Platinum Crucible, Features And Cleaning
Platinum crucible, also known as Pt crucible, which is often used in the laboratory because of its excellent properties. Platinum has a melting point of up to 1774 °C, making it chemically stable, neither undergo chemical changes after burning in air, nor absorb water. Most chemical agents have no erosive effect on platinum.
1. Features of Platinum:
Different from glass, porcelain and other common materials, platinum is resistant to the corrosion of hydrofluoric acid and molten alkali metal carbonates. So it is often used for precipitation ignition, hydrofluoric acid melting and carbonate melting. Platinum is slightly volatile at high temperatures and should be corrected after a long burn. Platinum of 100 cm2 area burning at 1200 °C for 1 hr will lose about 1 mg. Platinum is substantially nonvolatile at below 900 °C.
2. The use of platinum crucible should comply with the following rules
Platinum crucible cannot be in contact with any other metal when heated because platinum is easily alloyed with other metals at high temperatures. Therefore, the platinum crucible must be placed on a platinum tripod or burned on a support of ceramic, clay, quartz, etc., or it should be placed on a hot plate or an electric furnace with asbestos sheets, but not directly with an iron plate or an electric furnace. The clamp used should be covered with a platinum head, and nickel or stainless steel clamp can only be used at low temperatures (in case alloyed with).
3. Cleaning of Platinum crucible
If the platinum crucible has spots, it can be treated with hydrochloric acid separately (or nitric acid, do not mix). If ineffective, melt process the spotted platinum crucible in a platinum vessel at a relatively low temperature for 5 to 10 minutes with potassium pyrosulfate, pour out the molten materials, and then use hydrochloric acid to treat the spotted platinum crucible. If it is still ineffective, try again with sodium carbonate melt treatment. It can also be gently rubbed with wet fine sand (passing through a 100 mesh sieve, ie 0.14 mm mesh, it will lead to slight platinum lose).