MISCELLANEOUS ABSORBING MEDIA. 



51 



161. Cobalt Glass Continued. 



glass wedge was approximately 9. 

 The compound system absorbed all 

 the ultra-violet from 0.20/i to 0.325/i. 

 The boundary of the ultra-violet 

 band does not curve or slant very 

 nuich with reference to the long axis 

 of the spectrogram because of the 

 absorption of the colorless glass in 

 this region of the spectrum. The 

 cobalt-glass transmits from about 

 0.327/x to o.497ja. Beginning at 

 0.497/1* a region of absorption ex- 

 tends into the red. The most re- 

 frangible band in this region has its 

 maximum near 0.52/j,. The mini- 

 mum of absorption between the band 

 just mentioned and the less refran- 

 gible, neighboring band is at wave- 

 length o.^Gofi. The band in the 

 orange extended into the red beyond 

 the field of view of the spectrograph. 

 These results were tested by using 

 a red-sensitive photographic plate. 



162. Cobalt Sulphate. 

 Similar to fig. 78, pi. 20. 



Reddish crystals. In solution red, sal- 

 mon pink. 



Saturated. 



Angle about 6. Depth o to about 3.2 

 mm. 



Rather weak absorption in the blue- 

 green. All of the strongest ultra- 

 violet lines were transmitted. The 

 continuous background was absorbed 

 from 0.20/H to about 0.255/n,. The 

 band in the blue-green extended 

 from 0.505/1 to 0.525/x with its center 

 near 0.5x5/1. 



163. Copper Chloride. 

 Fig. 77, pi. 20. 



Dark-green crystals. In solution dark 

 green, yellowish green. 



534.7 g. of anhydrous salt per liter 

 (3.98 normal). 



Angle 19.5'. Depth nearly o to 0.18 mm. 



Intense absorption in the red. The 

 solution was remarkable for its 

 strong absorption of the ultra-violet 

 radiations. Absorption was complete 

 from o.20/ii to 0.32/n at the thinnest 

 part of the wedge. The end of this 

 band curved around from 0.32/1 to 

 0.40/1. Transmission was complete 

 from about 0.40/1 to the orange. 



164. Copper Chloride and Calcium Chlo- 

 ride. 

 Fig. 92, pi. 23. 



The plane-parallel cell was kept at the 

 constant depth of 1.41 cm. The 

 several solutions were made up as 

 explained under No. 157, which see. 

 The photographic strips nearest to 

 the numbered scale and to the com- 

 parison spectrum correspond, re- 

 spectively, to the solutions which 

 contained the least and greatest 

 amounts of the calcium salt. The 

 intervening strips succeed one an- 

 other in the order of increasing per- 

 centages of calcium chloride. The 

 constant concentration of the cop- 

 per chloride in the solutions was 

 0.398 normal. The concentrations 

 of the calcium chloride in the sev- 

 eral solutions of the series were 

 0.000, 0.271, 0.541, 0.812, 1.082, 

 1.353, 1-624, 1-894, 2.165, 2.435, 

 2.706, 2.977, 3-247- 3-518, 3-788, and 

 4.041 normal. The addition of cal- 

 cium chloride to an aqueous solution 

 of copper chloride changes the color 

 of the latter from clear blue, through 

 green, to yellowish green, due to the 

 presence of an absorption band in 

 the red* and to the encroaching of 

 the ultra-violet band upon the violet 

 and blue. 



The solution which contained only 

 copper chloride absorbed all radia- 

 tions from 0.20/1 to about 0.361/1. 

 The solution which contained the 

 greatest amoiuit of the dehydrating 

 agent absorbed all radiations from 

 0.20/A to about 0.509/1. Hence, the 

 ultra-violet region of absorption 

 widened by about 1480 Angstrom 

 units when the concentration of the 

 calcium chloride was increased from 

 0.000 to 4.041 normal. The spec- 

 trogram shows clearly how the suc- 

 cessive increments of absorption de- 

 creased as the concentration of the 

 calcium salt increased in arith- 

 metical progression. Other dehy- 

 drating agents, such as aluminium 

 chloride, for example, produce sim- 

 ilar changes in the limits of ab- 

 sorption. 



For exhaustive details see " Hydrates in Aqueous Solution," 

 Carnegie Institution of Washington. 



etc. Harry C. Jones, Publication No. 60 of the 



