28 



STUDY OF ABSORPTION SPECTRA 



parent than the solvent. No such differences were found at or near the 

 1.25/.t water-band for any of the other hydrated salts that were studied. 

 The solution of the calcium chloride used was nearly 5 times normal, and 

 it was found that the above-named differences increase with increase in 

 concentration. This was expected, since the total amount of combined 

 water increases with the concentration of the solution. 



The first column of table 12 contains the percentage transmissions 

 for 20 mm. of water, while that of table 13 gives the transmissions for 

 10 mm. of water. The figures given are the averages of several series 



TABLE 11. Depth of cell 10 mm. Transmission of zinc nitrate, calcium 



chloride, and water. 



of measurements. Three of these series are given in tables 10 and 11 

 These transmissions of the solvent are to be compared with the two 

 series of results for magnesium nitrate and sodium nitrate, and with 

 that for ammonium bromide. A sufficient depth of solution was used 

 to contain 21 mm. of water in one cell and 1 mm. of water in the second 

 cell, these being the depths of layers employed in determining the 

 percentage transmissions for 20 mm. of the solvent. In obtaining the 

 results recorded in table 13, one cell had enough solution to contain 

 11 mm. of water, while the second had enough solution to contain 



