AS AFFECTED BY TEMPERATURE. 11 



NEODYMIUM ACETATE IN WATER. (See Plates 5 and 6.) 



In plate 5 we have photographed the change in the absorption bands of 

 neodymium acetate, produced by rise in temperature, section A, and by the 

 corresponding lowering of temperature, section B. The concentration of 

 the solution used for both negatives was one-tenth of saturation; the depth 

 of absorbing layer was 10 cm. 



The temperatures of the strips in A, beginning with the strip nearest the 

 numbered scale, were 20, 45, 70, 95, 120, 140, 160, 190. This nega- 

 tive shows changes in bands X4275 and X5800; the former, as in the other 

 plates on the study of the effect of temperature, shows a marked shading 

 towards the red, while the remainder of this band virtually remains fixed. 

 The X5800 band widens rapidly toward the red, as the temperature is raised, 

 the total amount being about 80 a.u. All the absorption bands with the 

 acetate are more intense and broader than for the same concentration of any 

 of the other salts of neodymium studied. The acetate is not nearly so 

 soluble as the other salts, nor is the dissociation so great, yet we find in A, 

 which is the spectrogram of a one-tenth saturated solution of neodymium 

 acetate, greater changes than for the saturated solution of the chloride. 

 This is in accord with the results obtained from the effect of dilution; this, it 

 will be seen, was greatest with the acetate. This tends to strengthen the view 

 that the bands X4275 and X5800 are in some way associated with the molecules. 



In B of this plate there is given the spectrogram of the same solution as 

 the temperature was lowered. The temperatures, beginning with the strip 

 nearest the spark spectrum, were 190, 165, 145, 125, 100, 75, 50, 25; 

 the cell and arrangement of apparatus were the same as in A . The nega- 

 tive shows changes the reverse of those discussed in section A. The X4275 

 band gradually assumes the sharply defined edges as the temperature falls, 

 and strip 8 of B corresponds exactly to strip 1 of A . In a word, there has 

 been no permanent change produced by heating the solution. This change 

 in the width of the absorption bands could not have been produced by any 

 substance dissolved from any parts of the apparatus, as there is no reason to 

 suppose that this should disappear as the solution was cooled. It seems, 

 then, that the broadening is solely a temperature phenomenon. 



Plate 6 was made to show the relative effect of rise in temperature on a 

 solution of neodymium acetate, as compared with the same concentration 

 of neodymium chloride. The concentration in each case was one-tenth sat- 

 uration, the cell depth being 10 cm. The temperatures in A (neodymium 

 acetate), beginning with the strip nearest the numbered scale, were 20, 

 40, 60, 80, 100, and 125, respectively. The temperatures in B (neo- 

 dymium chloride), reading in the same order from the strip nearest the 

 spark lines, were 15, 40, 65, 90, 115, 140, 165, and 190, respectively. 

 A comparison of the two sections of this plate shows, first, that for the 

 same concentrations of the two salts the absorption bands are wider and 

 more pronounced with the acetate than with the chloride. 



In each of these plates only the X4275 and X5800 bands show appreciable 



