CHLORIDE OF MERCURY. 659 



compound of chloride and sulphuret of mercury. This sub- 

 stance is changed entirely into sulphuret of mercury, when left 

 in water containing sulphuretted hydrogen. On the other hand, 

 precipitated sulphuret of mercury digested in a solution of chlo- 

 ride of mercury, takes down that salt and forms the compound 

 in question. Sulphuret of mercury combines likewise with the 

 bromide, iodide, fluoride and nitrate of mercury, and always in 

 the proportion of two atoms of the sulphuret to one atom of the 

 other salt. 



Double salts of chloride of mercury. Chloride of mercury was 

 found by M. Bonsdorff to combine with chloride of potassium in 

 three different proportions, forming a series of salts in which the 

 chloride of potassium remains as one equivalent, while the chloride 

 of mercury goes on increasing. They are, KCl-fHgCl + HO, 

 which crystallizes in large transparent rhomboidal prisms ; KC1 

 + 2HgCl + 2HO crystallizing in fine needle-like amianthus; 

 and KCl + 4Hg C1 + 4HO, which crystallizes also in fine needles. 

 Chloride of sodium forms only one compound, Na C1 + 

 2Hg CI + 4HO which crystallizes in fine regular hexahedral 

 prisms. One of the double salts of chloride of ammonium has 

 long been known as sal alembroth. It crystallizes in flattened 

 rhomboidal prisms, NH 4 Cl + Hg Ci + HO, and is isomor- 

 phous with the corresponding potash salt. It loses the 

 water it contains in dry air, without change of form. Dr. 

 Kane has also obtained NH 4 Cl + 2Hg Cl, and the same 

 with an atom of water, NH 4 Cl + 2Hg Cl + HO, the first 

 in a rhomboidal form, and the second in long silky needles. 

 All these double chlorides are obtained by dissolving 

 their constituent salts together in the proper proportions. 

 Chlorides of barium and strontium form compounds in 

 good crystals with chloride of mercury, Ba Cl + 2Hg Cl-f- 4 HO, 

 and Sr Cl + 2Hg Cl-f 2HO. Chloride of calcium combines 

 in two proportions with the mercurial chloride. When chlo- 

 ride of mercury is dissolved to saturation in chloride of cal- 

 cium, tetrahedral crystals separate from the solution, which are 

 pretty persistent in air, Ca Cl-f 5Hg C1 + 8IIO. After the 

 deposition of these crystals, the liquid affords, when evaporated 

 by a gentle heat, a second crop of large prismatic crystals, Ca Cl 

 4- 2Hg Cl + 6IIO, which are very deliquescent. Chloride of mag- 

 nesium also forms two salts, Mg Cl + 3Hg Cl + HO, and Mg Cl 

 -fHgCH-GHO, both deliquescent. Chloride of nickel gives 



