G52 MERCURY. 



monia, and to become black. Exposed to air the compound 

 loses its ammonia, and the subchloride of mercury recovers its 

 white colour. This ammoniacal compound is 2Hg 2 C1 + NH 3 . 

 When calomel is digested in solution of ammonia, it becomes 

 black, and was found by Dr. Kane to be converted into a 

 double subamide and subchloride of mercury, a portion of sal 

 ammoniac being dissolved by the water at the same time : 



2Hg 2 Cl and 2NH 3 = Hg 2 Cl + Hg 2 NH 2 and NH 4 , Cl. 



This compound is not altered by boiling water ; when quite dry, 

 it is of a grey colour. 



Subbromide of mercury, Hg 2 Br, is a white insoluble pow- 

 der, resembling in all respects the subchloride, and formed in 

 similar circumstances. A boiling solution of chloride of stron- 

 tium was found by Loewig to dissolve 3 equivalents of calomel, 

 of which 1 eq. precipitated, during the cooling of the solution. 

 When the filtered solution was evaporated, it deposited a salt 

 in small crystals, Sr Br + 2Hg 2 Br. These crystals were decom- 

 posed by pure water, and resolved into the insoluble subbro- 

 mide Hg 2 Br, and a double salt which dissolved easily and cry- 

 stallized by evaporation, Sr Br 4 Hg 2 Br. 



Subiodide of mercury, Hg 2 I, is obtained by precipitation as 

 a green powder, which is red when heated. It is also formed 

 by triturating mercury and iodine together in a mortar, with a 

 few drops of alcohol, in the proportion of 2 eq. of the former to 

 1 eq. of the latter. Another iodide of mercury was obtained by 

 Boullay, by precipitating nitrate of suboxide of mercury with a 

 solution of iodide of potassium, to which half an equivalent of 

 iodine had been previously added. It is a yellow powder, 

 which may be washed with alcohol ; from its composition it ap- 

 pears to be a compound of single equivalents of neutral iodide 

 and subiodide of mercury, Hg I + Hg 2 I. 



No subcyanide of mercury exists, and it is doubtful whether a 

 subfluoride, corresponding with the suboxide has been formed. 



Carbonate of black oxide of mercury, Hg O 2 , CO 2 , precipi- 

 tates as a white powder, when an alkaline carbonate is added 

 to the nitrate of the same oxide. The precipitate becomes grey 

 when the liquid containing it is boiled, and carbonic acid es- 

 capes. This carbonate is soluble both in carbonic acid water, 

 and in an excess of alkaline carbonate. 



