Several common methods for identifying platinum
Visual inspection method:
Marking: Each piece of jewelry must be engraved with chemical composition marks, such as (pt900)(pt750). All stamps that begin with "pt" are platinum ornaments: platinum is tin white, that is, white with gray and bright luster.
Instrument testing:
Hardness test: the hardness of platinum is 4-4.5 degrees, which is harder than gold and silver. It is scratched with a knife or glass, but it will not be scratched by nails. Density measurement: Platinum has a very high density, which makes it feel heavy. The density measured by hydrostatic pressure method should be 265,438+0.43 g/cm. The melting point of platinum is as high as 1.773 degrees. Put platinum in the wine. Insoluble in ordinary acid, scrape platinum on the touchstone, drop hydrochloric acid, and try with hydrogen peroxide: take a little platinum powder and put it in a hydrogen peroxide bottle, and hydrogen peroxide will immediately generate bubbles. After the reaction, platinum is harmless and can be used.
Hand balance method:
The density of platinum reaches 2 1.45. Through the weighing test of the same volume of materials, platinum has a heavy feeling, which is heavier than gold (19.36), K- platinum and silver (10.45).
Combustion and melting methods:
The melting point of platinum reaches 1773oC, which is much higher than that of k platinum and silver. General welding guns can't melt platinum, so they can identify the authenticity. And that color of platinum doe not change after cool.
Marking method:
Platinum jewelry has a standard seal. Internationally expressed by PT or PT. For example, the purity of PT950 platinum is 950%.
Natural gas law:
Put the jewelry on the twisted gas burner and let it stand for a few minutes. If the jewelry turns red and heats up to light the gas stove, it is platinum products. This is because platinum can be used as a catalyst to promote the oxidation and heat release of gas and air, and make platinum turn red, thus igniting the gas.
Field test method:
A put mercury on platinum, platinum will not be polluted, and the combination of gold, silver and mercury will be polluted. B. Put some powder in the hydrogen peroxide bottle with a file at the edge or middle depression of platinum jewelry. Platinum can be used as a catalyst to promote the decomposition of hydrogen peroxide and release oxygen to churn up and down.
Platinum jewelry usually expresses the texture of jewelry with a few thousandths of platinum, which is also one of the basis for jewelry pricing.
Weighing:
The specific gravity of platinum is 2 1.4, and that of silver is 10.49. The same volume of platinum is twice as heavy as silver, and you can tell them apart by weighing them by hand.
Comparison of appearance and hardness:
When platinum is carefully observed with the naked eye, it will be slightly gray, bright white and hard. It is difficult to scratch with a pin, and its Mohs hardness is 4.3, while silver is white, smooth and delicate, and will turn gray or black when slightly oxidized. Its Mohs hardness is 2.7, which is much softer than platinum.
Combustion method:
Platinum can resist high-temperature oxidation, with a melting point as high as 1770oC, and it will not melt when burned with ordinary high-temperature (gasoline). After cooling, its color will remain unchanged or there will be quenching marks. On the other hand, the melting point of silver is very low. After high temperature combustion, its color is red, black or black depending on the silver content.
Chemical methods:
Platinum is extremely stable in chemical properties, resistant to corrosion, and does not react with any acid or alkali, while silver is not resistant to strong acid corrosion.
Extended data:
Platinum application
Of the .245 tons of platinum sold on 20 10,13 tons (46%) are used for automotive catalytic converters, 76 tons (3 1%) are used for jewelry, and the remaining 35.5 tons are used for investment, electrodes, anticancer drugs, oxygen sensors, spark plugs and turbines.
1, catalyst
The biggest use of platinum is as a catalyst for chemical reactions, usually platinum black. /kloc-at the beginning of the 0 th century, chemists began to use platinum powder to catalyze the ignition reaction of hydrogen. At present, platinum is widely used in catalytic converters of automobiles, so that unburned hydrocarbons with low concentration in exhaust gas are completely burned, and carbon dioxide and water vapor are produced. In petroleum industry, platinum can be used to catalyze several different reactions, especially the catalytic reforming of naphtha to produce high octane gasoline. Platinum dioxide (or Adams catalyst) is a catalyst for hydrogenation, especially for the production of vegetable oil. Platinum metal can catalyze the decomposition of hydrogen peroxide into water and oxygen.
2. Standards of weights and measures
During the period from 1889 to 1960, the definition of rice was based on the length of a special platinum-iridium alloy rod (90: 10), which was called international rice source. The original of 1799 is platinum. The original international kilogram device is a cylinder made of the same batch of platinum-iridium alloy of 1879, and it is also the standard weight of kilograms.
The standard hydrogen electrode is made of platinum, which is also because platinum has high corrosion resistance.
3. Precious metals
Platinum is a precious metal trading commodity. The ISO currency code of platinum ingot is "XPT". Platinum coins, platinum bars and platinum ingots can be traded or collected. Because platinum is not easy to corrode and has a shiny appearance, it is also used as jewelry, usually 90% to 95% alloy. Publications on jewelry trading generally advise jewelers to scrape some scratches on the surface of platinum.
In the watchmaking industry, many companies will use platinum to make limited edition watches. Platinum will neither lose its luster nor be scratched (compared with gold), so it is very suitable for clocks and watches.
Like other industrial commodities, the price of platinum fluctuates more than that of gold. In 2008, the price of platinum dropped from $2,252 to $774 per troy ounce, and its market value shrank by nearly two-thirds. Compared with the same period, the price of gold dropped from about $0/000 per ounce to about $700, and the market value only dropped by one third.
In the sustained and steady growth economy, the price of platinum is often twice that of gold; In unstable times, due to the reduction of industrial demand, platinum prices generally fall below the gold price level. When the economy is depressed, the price of gold is more stable because its demand is not driven by industrial use. /kloc-in the 0/8th century, Louis XV of France announced that platinum was the only metal worthy of the king in view of its rarity.
4. Other uses
Platinum wire can be used as an electrode in the laboratory. Thermogravimetric analysis will use platinum plate and support, because it must be strictly chemically inert at high temperature (about1000 C). Platinum is an alloy additive for various metal appliances, such as metal wires, corrosion-resistant experimental containers, medical equipment, dentures, electrical contacts and thermocouples. Platinum-cobalt alloy and iron-platinum alloy can be made into strong permanent magnets. It is also the main material of hard disk recording layer. Platinum-containing anodes are used in ships, pipelines and steel docks.
5, a symbol of dignity
Platinum is extremely rare and is usually regarded as a symbol of nobility. The platinum card service level of credit cards, debit cards and some membership cards is generally higher than that of gold cards. For records, the "White Gold Award" is the second highest honor, lower than diamonds and higher than gold, silver and bronze. For example, in the United States, records that sell more than one million copies will be called "platinum records" and records that sell more than ten million copies will be called "diamond records". Other commodities will also be called "platinum" if the surface is silvery white. Queen Elizabeth's crown was specially made for the coronation of George VI, and its frame was made of platinum. This is the first British crown to use platinum.
Platinum health and safety
According to the Centers for Disease Control and Prevention, short-term exposure to platinum salt will irritate eyes and throat, and long-term exposure may lead to allergic reactions in respiratory tract and skin. The current standard exposure in the United States is 2 micrograms of platinum per cubic meter of air, taking the average value during the 8-hour working period.
Platinum antineoplastic drugs, such as cisplatin, are currently used in chemotherapy and have good effects on some tumors.
Platinum is a catalyst for producing some silicone rubber and gel, which are components of various medical implants, such as breast implants, joint prostheses, artificial lumbar intervertebral discs and so on. After investigation by many institutions, including the US Food and Drug Administration, there is no evidence that platinum is toxic in the body.