RESEARCHES ON THE AMMONIAC AL COMPOUNDS, 99 
Professor Kane in the preparation of this article for analy- 
sis, appears to have exercised every requisite caution to obtain 
a preparation which should give accurate results. The pro- 
cess adopted was to add to a cold solution of bichloride of mer- 
cury, a slight excess of water of ammonia ; the whole was then 
thrown on a filter, and the liquor allowed to drain away as 
much as possible ; then distilled water was poured over the 
precipitate, so as to remove entirely the whole of the original 
liquor, the use of any excess being carefully avoided, lest any 
decomposition should be produced, a fact which would be evin- 
ced by the injury of the pure milk white color of the preci- 
pitate. 
The preparation thus obtained is perfectly white, and is in- 
soluble in water without decomposition. When washed with 
a large quantity of cold, or a smaller quantity of hot water, or 
boiled in this liquid for a few moments, it is decomposed, and a 
heavy powder, of a canary yellow color results, which, when 
dry, presents a granular appearance. If potassa or soda be ad- 
ded to the liquid and boiled, the same decomposition results, 
the products being the same as when water is used, the purity 
of the yellow color alone being injured by the use of the alkali. 
When the alkali itself is mixed with the white precipitate, the 
same yellow color is produced, and ammonia is disengaged, 
but not more than one half of the ammonia can be liberated by 
this alkali. White precipitate dissolves readily in nitric and 
hydrochloric acids, from which solutions it is not again pre- 
cipitated by the addition of ammonia. These same solutions 
are probably formed when nitrate or hydrochlorate of ammo- 
nia is digested on the peroxide of mercury, when, according 
to the experiments of Messrs. Brett and Thompson, solution 
of the oxide takes place with the disengagement of ammonia. 
From the solution in hydrochloric acid, the iodide of potas- 
sium throws down a red powder, which is the periodide of 
mercury, and the sulphuret of barium, a black precipitate of the 
persulphuret of mercury, while, in the former instance, the 
hydrochlorate of ammonia and chloride of potassium remains 
in solution. A similar reaction takes place when the solutions 
