Platinum is a heavy, greyish-white, highly malleable and ductile metallic element. It is resistant to the majority of chemicals, practically unoxidizable, except by the presence of bases. It is fusable only to extremely high temperatures (melting point 1,772º C). Platinum is used for making chemical and scientific apparatus, as a catalyst in the oxidation of ammonia to electric acid and in jewelry. It is found in nature free or in combination with other metals, such as osmiridium (osmium + iridium), nickel, and palladium. Symbol Pt; atomic weight 195.09; atomic number 78; valence 2, 3, 4.