CHEMISTRY — JONES. 21 5 



were studied. The absorption spectra of the different concentrations of co- 

 balt chloride, cobalt nitrate, cobalt acetate, cobalt sulphocyanate, cobalt sul- 

 phate, nickel sulphate, nickel acetate, nickel chloride, chromium nitrate, chro- 

 mium chloride, chromium sulphate, chromium acetate, potassium chromium 

 sulphate, copper nitrate, copper bromide, uranyl sulphate, uranyl nitrate, 

 uranyl chloride, uranyl acetate, uranous chloride, the chloride, bromide and 

 nitrate of neodymium, the chloride and nitrate of praeseodymium, and 

 erbium chloride have been investigated between 0° and 90°. Various mix- 

 tures of the above chlorides with calcium and aluminium chlorides have also 

 been studied. 



For every solution investigated of a single salt in a single solvent, it was 

 found that the change in the absorption spectra with rise in temperature was 

 much greater for the more concentrated solutions, and as the solutions be- 

 came more and more dilute the effect of rise in temperature became gradually 

 less and less. 



The temperature effect, however, in the case of a dilute solution of one salt 

 in a concentrated solution of another salt may be very great. An example 

 of this is a dilute solution of cobalt chloride in a concentrated solution of 

 aluminium chloride. To summarize briefly, the effect of rise in temperature 

 on absorption spectra : 



(i) Of the colored solutions thus far investigated practically all show in- 

 creased absorption with rise in temperature. 



(2) Many broad bands such as those of cobalt, chromium, and a few of 

 the wide bands of concentrated solutions of the neodymium salts widen 

 unsymmetrically, and this widening is invariably the greatest on the long 

 wave-length edge of the bands. 



(3) Some of the finer bands are shifted to the red with rise in tempera- 

 ture, without much or any widening of the bands. Good examples of this 

 kind of shift are aqueous solutions of uranyl chloride and uranyl sulphate. 



(4) The addition of calcium chloride or aluminium chloride to chromium 

 chloride causes the chromium bands to widen entirely on their red edges, and 

 may even cause the bands to narrow on their short wave-length edges. 



(5) For aqueous solutions of salts of neodymium and erbium no shift of 

 the bands was noticed with rise in temperature. The addition of calcium 

 chloride to the solution of neodymium chloride caused the neodymium bands 

 to shift to the red with rise in temperature, and also produced a weakening 

 of some of the bands. The presence of aluminium chloride and calcium chlo- 

 ride seems to play a very important role in the effect of temperature on the 

 absorbing power of solutions. 



