MISCELLANEOUS ABSORBING MEDIA. 



55 



176. Nickel Sulphate Continued. 



with its maximum at 0.391/x, ex- 

 tended from 0.367/14 to 0.415/*. 

 Transmission was complete from 

 this point as far as the absorption 

 band in the orange. A comparison 

 of figs. 81 and 82 is very sugges- 

 tive. Both spectrograms show the 

 same band at wave-length 0.391/*, 

 but the ultra-violet absorption ex- 

 erted by the nitrate is entirely dif- 

 ferent from that shown by the sul- 

 phate. 



177. Picric Acid. 'Hj^ 

 Fig. 86, pi. 22. 



Yellow crystals with greenish hue. 

 In solution yellow, pale yellow. 



Concentration unknown. 



Angle 50.7'. Depth o to 0.46 mm. 



Hazy band in the violet extending 

 into the ultra-violet. Absorption 

 decreased gradually from 0.20/1 to 

 partial transparency at 0.275/1. 

 Semi-transparency from 0.275/1 to 

 0.300/i. A band of absorption, with 

 hazy contour, extended from about 

 0.300/1 to 0.400/t, its maximum being 

 near 0.35/1. 



178. Potassium Chromate. 

 Fig. 80, pi. 20. 



Yellow crystals. In solution yel- 

 low, faint yellow. 



Very dilute. 



Angle 50.7'. Change in depth 0.46 

 mm. 



Absorption in the extreme violet ex- 

 tending into the ultra-violet. The 

 most refrangible absorption band 

 only extends from beyond 0.20/1 to 

 0.226/1. The solution is noticeably 

 transparent to all radiations from 

 2265.1 A. U. to 2321.2 A. U., inclu- 

 sive of these limits. An intense 

 band extends from 0.227/1 to 0.300/1. 

 This is followed by a region of al- 

 most complete transparency, the 

 middle of which is near 0.316/1. A 

 strong band of absorption extends 

 from 0.332/1 to 0.406/1 with its max- 

 imum at 0.369/1. 



179. Potassium Permanganate. 

 Figs. 74 and 75, pi. 19. 

 Grayish-brown crystals with violet 



reflex. In solution deep violet, 

 violet. 



179. Potassium Permanganate Continued. 



16.67 S- P^^ liter. 



Angle 27.3'. Depth o to 0.25 mm. 



Five distinct bands clearly visible 

 in the green with a very faint com- 

 panion on the blue side. The cen- 

 tral band of the five is a little 

 more intense than its less re- 

 frangible neighbor. Light from the 

 spark decomposes the potassium 

 permanganate so rapidly, with the 

 formation of innumerable small 

 bubbles, that the exposures had 

 to be made as follows : 1st. Expose 

 to spark for 25 seconds. 2d. Re- 

 move cell from spectrograph and 

 clean away the bubbles. 3d. Re- 

 place the cell and make another 

 exposure for 25 seconds, etc., three 

 times for each distinct strip of the 

 spectrogram. The absorption at 

 0.20/1 is weak and decreases to 

 transparency near 0.25/1. Unusual 

 transparency from 0.25/1 to 0.29/1. 

 This fact is brought out in a half- 

 dozen spectrograms of the region. 

 A band of absorption extends 

 roughly from 0.29/1 to 0.36/1 with 

 its maximum at the center. The 

 transparency increases to com- 

 pleteness and continues to 0.483/1. 

 The wave-lengths of the 7 photo- 

 graphic bands are 0.457/1, 0.472/1, 

 0.488/*, 0.505/1, 0.525/1, 0.545/1, 

 and 0.570/1. (Only 5 bands show on 

 the complete spectrogram.) In 

 decreasing order of intensity the 

 three strongest bands are 0.525/1, 

 0.505/* and 0.545/*. 



An effort was made to detect the 8 

 bands given by Formanek,* but 

 the conditions were not favorable 

 to recording more than seven 

 bands. Formanek's wave-lengths 

 are "571.0, 547.3 (Hauptstreifen), 

 525.6, 505.4. 487.0, 470.7, 454.4, 

 and 439-5-" 



The negative for fig. 75, pi. 19, shows 

 the seven bands. The solution 

 was practically saturated since it 

 contained 50 grams per liter at 

 room temperature. Here the ultra- 

 violet absorption extends as far as 

 0.39/1. For concentrations from 

 16.67 to 50 grams per liter, and for 



*SeeJ. FormSnek, "Die qualitative Spectralanalyse auorganischer Korper," p. 59. 



