CHAPTER II. 



ABSORPTION SPECTRA OF AQUEOUS SOLUTIONS AS AFFECTED 



BY TEMPERATURE. 



Jones and Strong 1 studied the effect of temperature on the absorption 

 spectra of various nonaqueous solutions up to nearly 200. The solutions 

 were usually heated until a precipitate formed, which cut off the light and 

 prevented work at still higher temperatures. Some work was also done by 

 Jones and Strong on the effect of temperature on the absorption spectra of 

 aqueous solutions. This was, however, not large in amount and did not 

 extend to very high temperatures. 



The reason that the work with aqueous solutions was not pushed to higher 

 temperatures was that the form of apparatus then in use did not admit 

 of it. This consisted of a steel tube, 2 lined on the inside with copper and 

 plated with gold on all of the inner surfaces. This worked very satisfac- 

 torily with nonaqueous solutions, the gold plate adhering firmly to the 

 copper, which, in turn, remained adherent to the steel. When an aqueous 

 solution was heated in the apparatus from 100 to 200 the result was 

 unsatisfactory. The water, under the high pressure, forced its way through 

 the copper and the gold and rusted the iron, as has already been stated. 

 The result was that the copper, with the gold, separated from the steel, and 

 the solutions, after heating for a time, gave the iron reaction. This appa- 

 ratus had the further disadvantage, that when a precipitate formed with 

 rising temperature it was necessary to open the entire apparatus and remove 

 the glass ends in order to clean them. 



To overcome these difficulties the apparatus shown in fig. A was con- 

 structed by Jones and Strong and used to study the effect of rising tempera- 

 ture on the absorption spectra of aqueous solutions. The quartz ends are 

 fastened into the ends E' . The plunger P has guide grooves instead of 

 guide pins. A part of the plunger is provided with screw-threads for remov- 

 ing it. The entire cap is removed from tube T by unscrewing E', during 

 which the quartz end is untouched. When the ends are removed the quartz 

 window can be easily cleaned. Gold washers were inserted between T and 

 E' and between E' and U. 



The general arrangement of the apparatus is also shown in fig. A. The 

 cell is kept in a horizontal position, so that any bubbles that may form will 

 rise in the side tube. The spectroscope, containing the grating G, photo- 

 graphic-plate holder C, and slit S, being kept vertically, a 45 quartz prism 

 was used to change the horizontal beam of light into a vertical beam, the 

 beam being totally reflected by the hypothenuse surface of O. The source 

 of light NG (Nernst glower) or SG (spark gap) was focused by the concave 



^mer. Chem. Journ., 47, 27, 126 (1912). Hbid., 47, 30 (1912). 



5 



