202 



METALS AND THEIR COMBINATIONS. 



known as red sulphide of mercury, cinnabar, or vermilion. It forms 

 brilliant dark-red crystalline masses, or a fine bright scarlet powder, 

 which is insoluble in water, hydrochloric or nitric acid, but soluble 

 in nitro-hydrochloric acid. 



Mercuric and rnercurous sulphides may be made also by triturating 

 the elements mercury and sulphur in the proper proportions, when 

 they combine directly. 



Ammoniated mercury, Hydrargyrum ammoniatum, 

 = 251.2 ( White precipitate. Mercuric-ammonium chloride). This com- 

 pound is made by pouring solution of mercuric chloride into water of 

 ammonia, when a white precipitate falls, which is washed with highly 

 diluted ammonia water and dried at a low temperature : 

 HgCl 2 + 2NH 4 OH 4= NH 2 HgCl + NH 4 C1 + 2H 2 O. 



As shown by the composition of this compound, it may be re- 

 garded as ammonium chloride, NH 4 C1, in which two atoms of hydro- 

 gen have been replaced by one atom of the bivalent mercury. (There 

 are many compounds known in which metallic atoms replace hydrogen 

 in salts of ammonium ; the ammonium copper compounds belong to 

 this group of substances.) 



Ammoniated mercury is a white, tasteless, insoluble powder. 



Analytical reactions. 



Mercurous salts. 



(Mercurous nitrate, Hg 2 (No 3 ) 2 may 

 be used.) 



Mercuric salts. 

 (Mercuric chloride, HgCl 2 , may 



1. Hydrogen sul- 

 phide, or ammo- 

 nium sulphide. 



2. Potassium iodide 



3. Potassium or so- 

 dium hydroxide. 



4. Ammonium hy- 

 droxide. 



5. Potassium or so- 

 dium carbonate. 



6. Hydrochloric 

 acid or soluble 

 chlorides. 



Black precipitate of mercuric 

 sulphide, with mercury. 

 Hff.(NO t ), + H 2 S = 

 2HN0 3 + HgS + Hg. 



Green precipitate of mercurous 

 iodide (Plate IV., 7): 

 Hg 2 (N0 3 ) 2 + 2KI = 

 2KN0 3 + Hg 2 I 2 . 

 Dark -brown precipitate of mer 

 curous oxide, Hg 2 O (Plate 

 IV., 5). 



Black precipitate of mercurous 

 ammonium salt is formed. 

 (The insoluble white calomel 

 is converted into a black 

 powder.) 



Yellowish precipitate of mer- 

 curous carbonate, which is 

 unstable. 



White precipitate of mercurous 

 chloride is produced : 



Hg 2 (N0 3 ) 2 -f2HCl = 

 2HN0 3 + Hg 2 Cl 2 . 



Black precipitate of mercuric 

 sulphide. (Precipitate may be 

 white or gray, with an insuffi- 

 cient quantity of the reagent.) 

 (See above ) (Plate IV., 1.) 



Red precipitate of mercuric 

 iodide (See above.) (Plate 

 IV., 6.) 



Yellow precipitate of mercuric 



oxide HgO. (See above.) 



(Plate IV., 3.) 

 White precipitate of a mercuric 



ammonium salt is formed. 



(See explanation above.) 



Brownish-red precipitate of 

 basic mercuric carbonate. 

 HgC0 3 .3HgO. 



No change 



