SIL VERMERCUR Y. 



343 



tions formed when copper, silver, zinc, etc., salts are dissolved in am- 

 monia water. The former are all insoluble in water. 



Ammoniated mercury is a white, tasteless, insoluble powder. 



Mercurous salts with ammonia water give black insoluble precipi- 

 tates consisting of a mixture of mercuric-ammonium salts and mercury, 

 which causes the black appearance. For mercurous chloride and 

 nitrate the reactions are : 



2HgCl + 2NH 3 = HgNH 2 .Cl -f Hg -f NH 4 C1. 

 2HgN0 3 -f 2NH 3 = HgNH 2 .N0 3 + Hg + NH 4 NO 3 . 



It should be noted that in the case of mercury salts, ammonia water 

 does not precipitate hydroxides, as it does in other cases. 



Tests for mercury. 



Mercurous salts. 



(Mercurous nitrate, HgNO 3 may 

 be used. ) 



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. 

 2HgN0 3 -f H a S = 

 2HN0 3 + HgS + Hg. 



Green precipitate of mercurous 

 iodide (Plate IV., 7): 



KN0 3 + Hgl. 



Dark-brown precipitate of mer 

 curous oxide, Hg 2 O (Plate 

 IV., 5). 



Black precipitate of a mixture 

 of mercury and mercuric-am- 

 monium chloride (see expla- 

 nation above). 



Yellowish precipitate of mer- 

 curous carbonate, which is 

 unstable. 



White precipitate of mercurous 

 chloride is produced : 

 HgN0 3 + HC1 = 

 HN0 3 -f- HgCl. 



Mercuric salts. 



(Mercuric chloride, HgCl 2 , may 

 be used.) 



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 carb., mixed 

 with mercuric oxychloride. 



No change. 



7. Stannous- chloride produces, in solutions of mercury, a white 

 precipitate, which turns dark-gray on heating with an excess of the 

 reagent. The reaction is due to the strong reducing or deoxidizing 

 property of the stannous chloride, which itself is converted into stannic 

 chloride, while the mercury salt is first converted into a mercurous 

 salt and afterward into metallic mercury : 



2HgCl 2 + SnCl 2 = 2HgCl -f SnCl 4 ; 

 2HgCl + SnCl 2 = 2Hg + SnCl,. 



