GENERAL SUMMARY OF RESULTS. 93 



near X4600 and another near X5900. We have limited our investigations to 

 the latter band, on account of the small amount of energy transmitted at 

 X4600. The curves representing the absorption of different concentrations 

 of praseodymium chloride are identical to within the limits of possible experi- 

 mental error. The results obtained with the radiomicrometer arc in accord 

 with those found by the grating and photographic plate. The minimum in 

 each case occurs near X5900. The total deviation from Beer's law, as shown 

 by solutions of praseodymium chloride, is within the limits of experimental 

 error. 



The curves for praseodymium nitrate show that Beer's law holds here as 

 well as for the chloride. 



Solutions of nickel chloride show an increasing absorption from X5200 

 to X6300, where it is complete. Complete absorption extends to X7200. 

 Transmission increases to X9000, then decreases to zero at X10000. The 

 visible spectrum of salts of nickel consists of intense broad absorption bands 

 in the blue and red, having a single region of transmission in the red, extend- 

 ing to about X6500. By means of the radiomicrometer we could study the 

 region of transmission near X9000. Beyond this we could not go because of 

 the absorption of the water. 



The absorption of nickel nitrate closely resembles that of the chloride. 

 There is maximal absorption at X5400 and X9000. There is complete absorp- 

 tion in the region X7000 and beyond 1.1/z. 



The solution of nickel sulphate studied is slightly more dilute than the 

 chloride and nitrate. In no region is there complete absorption. There is 

 maximal transmission near X5400 and X9000, and minima at X6900 and 

 XI 1000. Readings were not extended beyond this region on account of the 

 intense absorption of the water. The three salts of nickel studied have just 

 about the same absorption spectra, the curves showing maxima and minima 

 in just about the same regions of the spectrum. 



Salts of cobalt in the visible region have a strong ultra-violet absorption 

 There is a band in the orange near X5000, and increasing transmission 

 towards the red. The infra-red absorption of solutions of cobalt salts was 

 studied, and the absorption of the chloride, bromide, nitrate, sulphate, and 

 acetate compared. The transmission curves for all of these salts have 

 maxima at X5950, X7800, X9100, and X10600. 



The transmission curves for all of the salts of cobalt studied rise rapidly 

 from X5000 to X5900. The curves show a broad, slight absorption over the 

 region near X6500, and reach a maximum transmission from X7000 to X8000. 

 There is a series of small absorption regions near X8400, X8900, and X9800. 

 Beyond X10500 the absorption increases rapidly to the region where water 

 is practically opaque. 



The curves for cobalt sulphate are slightly better defined than those for 

 the other cobalt salts. 



