48 



ATLAS OF ABSORPTION SPECTRA. 



154. Carborundum and Diamond Cont'd. 



Spectrum between 13 and 14. / and 

 ij contrast diamond, colorless car- 

 borundum, and blue carborundum 

 with one another. The blank from 

 14 to 15 marks the second setting 

 of the film. 



Plate h had a delicate, uniform, blue 

 tint. Thickness 0.064 mm. Spec- 

 trum between 16 and 17. 



Plate i was a deeper blue than any of 

 the preceding crystals. Thickness 

 0.345 mm. Spectrum between 18 

 and 19. The blank from 19 t<.) 20 

 corresponds to the third setting of 

 the photographic film. 



The center of plate ;' was as deep in 

 color as the middle of / and it was 

 also the thickest plate studied. Thick- 

 ness 0.693 tfim- Spectrum between 

 20 and 21. 



Plate k was of a delicate blue color of 

 a slightly deeper hue than plates b 

 and c, except in the corner nearer ;. 

 In the latter place it had about the 

 same tint as plate /;. Thickness 

 0.097 it^n^. Spectrum between 22 

 and 23. 



155. Chromium Chloride. 



Fig- 79. Pl- 20. 



In solution very dark green, green. 



Saturated. 



Angle 50.7'. Depth, from nearly o to 

 0.46 mm. 



Strong absorption in the violet, blue, 

 orange, and red. 



Absorption was complete from o.20/t 

 to 0.303/1. The boundary of the 

 ultra-violet band curved around 

 from 0.303/1* to 0.328/it as the thick- 

 ness of absorbing layer increased 

 from its least to its greatest value. 

 Semi-transparency from 0.328/1 to 

 0.380/1. A wide, round band, with 

 its maximum near 0.438/1, absorbed 

 from 0.380/t to 0.498/1. This is fol- 

 lowed by fairly complete transmis- 

 sion from 0.498/i to O.SS5/1. The 

 orange and red region of absorp- 

 tion commenced at about 0.555/1. 



156. Cobalt Chloride. 

 Fig. 78, pl. 20. 



In solution red, rose-pink. 

 351-9 S- of anhydrous salt per liter 

 (2.71 normal). 



156. Cobalt Chloride Continued. 

 Angle 58.5'. Depth 0.53 to 1.07 mm. 

 One absorption band in the blue-green 



and another in the deep red.* Ab- 

 sorption was complete from 0.20/1 to 

 about 0.248/1. The solution was 

 quite transparent from 0.25/1 to 

 about 0.495/1. An absorption band, 

 with its maximum near 0.520/t, ex- 

 tended from 0.497/t to 0.542/1. Trans- 

 parent from the boundary of this 

 band as far as the deep red. 



1 57. Cobalt Chloride and Aluminium 



Chloride. 



Fig. 95, pl. 24. 



The plane-parallel cell was kept at the 

 constant depth of 1.41 cm. 



The successive solutions were made up 

 in the following manner : First, a 

 chosen volume of the mother-solu- 

 tion of cobalt chloride was run from 

 a burette or pipette into a measur- 

 ing flask. Next, a certain amount 

 of the mother-solution of aluminium 

 chloride was run into the same flask 

 and mixed with the solution of the 

 cobalt salt. Finally, distilled water 

 was added to the mixture until the 

 resulting solution filled up the meas- 

 uring flask to its calibration mark. 

 Of course, all the usual precautions 

 necessary to avoid errors due to 

 changes in volume on mixing and to 

 lack of homogeneity were taken. 

 Each solution of the series was made 

 up to the same volume and .~on- 

 tained the same amount of cobalt 

 chloride. On the other hand, the 

 mass of the dehydrating agent pres- 

 ent changed from one solution to 

 the next. 



The photographic strips nearest to the 

 numbered scale and to the compari- 

 son spectrum correspond, respec- 

 tively, to the solutions which con- 

 tained the least and greatest amounts 

 of the aluminium salt. The inter- 

 vening strips succeed one another in 

 the order of increasing percentages 

 of aluminium chloride. The con- 

 stant concentration of the cobalt 

 chloride in the solutions was 0.271 

 normal. The concentrations of the 

 aluminium chloride in the several 



For exhaustive details see "Hydrates in Aqueous Solution," etc. Harry C. Jones, Publication No. 60 of the 

 Carnegie Institution of Washington. 



