16 ABSORPTION SPECTRA OF SOLUTIONS. 



of transmission near X 2900 is very well shown in B. The absorption in 

 the extreme ultra-violet seems to remain sensibly constant in B, the limit 

 of transmission being X 2700 throughout. 



The band in the green is peculiar. In A its violet edge moves farther 

 clown into the violet, and in such a w r ay that the limits of transmission 

 for the seven strips lie almost exactly on a straight line, the total dis- 

 placement being 100 Angstrom units or from X 4550 to X 4450. The red 

 edge of the band at first moves towards the violet, then turns and moves 

 towards the red as the dilution increases. On the whole the absorption 

 band widens with dilution, but from concentration 2.5 to 1.14 its center 

 moves towards the violet by about 50 A. U., after which it remains prac- 

 tically unchanged in position. In B the band widens with dilution and 

 very nearly uniformly, the apparent asymmetry being due to the greater 

 sensitiveness of the Seed film to yellow light. 



COBALT CHLORIDE IN METHYL ALCOHOL BEER'S LAW. (See Plate 4.) 



The concentrations of the solutions used in making the negative for 

 A were 0.25, 0.21, 0.174, 0.143, 0.118, 0.100, and 0.083; the correspond- 

 ing depths of cell were 8, 9.5, 11.5, 14, 17, 20, and 24 mm., respectively. 

 For B the concentrations were 0.143, 0.120, 0.100, 0.082, 0.0675, 0.057*2, 

 and 0.0476; the depths of cell were the same as for set A. The most con- 

 centrated solutions had a very deep purple color which, as dilution in- 

 creased, changed to pink. The solutions for set A exerted considerable 

 general absorption, so that in order to get a satisfactory spectrogram the 

 slit was opened to 0.015 cm. and the exposures to the Nernst lamp and 

 spark were, respectively, 3 and 4J minutes. In making the negative for 

 set B the slit was set at 0.01 cm. and the exposures were 1J and 3 minutes, 

 respectively, for the Nernst lamp and spark. 



Both A and B show a region of absorption in the extreme ultra-violet 

 which narrows slightly with dilution. In A the limits of transmission for the 

 most concentrated and most dilute solutions are X 2630 and X 2600, respec- 

 tively, while in B the limit is at X 2570 throughout. The strips corresponding 

 to the more concentrated solutions (those nearest the numbered scale) in A 

 show the presence of two faint absorption bands, having centers at X 3100 

 and X 3600, respectively. Both of these disappear gradually with dilution. 



The absorption band in the green has its center at X 5250 in both A 

 and B. It narrows somewhat with dilution in A, whereas in B it remains 

 of sensibly constant width. 



In the orange and red is a rather complicated group of absorption 

 bands, the absorption of the most concentrated solution of set A beginning 

 at about X 5850 and extending to a little beyond X 7000. With dilution 

 this absorption decreases rapidly, breaking up into bands, the position 

 and character of which are as follows: 



1. Fairly narrow band, with center at X 5910; appearing on the nega- 

 tive as far as the sixth strip in A. 



2. Band with center at X 6050, which is visible in the strip corresponding 

 to the fifth solution of A. This band and the one at X 5910 are not clearly 

 separated in the strips corresponding to the first and second solutions. 



