4. _Sulphur and Cadmium._--Three compressions give a yellowish-gray homogeneous mass. The powder is yellow, but less pure than that of cadmium sulphide obtained by precipitation. Strong hydrochloric acid dissolves the mass with escape of hydrogen sulphide. 5. _Sulphur and Aluminum._--Result incomplete. After five compressions a mass is obtained which, in contact with moist air, gives off an odor of hydrogen polysulphide. 6. _Sulphur and Bismuth._--The combination takes place with great ease. 7. _Sulphur and Lead._--The combination is still more easy. 8. _Sulphur and Silver._--The action is slow; eight compressions are necessary. 9. _Sulphur and Copper._--Three compressions complete the combination. When the product of the compression is heated, there is no development of heat or light. 10. _Sulphur and Tin._--Three compressions give a block which yields a yellowish-gray powder, easily soluble in a hot solution of sodium sulphide. Stannic sulphide is therefore formed by the compression of sulphur and tin. 11. _Sulphur and Antimony._--After two compressions we obtain a gray-black mass having the color and luster of stibine. When powdered it dissolves with ease in hot hydrochloric acid, giving off hydrogen sulphide. 12. _Sulphur and Red Phosphorus; Sulphur and Carbon._--Result entirely _nil_; there is produced not the least trace of phosphorus sulphide nor of carbon sulphide. CONCLUSIONS TO BE DRAWN FROM THESE FACTS. The negative results just mentioned have an especial interest. It is established that red phosphorus has a higher specific gravity than white phosphorus, that of the former being 1.96, and that of the latter 1.82. The author's former researches (_Bulletins de l'Académie Royale de Belgique_, 49, p. 323, 1880) have shown that if sufficient pressure is applied to a body capable of assuming several allotropic states, it takes under pressure the state corresponding to its greatest density. It is consequently impossible to transform red phosphorus into white phosphorus by pressure. But we know, on the other hand, that red sulphur and red phosphorus may be mixed with impunity at common temperatures without combination ensuing; to produce combination the temperature must be raised to about 260°, the point of transformation of red phosphorus into white phosphorus. It is thus established that red phosphorus must first be changed from its allotropic condition before entering into combination with sulphur. The pressure opposing this change renders also the act of combination impossible; red phosphorus appears to us like a body which has lost its chemical faculties.