MERCURIC NITRATES. 663 



to produce effects in medicine analogous to those of a root 

 formerly employed, and known as convolvulus turpethum. 

 The composition of turbith mineral is HgO, SO 3 +2HgO 

 (Kane). Solution of ammonia converts both the neutral sul- 

 phate and turbith mineral into a heavy powder, which Dr. Kane 

 names ammonio- turbith, and finds to be HgO, SO 3 -f Fig, NH 2 + 

 2HgO. It is, therefore, analogous in composition to the yellow 

 powder produced by the decomposition of white precipitate. 



Nitrates of the red oxide of mercury, Mercuric nitrates. 

 The neutral nitrate cannot be crystallized, but it exists in 

 solution, when chloride of mercury is precipitated by nitrate of 

 silver. When red oxide of mercury is dissolved in nitric acid, 

 or when the metal is dissolved in the same acid with ebullition, 

 till a drop of the solution no longer occasions a precipitate in 

 water containing a soluble chloride, a subriitrate is formed 

 crystallizing in small prisms, which are deliquescent in damp 

 air. Its composition is expressed by Hg O, NO 5 + HgO +2HO. 

 It is the only crystallizable nitrate of this oxide. Decomposed 

 by water, this salt yields yellow subnitrate, which when washed 

 in its preparation by warm, but not boiling water, is HO, NO 5 

 + 3 HgO. When the subnitrate is prepared by boiling water, it 

 has a red colour, and probably consists of NO 5 + 6Hg O (Kane). 



Nitrate of mercury aifords several compounds when treated 

 with ammonia. When a dilute, and not very acid solution of 

 that salt is treated in the cold, by weak water of ammonia 

 not added in excess, a pure milk-white precipitate appears, 

 which is not granular, and remains suspended in the liquid 

 for a considerable time. It was analyzed by G. Mitscherlich, 

 and to distinguish it from some other salts containing the same 

 constituents, I shall name it Mitscherlich 's ammonia subnitrate. 

 It contains NO 5 , 3HgO and NH 3 , which Dr. Kane would arrange 

 thus, NH 3 , NO 5 + 3HgO, making the ammonia or amide of 

 hydrogen basic to the acid. The preceding compound is altered 

 in its appearance by boiling water, and becomes much heavier 

 and more granular forming Soubeiran's ammonia subnitrate, the 

 composition of which Dr. Kane finds to be HgO, NO 3 + Hg, 

 NH 2 + 2HgO; or it resembles in constitution the bodies already 

 described containing chlorine and sulphuric acid. The yellow 

 crystalline ammonia subnitrate, a third compound, was obtained 

 by G. Mitscherlich by boiling the ammonia subnitrate with an 

 excess of ammonia, and adding nitrate of ammonia by which a 



