It is remarkable that neither the green nor the yellow oxides of iron, even when recently precipitated and not dried, seems capable of decomposing quadrisulphuret of lime. It is probable that trisulphuret and quadrisulphuret of iron may be formed; but I have not ascertained the truth of this opinion. 23. _Sulphurets of nickel._ _Protosulphuret._ According to Proust, nickel unites to sulphur by heat, so that 100 take 46 or 48; the sulphuret is of the colour of common pyrites. (Journ. de Physique, 63 and 80). According to Mr. Ed. Davy 100 nickel take 54 sulphur. By saturating a solution of nitrate of nickel with hydrosulphuret of lime I obtained 40 grains from 33 protoxide or 26 metal. This was evidently the protosulphuret; it was a fine black powder, and consists of 100 metal and 54 sulphur. _Quinsulphuret._ This compound may be obtained from nitrate of nickel and quadrisulphuret of lime, in the same manner as that of iron. It is a deep black powder, and consists of 100 nickel, and 215 sulphur. By exposure to heat, the greatest part of the sulphur burns off, and the rest may be expelled by an increase of temperature. Probably intermediate sulphurets may be formed; but I have not pursued the investigation. 24. _Sulphurets of tin._ Sulphur and tin unite both in the dry and humid way, and in various proportions. _Protosulphuret._ This may be readily formed in the dry way as follows; let 100 grains of tin be fused in a small iron ladle and heated to 6 or 8 hundred degrees Fahrenheit; let then small pieces of sulphur of 10 or 20 grains be successively dropped into the fused metal: a copious blue flame will instantly arise each time, and a glowing heat will take place, when the sulphur and tin are in contact; as soon as this ceases, another fragment of sulphur must be dropped in, and this two or three times repeated, heating it at last to a perfect red; the mass may then be taken out and pounded in a mortar; a great part of it will be a pulverulent powder, but some portions of malleable metal will still be mixed with it, which may be separated by a sieve. This must be again heated and treated with sulphur as before, and the whole mass will be converted to a sulphuret. I find that 100 parts of tin become in this way 127 grains; which is the due proportion of 52 tin and 14 sulphur, so that no loss of tin is sustained by the process when duly managed. According to Wenzel, 100 tin take 18 sulphur; Bergman, 25; Pelletier, 15 to 20; Proust, 20; but Dr. John Davy and Berzelius find nearly 27 as above stated, and I have no doubt it is near the truth. The protosulphuret of tin is a dark grey shining powder, with a streak like molybdena or plumbago; it is not much different in colour and appearance from native sulphuret of antimony, only less blue. It is soluble in muriatic acid by heat, and yields sulphuretted hydrogen and protomuriate of tin.