DESCRIPTION OF PLATES. 105 



Plate 33. A. Samarium Nitrate in Water. Concentration, 1.06 normal. Depths of cell, 

 1, 4, 12, 22, and 22 mm. Strips 3 and 5 were exposed directly to the ultra- 

 violet spark lines. 

 B. Samarium Chloride in Ethyl Alcohol to which Water is gradually added. 

 The first strip represents the absorption of a 0.9 normal aqueous solution 

 of 5.5 mm. depth. To this solution were added small amounts of water, 

 so that the depths of cell were 5.5, 5.6, 5.7, 5.9, 6.0, 6.2, and 6.4 mm. 

 The change from the first to the second strip represents a change from 

 the alcohol to the water spectra. After the second strip there is very 

 little change in the spectrum. 



Plate 34. A. Samarium Chloride in Ethyl Alcohol. Concentration, 0.9 normal. Depths 

 of cell, 1, 4, 9, 18, 25, and 25 mm. The upper strip was exposed directly 

 to the ultra-violet spark lines. 

 B. Samarium Chloride in Ethyl Alcohol to which Water is added. The first 

 strip represents the absorption of a 0.09 normal solution in ethyl alcohol. 

 Succeeding strips represent the absorption of the same solution to which 

 small quantities of water have been added. Starting with the lowest strip 

 the depths of cell were: 18, 19, 20, 21.5, 22.5, 25, and 28 mm. 



Plate 35. A. Cobalt Bromide in Methyl Alcohol. Concentration, 0.2 normal. Depth 

 of cell, 1.0 cm. Current in the Nernst glower 0.8 amperes. Strip 1 was 

 exposed 4 minutes to the visible, and 4 minutes to the violet and ultra- 

 violet, the temperature being 29 C. Strip 2 was exposed 6 minutes to 

 the whole spectrum, at 44. Strip 3 was exposed 6 minutes at 57, and 

 strip 4, 15 minutes at 70. 

 B. This spectrogram shows the gradual oxidization of an aqueous solution of 

 Uranous Sulphate to which small amounts of Hydrogen Peroxide have 

 been added. The plate shows the gradual decrease in intensity of the 

 uranous bands, and the corresponding increase in intensity of the uranyl 

 bands. A spectrogram of this kind makes it very easy to differentiate 

 between the uranous and the uranyl bands. 



Plate 36. A. This plate represents the absorption of an acidified solution of Uranous 

 Chloride, dissolved in equal volumes of Water and Methyl Alcohol 

 (strip 1) to which was added a concentrated solution of Calcium Nitrate 

 dissolved in two parts of Water and three parts of Methyl Alcohol (suc- 

 ceeding strips). The original film shows very clearly the selective action 

 of the calcium nitrate on the water and alcohol bands, the water bands 

 becoming much weaker, whereas the alcohol bands remain of about con- 

 stant intensity. 

 B. Uranous Acetate in Water to which Nitric Acid is added. The first f out- 

 strips represent uranous acetate in water for different depths of cell, 

 the depth of cell in strip 4 being 2.0 cm. The succeeding strips show the 

 absorption of the same solution as that used in strip 4, increasing amounts 

 of nitric acid having been added. This spectrogram is then a spectro- 

 graph of the transformation of uranous acetate into uranous nitrate, and 

 then the oxidization of uranous nitrate to uranyl nitrate. 



Plate 37. A. Uranous Chloride in Water to which increasing amounts of Nitric Acid are 

 added. The first strip was accidentally exposed a short time dhectly to 

 the Nernst glower. This is a spectre-photograph of the chemical reaction 

 represented by uranous chloride being converted into uranous nitrate. 

 B. Uranous Chloride in equal parts of Water and Methyl Alcohol (strip 1) to 

 which Nitric Acid is added (strips 2, 3, and 4), and to which Hydrogen 

 Peroxide is added (strip 5). This spectrogram shows how the water 

 and alcohol bands of uranous chloride are changed to the nitrate 

 bands, and how these in turn are replaced by the uranyl nitrate bands. 

 The uranous nitrate bands are seen to be very different from the chlo- 

 ride bands. 



