AS AFFECTED BY TEMPERATURE. 9 



and section B made with falling temperature. In B the temperatures were 

 165, 140, 115, 95, and 70, the highest temperature being nearest the 

 numbered scale, which is not accurately adjusted. 



A study of the original film shows changes only in bands X4275 and X5800; 

 and this change is exactly the reverse of that shown by these same bands in A. 

 The X4275 band appears in strip 1, with a sharp violet edge and shading off 

 toward the red over a range of 15 or 20 a.u. As we pass to the succeeding 

 strips in the direction of falling temperature the red edge becomes sharper 

 and sharper, until in strip 5, which represents the lowest temperature, the 

 band assumes its normal sharp edge on the red side and covers less than 10 

 a.u. The X5800 band narrows uniformly from the red end as the tem- 

 perature falls, the total narrowing being about 40 a.u. 



NEODYMIUM BROMIDE IN WATER. (See Plate 2.) 



The concentration of the solution used in making the negative for A was 

 1.66 normal; the depth of cell, 1 cm. The temperatures, beginning with the 

 strip nearest the numbered scale, were 20, 45, 70, 95, 120, 140, 175, and 

 190, respectively. This plate seems to have had just the proper length of 

 exposure for the given concentration, and every known neodymium absorp- 

 tion band appears on the negative in excellent condition. With the bromide, 

 as with the chloride discussed in plate 1, only X4275 and X5800 show appre- 

 ciable changes with rise in temperature. The X4275 band, which has both 

 violet and red edges sharp in strip 1, feathers out toward the red end of the 

 spectrum as the temperature is raised. 



The X5800 band widens toward the red as much as 60 a.u. The concen- 

 tration of solution used in making B was 0.166 normal, one-tenth that of A; 

 the depth of absorbing layer was 10 cm. The temperatures, beginning with 

 the strip nearest the numbered scale, were 20, 45, 70, 95, 115, 135, 

 1 55 and 190, respectively. This is probably the best negative produced in 

 this part of the work, and the bands X4275 and X5800 show well the char- 

 acteristic changes spoken of above. The widening of band X5800, though 

 well marked, is not so great as in A, the total change being about 40 a.u., 

 as compared with 60 a.u. in the former. If such a band be due to mole- 

 cules this is what we should expect, since, B being a more dilute solution, the 

 total number of molecules is less than in A. Hence, any change associated 

 with molecules would be more clearly apparent in A. This is in accord with 

 changes produced in this same band by dilution. 



NEODYMIUM NITRATE IN WATER. (See Plates 3 and 4.) 



The solution used in spectrogram A, plate 3, was saturated, the depth of 

 cell being 1 cm. The temperatures, beginning with the strip nearest to the 

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



The exposures were not as long here as in the previous plates, in order to 

 bring out more clearly the group of bands between X4200 and X4800. The 

 change in the X4275 band is here especially marked. At 15 this band i<5 

 very sharp and intense, while at 165 it has become broad and hazy, being 



