MISCELLANEOUS ABSORBING MEDIA. 



47 



150. Aluminium Chloride, etc. Continued. 

 lines in the remote ultra-violet, but 

 it absorbed the continuous back- 

 ground from o.20j, to about 0.288/11. 



The calcium bromide solution trans- 

 mitted nothino- between 0.20/K. and 

 2748.7. The intensity of this strong 

 cadmium line was greatly diminished. 

 The continuous background began to 

 be perceptible photographically at 

 about 0.313^. 



The calcium chloride solution trans- 

 mitted faintly all of the strongest 

 lines in the remote ultra-violet, but 

 it absorbed the continuous back- 

 ground from o.20ju, to about o.28o,u. 



Consequently there is no very marked 

 difference between the absorptions 

 exerted by the two chlorides. The 

 bromide, on the other hand, pos- 

 sesses much stronger absorption in 

 the ultra-violet region of the spec- 

 trum. 

 131. Barium Permanganate. 



The absorption is identical with that 

 of potassium permanganate solu- 

 tions, having the same concentration 

 in the MnO^ ions. See No. 179. 



152. Calcium Bromide. 

 See No. 150. 



153. Calcium Chloride. 

 See No. 150. 



154. Carborundum and Dia- <^^ a 



mond.* Q ^ 



Fig. 89, pi. 22. c=j c 



Eight crystalline plates of $ ^ 

 carborundum and three ^ * 

 of diamond were fastened f 

 to a strip of black paper 

 in such a manner as to 

 bridge across different 

 parts of a long, slit-like 

 opening in the paper. 

 The carborundum plates 

 varied in color from 

 visible transparency to 

 deep blue. The carbons 

 were colorless. The ac- 

 companying sketch shows 

 approximately the size, 

 shape, relative positions, 

 and distribution of blue of F'g- 7. 

 the plates, d, e, and / denote the 

 diamonds. The paper strip was slid 

 over the slit of the spectrograph, par- 

 allel to the length of this opening, 

 and successive exposures were taken. 



1 54. Carborundum and Diamond. Cont'd. 

 The absorption produced by plates 

 a, b, c, d, and e was first photo- 

 graphed, then the absorption of / 

 and ", next that of h and i, and 

 lastly, that of / and k. The spark 

 and glower exposures were 75 sec. 

 and 60 sec, respectively. 



Plate a was uniformly colored a blue 

 of moderate intensity. Its absorp- 

 tion is shown by the photographic 

 strip, the outer boundaries of which 

 are numbered i and 2. In cases 

 where the crystals were not in con- 

 tact the light passed through be- 

 tween them and produced narrow 

 comparison spectra ; for example, 

 the strip between Nos. 2 and 3. 



Plate b was almost colorless with a 

 frosted surface. Thickness 0.036 

 mm. Its absorption spectrum is the 

 strip between 3 and 4. 



Plate c had about the same color as 

 plate a. Thickness 0.173 "im- Its 

 absorption spectrum is the strip be- 

 tween 5 and 6. 



Plate d was a smooth, colorless car- 

 bon. Thickness 0.191 mm. Its 

 spectrum is between 6 and 7. c and 

 d were practically in contact. This 

 pair of plates shows how much more 

 transparent to ultra-violet light pure 

 carbon is than a colorless plate of 

 carborundum of comparable thick- 

 ness. Judging by the negative the 

 former transmits no light of wave- 

 length shorter than 2748.7 A. U., 

 whereas the latter absorbs everything 

 shorter than 0.390/14. 



Plate e had such an irregular surface 

 that the light transmitted by it did 

 not fall upon the sensitized film. 

 Thickness about 0.191 mm. The 

 blank between 10 and 11 is due to 

 translation of the photographic film 

 between the first and second settings. 



Plate / was a diamond with irregulari- 

 ties running parallel to the slit. 

 Thickness 0.533 mi''- Spectrum be- 

 tween II and 12. 



Plate g was a deeper blue than any of 

 the above-mentioned crystals in the 

 pentagon nearer plate /. The wide 

 border, extending around four sides 

 of the blue area, was practically 

 colorless. Thickness 0.602 mm. 



Kindly loaned by Mr. I,. E. Jewell, 



