CHLORIDE OF MERCURY. fj~>5 



powder forms the lively red pigment, vermilion. This sulphuret 

 is hlack before sublimation. It is precipitated black also when 

 sulphuretted hydrogen is sent through a solution of corrosive 

 sublimate ; but is of the same composition in both states. The 

 sulphuret of mercury, however, may be obtained of a red colour 

 without sublimation, or in the humid way, by several methods. 



Liebig recommends for this purpose to moisten the prepara- 

 tion called white precipitate, recently prepared, with the 

 sulphuret of ammonium, and allow them to digest together. 

 The black sulphuret is instantly produced, which in a few 

 minutes passes into a fine red cinnabar, the colour of which is 

 improved by digesting it at a gentle heat in a strong solution of 

 hydrate of potash. The sulphuret of ammonium used in this 

 experiment is prepared by dissolving sulphur in hydrosul- 

 phuret of ammonia to saturation. Cinnabar is not attacked by 

 sulphuric, nitric or hydrochloric acid, nor by solutions of the 

 alkalies, but it is dissolved by aqua regia. 



Chloride of mercury, Corrosive sublimate, 1708.5 or 136.9. 

 This salt may be formed by dissolving red oxide of mercury 

 in hydrochloric acid, or by adding hydrochloric acid to any 

 soluble salt of that oxide, but it is generally prepared in a dif- 

 ferent manner. Four parts of mercury are added to five parts 

 of sulphuric acid, and the mixture boiled till it is converted 

 into a dry saline mass. The mercuric sulphate thus obtained 

 is mixed with an equal weight of common salt, and heated 

 strongly in a retort by a sand bath ; chloride of mercury sub- 

 limes and condenses in the upper part and neck of the retort, 

 while sulphate of soda remains behind with the excess of 

 chloride of sodium. The mercury and sodium have exchanged 

 places in the salts : 



Na Cl and Hg O, SO 3 = Hg Cl and Na O, SO 3 . 



Mercury, when heated in a stream of chlorine gas, burns with 

 a pale flame, and is converted into a white sublimate of chloride. 

 The salt has been prepared on a large scale in this manner, 

 which was suggested as a manufacturing process by Dr. A. T. 

 Thomson. 



The sublimed chloride of mercury forms a crystalline mass, 

 of which the density is 6.5 ; it fuses at 509, and boils about 

 563. , The vapour of chloride of mercury is colourless, its den- 

 sity 9420, 1 volume of it containing I volume of mercury vapour 



u u 



