Element Cobalt, Co, Transition Metal. Have been known for millennia. Glass ingots have been recovered from Egyptian ancientries such as jar dating to the 15. , in coloring of which cobalt salts. Had been used, as well as in the cobalt. Ancient Assyrians and Babylonians used to produce blue paints which were used for ceramics glazing. Contained sapphire was the initial material from which the names of blue paints came.

Element Iridium, Ir, Transition Metal. Syssertskite, platinum, rhodium and ruthenium nevyanskite and aurosmirid. They contain also several other mineral forming elements and belong to the solid solutions class.

Element Iron, Fe Ferrum, Transition Metal. In the heat essentially compounds of the formula Fe. Are formed; in the cold, iron hydroxide, Fe.

Element Manganese, Mn, Transition Metal. The element manganese is very closely related to iron. It differs from it in being more readily oxidised, and in its higher compounds being more readily formed than in the case of iron. For the rest, the corresponding compounds of manganese and iron are very similar to one another, and in many cases are isomorphous. In nature, manganese occurs very widely distributed, but is much less abundant than iron. It is found chiefly as manganese peroxide, Mn.

Element Rhodium, Rh, Transition Metal. Was discovered in 1803 by William Hyde Wollaston, soon after his discovery of palladium. Wollaston dissolved raw platinum in aqua regia. The acid surplus was neutralized by caustic soda. He then precipitated the platinum by adding ammonium chloride, NH. Cl; palladium was removed as palladium cyanide after treating the solution with mercuric cyanide.

Element Osmium, Os, Transition Metal. About the same time, Collet-Descotils suspected the existence of a new metal by the black powder formed by the dissolution of native platinum in aqua regia. The residue itself named osmiridium.

Element Rhenium, Re, Transition Metal. Is the rarest and much dispersed trace element. Its average abundance is 7x10. Is the rarest element with stale isotopes.