_Deutosulphuret._ Dr. Thomson mentions a natural production or species of galena which contains twice the quantity of sulphur of that above. I have reason to believe that this compound is easily formed in the humid way, by treating the precipitated oxide with the due quantity of quadrisulphuret of lime. _Trisulphuret_ and _quadrisulphuret_. These compounds, I find, may be formed by means of quadrisulphuret of lime or potash. When a solution of any salt of lead or the recently precipitated and moist oxide, is treated with the requisite quantity of quadrisulphuret of lime, a combination consisting of 1 atom of lead and 3 of sulphur is formed. It is a black powder not differing much in appearance from the protosulphuret; it is lighter and more spongy. It consists of 100 lead and 46 or 47 sulphur. The due proportions of the elements to form the above compound are, lead 100 parts in solution, and sulphur, 62 parts; ¼ of the sulphur is retained by the lime, and may be converted into sulphuric acid instantly by the addition of as much oxymuriate of lime as contains oxygen equal in weight to the sulphur, as it has already as much oxygen as converts it into sulphurous oxide, derived from the oxide of lead. Quadrisulphuret of lead is to be obtained in the same way; only we must have an excess of the sulphuret of lime, or more than 80 sulphur for 100 lead in solution, as ⅕ part of the sulphur at least is retained by the lime. The quadrisulphuret is a black powder like the others; it burns with a blue flame and loses nearly 40 per cent., the residue being still black. It consists of 100 lead and 62 sulphur. I have not ascertained whether any higher sulphuret of lead is capable of being formed this way. It has been already noticed (page 109), that a beautiful white, silvery sulphuretted sulphite of lead is formed and gradually precipitated, when nitrate of lead is dropped into a solution where as much black quadrisulphuret of lead has been just thrown down as the sulphuret of lime can form. 26. _Sulphurets of zinc._ Zinc and sulphur are scarcely to be united directly by heat; but by heating the oxide of zinc and sulphur together, a combination is effected; part of the sulphur carries off the oxygen in sulphurous acid, and part combines with the zinc. Mineralogists give the name of _blende_ to a mineral which is chiefly the protosulphuret of zinc: its colour is yellowish, brown, or black almost like galena: its specific gravity is usually 3.9 or 4. _Protosulphuret._ The above artificial compound, or the mineral, may be taken as examples of the union of 1 atom zinc and 1 sulphur. But the most correct and convenient way of forming it for the purpose of chemical investigation is, to drop a given portion of some salt of zinc into a dilute hydrosulphuret. A white precipitate falls, which when dried becomes a dark cream colour. It is found to consist of 2 parts zinc and 1 of sulphur nearly; that is, of 29 parts zinc and 14 sulphur.