Vauquelin heated 100 parts of the triple salt of palladium with an equal weight of sulphur, and obtained 52 parts of a blueish white sulphuret, very hard, and when broken exhibiting brilliant plates in its fracture. He had previously found that 100 salt contained 40 to 42 of metal: hence 100 metal combined with from 24 to 30 of sulphur. This agrees nearly with the above results of Berzelius. A very high degree of heat expels the sulphur and oxidizes the metal; but a more moderate heat leaves the palladium of a silver white colour and nearly pure. According to this the atom of protosulphuret of palladium must consist of 50 palladium, and 14 sulphur. 18. _Sulphuret of rhodium._ Vauquelin found that 4 parts of the ammonia-muriate of rhodium (containing 28 or 29 per cent. of metal) being mixed with an equal weight of sulphur, and heated, a blueish white button was obtained, weighing 1.4. Hence 100 metal seem to take 25 of sulphur; and allowing this to be the protosulphuret of rhodium, the atom must consist of one rhodium 56, and one sulphur 14, making the whole weight 70. 19. _Sulphuret of iridium._ According to Vauquelin, 100 parts of the ammonia-muriate of iridium heated with as much sulphur, yield 60 parts of black powder resembling the other metallic sulphurets; but 100 parts of the salt were found to yield from 42 to 45 of metal. Now supposing the last number the most correct, it should seem that 3 parts iridium take 1 sulphur, or 100 take 33⅓. This being supposed the protosulphuret, the atom of iridium must be 42, and that of the sulphuret 56. 20. _Sulphuret of osmium._ It is as yet unknown whether any combination of sulphur and osmium exists. 21. _Sulphurets of copper._ Copper readily unites with sulphur both in the dry and humid way. When 3 parts of copper filings are mixed with 1 part of sulphur, and heat applied, a brilliant combustion ensues, which indicates the union of the two bodies. Copper leaf burns in the fumes of sulphur, as Berzelius has observed, with great brilliancy. The protosulphuret of copper obtained by these similar methods, when pulverized, is black or dark coloured; it has been analyzed by various authors, who nearly agree in their results. Proust finds 100 copper unite with 28 sulphur; Wenzel, 100 copper and 25 sulphur; Vauquelin, 100 copper and 27 sulphur; and Berzelius 100 copper and 25 sulphur. If the atom of copper be 56, and that of sulphur 14, the atom of protosulphuret of copper will be 70; which gives just 100 copper and 25 sulphur. The protosulphuret may also be formed in the humid way, by sending sulphuretted hydrogen gas or a hydrosulphuret into a solution of protomuriate of copper, or amongst the recently precipitated protoxide of copper.