DESCRIPTION OF PLATES. 



Plate 



1. A. Neodymium Chloride in Aqueous Solution. Concentration, saturated. Depth 



of layer, 1 cm. Respective temperatures, 20, 45, 70, 95, 115, 140, and 

 165, with lowest temperatures nearest spark lines. Exposures made on 

 rising temperature. 

 B. The same solution used in A, with exposures made as cell cooled. Depth of layer 

 and concentration the same as in A. Temperatures, 165, 140, 115, 95, 

 70, respectively. Highest temperatures nearest spark lines. 



2. A. Neodymium Bromide in Aqueous Solution. Concentration, 1.66 normal. Depth 



of cell, 1 cm. Respective temperatures, 20, 45, 70, 95, 120, 140, 175, 

 190. Lowest temperature nearest spark spectra. 

 B. Neodymium Bromide in Aqueous Solution. Concentration, 0.166 normal. 

 Depth of cell, 10 cm. Respective temperatures, 20, 45, 70, 95, 115, 

 135, 155, and 190. Highest temperature nearest spark spectra. 



3. A. Neodymium Nitrate in Water. Concentration saturated; depth of cell, 1 cm. 



The temperatures, beginning with the strip nearest the numbered scale, 

 were 15, 40, 65, 115, 140, and 165, respectively. 

 B. Neodymium Nitrate in Water. Concentration, one-tenth saturation, depth of 

 cell, 10 cm.; temperatures, 20, 45, 70, 95, 120, and 145, respectively. 

 Lowest temperature nearest the numbered scale. 



4. A. Neodymium Nitrate in Aqueous Solution. Concentration, 0.1 saturated. Depth 



of layer, 10 cm. Temperatures, 20, 45. 70, 95, 115, 140, 165, 190. 

 Exposures made as temperature was raised. Lowest temperature nearest 

 spark lines. 

 B. The same solution of neodymium nitrate as used in A . Concentration and depth 

 of layer identical with A. Temperatures, 190, 165, 140, 115, 95, 70, 

 45, and 20. Exposures made on falling temperatures. Highest tempera- 

 tures nearest spark lines. 



5. A. Neodymium Acetate in Water. Concentration, 0.1 saturated. Depth of cell, 



10 cm. Trace of acetic acid added to prevent precipitation. Tempera- 

 tures, 20, 45, 70, 95, 120, 140, 160, and 190. Exposures made on 

 rising temperature. Lowest temperature nearest spark line. 

 B. Solution, depth of cell and concentration the same as A. Temperatures, 190, 

 165, 145, 125, 100, 75, 50, and 25. Exposures made on falling 

 temperatures. 



6. A. Neodymium Acetate in Water. Concentration, one-tenth saturation; depth of 



absorbing layer, 10 cm. The temperatures, beginning with strip nearest 

 the numbered scale, were 20, 40, 60, 80, 100, and 125, respectively. 

 B. Neodymium Chloride in Water. Concentration one-tenth saturation; depth of 

 cell, 10 cm. The temperatures, beginning with the strip nearest the 

 numbered scale, were 15, 40, 65, 90, 115, 140, 165, and 190, respec- 

 tively. 



7. A. Neodymium Sulphate in Water. Concentration was saturation, cell depth, 10 cm. 



Temperatures, beginning with the strip nearest the numbered scale, were 



20, 45, 75, 90, 115, and 140. 

 B. Cobalt Chloride in Water. Concentration, 0.25 normal; depth of cell 1 cm. 



Temperatures, 12, 32, 52, 76, 92, 112, 132, and 152, respectively. 



The lowest temperature was nearest the numbered scale. 

 S. A. Praseodymium Chloride in Water. Concentration, 2.56 normal; depth of 



absorbing layer 1 cm. Temperatures, beginning with strip nearest the 



numbered scale, were 20, 50, 80, 100, 120, 140, and 160, respectively. 

 B. Praseodymium chloride in water. Concentration, 0.256 normal; depth of cell, 



10 cm. Beginning with the strip nearest numbered scale, the temperatures 



were 20, 40, 65, 90, 115, 140, 165, and 190, respectively. 

 9. A. Praseodymium Nitrate in Water. Concentration, 2.6 normal. Cell depth, 1 cm. 



Temperatures, 12, 32, 52, 72, 92, 112, 125, and 145. Lowest 



temperature nearest spark lines. 

 B. Praseodymium Nitrate in Water. Concentration, 0.26 normal. Cell depth, 



10 cm. Temperatures, 20, 45, 70, 95, 115, 135, and 165. Lowest 



temperature nearest spark lines, 

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