| Subsulphuret, | 100 | platina | + | 19 | sulphur |
| Sulphuret, | 100 | —— | + | 28.2 | —— |
| Supersulphuret, | 100 | —— | + | 38.8 | —— |
I have obtained the sulphuret of platina in five ways: 1st. By pouring sulphuret of lime solution by degrees into muriate of platina, and agitating the mixture well or till it grew black each time; after digesting for some days, repeated filtering, and drying, a black powder is obtained: 2. Instead of sulphuret, hydrosulphuret of lime was used; the precipitate was obtained under like circumstances: 3d. Sulphuretted hydrogen water was used, and the precipitate obtained in like manner: 4th. Ten grains of ammonia-muriate of platina were treated with sulphuretted hydrogen water; by continued agitation the yellow powder disappeared, the liquid looked uniformly black, and at length a precipitate was formed; by repeated filtration and addition of sulphuretted hydrogen water, the whole of the platina was thrown down, and the liquid remained colourless; but it is difficult to discover the exact quantity of sulphuretted hydrogen requisite for any weight of the ammonia-muriate from the tediousness of the operation; 6 grains of well dried black powder were obtained, besides perhaps 1 grain of loss on the filters: 5th. Ammonia-muriate of platina was heated in a covered crucible along with sulphur till it was judged that all the uncombined sulphur was sublimed or dissipated.
All these sulphurets appear to me to be the same when dried in a moderate heat. When exposed to a low red heat they yield water and sulphurous acid, and lose about ⅖ of their weight.
The subject however, requires further investigation. The sulphurets of platina appear of a complex nature, and the proportions of their elements are not yet determined with precision.
15. Sulphurets of silver.
Silver combines with sulphur in two different proportions, and forms two sulphurets, both of them black or dark brown.
1. Protosulphuret of silver. This may be formed either by the dry or humid way: if thin lamina of silver be heated with sulphur, they combine and form this sulphuret; a higher degree of heat expels the sulphur again. It is formed too by passing sulphuretted hydrogen or a hydrosulphuret through a solution of silver in nitric or other acids. The atom of silver unites with that of sulphur, whilst the hydrogen unites with the oxygen. Of course this compound is composed of 90 silver, and 14 sulphur, and the atom weighs 104; or 100 silver unite with 15.5 sulphur. Klaproth finds 100 silver and 17.6 sulphur; Wenzel 100 silver, and 14.7 sulphur; Berzelius 100 silver, and 14.9 sulphur; and Vauquelin 100 silver, and 14 sulphur.
Trisulphuret of silver. This compound is formed whenever neutral nitrate of silver is dropped into a solution of quadrisulphuret of lime or alkali. Mutual saturation seems to take place when eight atoms of nitrate meet with seven of quadrisulphuret. Trisulphuret of silver is constituted of 90 silver, and 42 sulphur; or of 100 silver, and 46.5 sulphur. Its colour is not so dark as that of the protosulphuret. The residuary liquid contains sulphurous acid, which is easily converted into sulphuric by the addition of a portion of lime; and the quantity of acid may then be determined by muriate of barytes.
16. Sulphurets of mercury.
Mercury combines readily with sulphur both in the dry and humid way, and that in several proportions, as under: namely,