AS AFFECTED BY TEMPERATURE. 13 



PRASEODYMIUM CHLORIDE IN WATER. (See Plate 8.) 



A represents the effect of rise in temperature on the absorption spectra of 

 a 2.56 normal solution of praseodymium chloride, the depth of cell being 

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

 scale, were 20, 50, 80, 100, 120, 140, and 160, respectively. The orig- 

 inal film shows general transmission from A3400 to X4350, with the sharply 

 defined absorption band extending from X4300 to X4750. There is faint 

 transmission near X4550. There is practically no change in either edge of 

 this band as the temperature of the solution is raised. There is a slight 

 widening of that band whose center is near X4825. The X5900 band changes 

 less than 25 a.u. over the entire range of temperature studied. 



B is the absorption of a solution of the same salt, having a concentration 

 of 0.256 normal and a depth of layer of 10 cm. The temperatures, begin- 

 ning with the strip nearest the numbered scale, were 20, 40, 65, 90, 115, 

 140, 165, and 190, respectively. There are well-defined bands having 

 their centers near X4425, X4650, X4820, and X5900. None of these bands 

 shows any appreciable change with rise in temperature. 



PRASEODYMIUM NITRATE IN WATER. (See Plate 9.) 



The concentration of the solution used in making A was 2.6 normal; the 

 depth of cell, 1 cm. The temperatures, beginning with the strip nearest the 

 numbered scale, were 12, 32, 52, 72, 92, 112, 125, and 145, respectively. 



In the ultra-violet the absorption extends to about X3500 in strip 1, but 

 rapidly increases as the temperature is raised, until in strip 8 there is com- 

 plete absorption as far as X3800. 



There is a very intense double absorption band from X4350 to X4725 with 

 faint transmission near X4540. This transmission rapidly decreases as the 

 temperature is raised, and entirely disappears at a temperature slightly 

 above 100. The X4650 band widens towards the red end about 25 a.u. 

 Band X4825 shows a total widening of about 30 a.u. over the range of tem- 

 perature studied. The orange band near X5900 shows a uniform total wid- 

 ening of about 25 a.u. From this plate it is seen that none of the praseo- 

 dymium bands shows very marked change with rise in temperature; at this 

 concentration all of them become slightly wider at the higher temperatures. 



In section B of this plate is given the spectrogram of a 0.26 normal solu- 

 tion of the same salt, the depth of the absorbing layer being 10 cm. The 

 temperatures, beginning with the strip nearest the numbered scale, were 

 20, 45, 70, 95, 115, 135, and 165, respectively. On this plate, bands 

 appear which have their centers near X4425, X4650, X4825, and X5900; the 

 ultra-violet absorption bands near X3500. None of these bands shows any 

 appreciable change over the range from 20 to 165. 



The plate which was used to study the effect of dilution upon this same 

 salt reveals the fact that only in the most concentrated solutions were the 

 bands affected at all, while in the dilute solutions all the bands remained 

 unchanged. Plate 9 shows that temperature also has a slight effect only in 



