On the Chemical Action of Water on Soluble Salts. 67 



This was closely examined. It might be expected, a, prioii, that 

 a certain amount of salt would have the same absorbent effect on a 

 given quantity of light, whether it were dissolved in much or little 

 water, and that as the absorbent power of water is practically nil, it 

 would appear to the eye of precisely the same depth and character 

 of colour in the two cases. And this actually holds good in the 

 majority of instances ; but to prove it a special contrivance was 

 necessary, in order to make the same quantity of light impinge upon 

 the solution before and after dilution. This was effected by means 

 of colourless cylindrical glasses of uniform diameter and the same 

 size, closed at one end with a flat plate of glass, so that when placed 

 upright they could hold liquids : they stood in a case so contrived 

 that all the light which passed through the strong or diluted solu- 

 tion, as looked through from above, had to enter by the flat plate 

 at the bottom. Every experiment was performed by a comparative 

 method, two glasses being placed side by side, one containing the 

 solution to be diluted, the other a similar quantity of the same solu- 

 tion which served as a standard. 



In this manner it was determined that the following salts absorbed 

 the same light whether dissolved in much or in little water : — 



Ferrous Sulphate. 

 Ferric Nitrate. 

 Ferric Meconate. 

 Ferric Comeuate. 

 Ferric Comenaraate. 

 Ferric Gallate. 

 Nitrate of Nickel. 

 Nitrate of Cobalt. 

 Sulphate of Cobalt. 

 Chloride of Chromium. 

 Acetate of Chromium. 

 Chromate of Chromium. 

 Nitrate of Uranium. 

 Chloride of Uranium. 



Terchloride of Gold. 

 Terbromide of Gold. 

 Protochloride of Platinum 



(in hydrochloric acid). 

 Bichloride of Platinum. 

 Bichloride of Palladium. 

 Chromate of Potash. 

 Ferrocyanide of Potassium. 

 Ferridcyanide of Potassium. 

 Nitroprusside of Sodium. 

 Sulphindigotic Acid. 

 Sulphindigotate of Ammonia. 

 Carbazotate of Copper. 

 Pentasulphide of Potassium. 



Sulphate of Ceric Oxide. 

 The following salts were affected in regard to their absorption of 

 light, by adding water to their saturated solutions : — • 



F2 



