0.52/t was weak and very diffuse at its limits. 



For the solution containing 4 per cent of water there were maxima of 

 transmission at 0.730/( and 0.627,".. The maxima of the absorption band had 

 the wave-lengths 0.695/!, 0.636/t, O.G15/<, and 0.600/<. The stronger band at 

 O.G95, transmitted a little light even at its maximum. The bunds at 0.615,u 

 and 0.600/t were very faint. The band in the green was too diffuse and indef- 

 inite to have the position even of its center or of its maximum determined. 

 For the 5.5 per cent solution the bands at O.GSG/i, 0.615.", 0.6()0/<, had 

 become so extremely faint that they could only be seen by moving the 

 spectrum across the field of view of the telescope. All the remaining bands 

 were much weaker. 



From the 7 per cent solution the band in the red had become very weak, 

 while for the 8 per cent solution it had become a mere shadow and lost its 

 identity as a band. 



A solution that contained 40 per cent of water exerted very slight absorp- 

 tion in the extreme red, and very weak diffuse absorption in the blue-green. 



COBALT CHLORIDE ix ACETONE. [See plate 26.] 



The concentration of the mother-solution of cobalt chloride in acetone 

 was 0.0154. The percentages of water in the solutions were 28, 2G, 24, 22, 

 20, 18, 10, 14, 12, 10, 8, 6, 4, 2, and 0. Each successive difference in 

 this sequence equals 2. When placed in the cell, at a depth of 2 cm., 

 the solutions whose percentages of water varied from 28 to 16, inclusive 

 of the latter number, were delicate pink. Beginning with the solution hav- 

 ing 14 per cent of water the color changed to blue, which was at first very 



