Chemical Constitution of Saline Solutions. 2907 
In order to be able to judge from absorption spectra of the condition of a 
salt when dissolved in water, and of any chemical change taking place when 
the solution is heated, it is necessary to know the answers to the following 
questions :— 
1st. How far do the absorption spectra of aqueous solutions of various salts of 
the same metal differ from one another, and how are salts affected by different 
solvents ? 
2nd. What change in the absorption of light is caused by heating coloured 
solutions to 100° C. ? 
3rd. Is there any remarkable difference between the spectra of hot and cold 
solutions which corresponds to the difference between the crystallized salts at the 
ordinary temperature and when dehydrated at 100° C. ? 
