4'28 Mr. Thomas Richardson on Donium, a 



tity of a dark brown flocky matter. This being supposed 

 to be iron, was separated by a filter. 



The caustic soda solution was saturated with muriatic 

 acid, and the white matter again thrown down, by carbo- 

 nate of soda. This precipitate was also collected on a filter, 

 and during the washing, the colour changed to brown. 



The brown matter, insoluble in caustic soda, which was 

 supposed to be peroxide of iron, was dissolved in muriatic 

 acid. Caustic ammonia being added, a white precipitate 

 appeared, which was completely dissolved in an excess of 

 the precipitant. 



There were several circumstances in this analysis, which 

 appeared to indicate that the mineral contained some other 

 base besides alumina. The striking solubility of the first 

 precipitate in caustic ammonia, showed that it could not 

 consist entirely of that earth ; while the remarkable fact, 

 that all the precipitates, though at first white, became 

 brown during the washing, rendered it probable, that they 

 all contained at least a portion of the same substance. 



From these peculiarities, it was considered necessary to 

 repeat the analysis on a larger scale ; and in order to fix 

 upon a method of proceeding with it, a few experiments 

 were made, to determine if possible, the nature of the 

 constituents. For this purpose, a portion of the brown 

 matter was dissolved in muriatic acid, and the solution 

 rendered as neutral as possible, by evaporation. The pro- 

 perties observed were the following :— 



1. When a current of sulphuretted hydrogen gas was 

 passed through the solution, previously rendered slightly 

 acid, a light brown precipitate appeared. 



2. When an excess of caustic ammonia was added to 

 the solution, through which the sulphuretted hydrogen had 

 been passed, the precipitate became much more dense, and 

 of a dark green colour. 



3. When caustic soda was added to the solution, a white 

 flocky precipitate appeared, which was readily dissolved in 

 an excess of the precipitant. 



4. Caustic ammonia also threw down a white precipitate, 

 equally soluble in an excess of the alkali. 



5. Carbonate of ammonia acted in the same way. 

 These characters rendered it perfectly evident, that this 



