656 MERCURY. 



and 1 volume of chlorine gas. This salt is soluble in 16 parts 

 of cold and in 3 parts of boiling water, in 2J parts of cold and 

 in I part of boiling alcohol, and in 3 parts of cold ether. It 

 is not decomposed by sulphuric or nitric acid ; is largely dis- 

 solved by the latter and also by hydrochloric acid. It is ob- 

 tained by sublimation and from solution, in two different crys- 

 talline forms. The solutions of chloride of mercury exposed to 

 the direct rays of the sun evolve oxygen, while hydrochloric acid 

 is dissolved and subchloride of mercury precipitates. The decom- 

 position of this salt, by the action of light, is greatly more rapid 

 when the solution contains organic matter. The poisonous 

 action of chloride of mercury, which is scarcely inferior to that 

 of arsenious acid, is best counteracted by liquid albumen, with 

 which chloride of mercury forms an insoluble and inert com- 

 pound. 



The solution of chloride of mercury affords a yellow or brown 

 precipitate with the hydrates of potash and soda, and with lime 

 water ; a black precipitate with sulphuretted hydrogen, and a 

 fine scarlet precipitate with iodide of potassium. Mercury is 

 thrown down from that solution by metallic copper. A drop 

 of the solution does not tarnish polished gold, but if the 

 moistened surface be touched by zinc or iron, mercury is im- 

 mediately precipitated, and produces a blue stain upon the 

 surface of the gold, while the common metal dissolves. 



Chloride of mercury and ammonia. When chloride of mer- 

 cury is gently heated in a stream of ammoniacal gas, the latter 

 is absorbed, and the compound fuses from heat evolved in the 

 combination. The product was found by Rose to contain half 

 an equivalent of chlorine, 2HgCl + NH 3 . This compound 

 boils at 590 and may be distilled without loss of ammonia; it 

 is decomposed by water. When the double chloride of mercury 

 and ammonium, called sal alembroth, is precipitated by potash 

 in the cold, a white powder is obtained, which was first dis- 

 tinguished by Wohler from the compound next described ; its 

 composition may be expressed, from the analysis of Dr. Kane, 

 by Hg Cl-f NH 3 . The same compound is also formed when 

 ammonia is added to a solution of sal ammoniac, and chloride of 

 mercury dropt into the liquid, brought to the boiling point, so 

 long as the precipitate which is produced is redissolved. The 

 compound appears on the cooling of the solution, in small 

 crystals, which are garnet dodekahedrons (Mitscherlich). The 



