Platinum is a chemical element, whose elemental substance is commonly known as platinum and belongs to the platinum element system. Its chemical symbol Pt is one of precious metals. Atomic weight 195.078, slightly less than that of gold, atomic number 78, is a transition metal. Melting point 1772 ℃, boiling point 3827 + 100 ℃, the density of 21.45 g/cm 3 (20 ℃), soft, good ductility, thermal conductivity and electrical conductivity. As a gray spongy substance, sponge platinum has a large specific surface area and has a strong absorption capacity for gases (especially hydrogen, oxygen and carbon monoxide). Powdered platinum black absorbs large amounts of hydrogen. Platinum chemical inertness, stable in air and humid environment, lower than 450 ℃ when heated, the surface oxide platinum thin film, high temperature can react with sulfur, phosphorus, halogen. Platinum is insoluble in hydrochloric acid, sulfuric acid, nitric acid and alkali solutions, but soluble in royal water and molten alkali.
Although wang shui can dissolve platinum, it is related to the state of platinum. Dense platinum dissolves very slowly in normal temperature, and it takes 4-5 hours for the platinum wire with a diameter of 1 mm to fully dissolve. Platinum black (platinum powder) can react with concentrated sulfuric acid when heated to form Pt(SO4)2, SO2 and water. Chloroplatinic acid is made by dissolution of platinum into royal water. The product of this reaction is H2PtCl6, not the previously thought nitrogen-platinum compound. Chloroplatinic acid is a red-brown solid that can be obtained by vaporizing its solution.
Platinum base containing iridium binary alloy, high temperature for the continuous solid solution, slow cooling to solid phase decomposition during 975 ~ 700 ℃ and the phase equilibrium process slowly. Iridium is volatile and oxidized, which can significantly improve the corrosion resistance of platinum. The alloy has high hardness, high melting point, high corrosion resistance and low contact resistance.
With platinum based binary alloy containing silver, at 1185 ℃ and 45% Ag peritectic reaction. The low alloy high strength, good elasticity and elastic aftereffect, resistance coefficient, low thermoelectric potential and heat resistance, corrosion resistance, no magnetic, stable performance, platinum, silver alloy smelting and processing is very difficult, high frequency induction heating furnace of hydrogen is commonly used in protection of smelting, casting must be after homogenization, processed into plate and wire, etc.
