DESCRIPTION OF THE PLATES. 



In the description of the plates there is usually given the time of exposure and 

 the quantity of current flowing through the Nernst glower. Almost invariably the 

 amount of light entering any solution is the same for every strip on any spectrogram. 

 For different spectrograms the amount of light varies according to the opacity of the 

 solution. In many cases where the solutions absorbed completely in the ultra-violet, 

 an exposure was made in the extreme ultra-violet only to the spark; the solution not 

 being in the path of the beam of light. These spark lines were used as wave-length 

 references. In making an exposure to a reference line the film holder was never moved, 

 so that there was no possibility of shifts. In a few cases there are streaks running 

 parallel to the strips. This is due to bubbles or some other obstacles in the solution 

 opaque to the light. Glycerol solutions present many difficulties of this kind. One 

 of these is the inequalities in a glycerol solution produced by heating. One way of mak- 

 ing the light illumination across any strip more uniform, is by moving the solution back 

 and forth in the path of the beam of light. 



Plate 1. A. Potassium Chromate. Depth of cell constant, 3 mm. Concentrations, 

 2, 1.5, 1, 0.66, 0.46, 0.33 and 0.25 normal. 

 B. Potassium Chromate. Depth of cell constant, 3 mm. Concentrations, 0.25, 

 0.19, 0.12, 0.08, 0.06, 0.04, and 0.031 normal. 

 Plate 2. A. Potassium Chromate. Depth of cell constant, 3 mm. Concentrations, 

 0.031, 0.023, 0.0156, 0.0103, 0.0072, 0.0052, and 0.004 normal. 

 B. Potassium Chromate. Depth of cell constant, 3 mm. Concentrations, 

 0.004, 0.003, 0.002, 0.0013, 0.0009, 0.00065, and 0.0005 normal. 

 Plate 3. A. Potassium Chromate, Beer's Law. Depth of cell, 3, 4, 6, 9, 13, 18, 

 and 24 mm. Concentrations, 2. 1.5, 1, 0.66, 0.46, 0.33, and 0.25 

 normal. 

 B. Potassium Chromate, Beer's Law. Depth of cell, 3, 4, 6, 9, 13, 18, and 

 24 mm. Concentrations, 0.25, 0.19, 0.12, 0.08, 0.06, 0.04, and 0.031 

 normal. 

 Plate 4. A. Potassium Chromate, Beer's Law. Depth of cell, 3, 4, 6, 9, 13, 18, and 

 24 mm. Concentrations, 0.031, 0.023, 0.0156, 0.0103, 0.0072, 0.0052, 

 and 0.004 normal. 

 B. Potassium Chromate, Beer's Law. Depth of cell, 3, 4, 6, 9, 13, 18, and 

 24 mm. Concentrations, 0.004, 0.003, 0.002, 0.0013, 0.0009, 0.00065, 

 and 0.0005 normal. 

 Plate 5. A. Potassium Dichromate, Beer's Law. Depth of cell, 3, 4, 6, 9, 13, 18, and 

 24 mm. Concentrations, 0.33, 0.25, 0.16, 0.11, 0.077, 0.055, and 0.042 

 normal. 

 B. Potassium Dichromate. Depth of cell constant, 3 mm. Concentrations, 

 0.33, 0.25, 0.16, 0.11, 0.077, 0.055, and 0.042 normal. 

 Plate 6. A. Potassium Dichromate. Depth of cell constant, 3 mm. Concentrations, 

 0.042, 0.031, 0.02, 0.014, 0.0096, 0.007, and 0.0052 normal. 

 B. Potassium Dichromate. Depth of cell constant, 3 mm. Concentrations, 

 0.005, 0.004, 0.0025, 0.0017, 0.0012, 0.009, and 0.0006 normal. 

 Plate 7. A. Potassium Dichromate, Beer's Law. Depth of cell, 3, 4, 6, 9, 13, 18, and 

 24 mm. Concentrations, 0.041, 0.031, 0.02, 0.014, 0.0096, 0.007, and 

 0.0052 normal. 

 B. Potassium Dichromate, Beer's Law. Depth of cell, 3, 4, 6, 9, 13, 18, and 

 24 mm. Concentrations, 0.005, 0.004, 0.0025, 0.0017, 0.0012, 0.009, 

 and 0.0006 normal. 



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