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 Comenate. 

 Ferric Comenamate. 

 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. 

 Sulphate of Ceric Oxide. 



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. 



The following salts were affected in regard to their absorption of 

 light, by adding water to their saturated solutions : 



That these changes of colour are due to the action of the water, 

 and not to any merely physical cause, is proved by the fact that 

 alcohol does not occasion them. Quantitative experiments were 

 instituted with acetate of copper and Sulphocyanide of iron, to deter- 

 mine whether the effect of successive additions of water is in a 

 decreasing ratio. It was found to be so on the whole, but the 



