CHAPTER I. 



INTRODUCTION. 



An investigation of the effect of temperature on the absorption spectra 

 of certain solutions has already been carried out by Jones and Strong. 1 

 The apparatus used was devised by Professor John A. Anderson, 2 who 

 worked somewhat earlier with Jones on the absorption spectra of solutions. 

 The solutions were heated in an open vessel, and the temperature could, 

 of course, not be raised much above 100 F. It was found that, even over 

 this range of temperature, the effect of rising temperature was to cause the 

 general absorption of any salt in water to increase, and also to cause the 

 bands to broaden and become more diffuse. The results were entirely 

 unambiguous so far as they went, but were limited by the boiling-points of 

 the solutions in question. Indeed, it was not possible to work quite up to 

 the boiling-point of the solution, since the change in the concentration of 

 the solution resulting from boiling would have been too great, and there 

 would have been too much gas formed on the quartz windows through which 

 the light was to pass. 



We wanted to study the effect of rise in temperature on the absorption 

 spectra of solutions to as high temperatures as it was possible to go. For 

 this purpose closed forms of apparatus devised by Anderson 3 and by Strong 4 

 were employed by Jones and Strong 5 for nonaqueous solutions. The appa- 

 ratus consisted of a gold-plated steel tube, whose ends were closed with 

 glass windows. This worked very well with nonaqueous solvents up to 

 temperatures of approximately 200 C. Usually before this temperature 

 was reached a precipitate formed in the tube, which prevented work at 

 higher temperatures. 



Some interesting results were obtained at the higher temperatures with 

 this apparatus. The general effect of rise in temperature is to deepen the 

 color of the solution of an inorganic salt. This is usually due to a widening 

 of the absorption bands. For details in reference to the effect of tempera- 

 ture on the absorption of light by nonaqueous solutions, reference must be 

 had to the Carnegie Institution of Washington monograph, 6 where the 

 results in question are published in full. 



The apparatus used by Jones and Strong for nonaqueous solutions did 

 not work satisfactorily for solutions in water as the solvent. The water 

 vapor, under the high pressure produced within the apparatus, worked its 



^arn. Inst. Wash. Pub. 130. Amer. Chem. Journ., 43, 37, 97 (1910); 45, 1, 113 (1911). 



2 Carn. Inst. Wash. Pub. 110, p. 20. Amer. Chem. Journ., 41, 276 (1909). 



3 Carn. Inst. Wash. Pub. 160, p. 28. Amer. Chem. Journ., 47, 30 (1912). 



4 Carn. Inst. Wash. Pub. 160, p. 29. Amer. Chem. Journ., 47, 30 (1912). 



6 Carn. Inst. Wash. Pub. 160. Amer. Chem. Journ., 47, 27, 126 (1912). 



6 Cam. Inst. Wash. Pub. 160. 



1 



