(1) visual inspection method: marking: each piece of jewelry should be engraved with the chemical composition seal, such as (pt 900) and (PT 750). All stamps that begin with "PT" are platinum ornaments: platinum is tin white, that is, white with gray and bright luster.
(2) Instrument detection: 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 is extremely dense and feels heavy when weighed by hand. The density measured by hydrostatic pressure method should be 2 1.43g/cm. The melting point of platinum is as high as 178. Acid test when the color is unchanged: platinum is chemically stable and insoluble in ordinary acids. Draw platinum on the touchstone, drop hydrochloric acid, and try with hydrogen peroxide under the condition of unchanged wear marks: take a little platinum powder and put it into the hydrogen peroxide bottle, and hydrogen peroxide will immediately produce bubbles. After the reaction, platinum can still be used without any damage.
■ Seven characteristics of platinum
Platinum has always been regarded as a precious metal because of its unique characteristics. In recent years, the International Platinum Association has strongly advocated it, making it more and more important in the wedding ring.
■ Common identification methods of platinum
1. color Zephyr: pure platinum is white with bright luster, platinum is beige, and silver is white. Can be distinguished from the surface color.
2. Hand balance method: the density of platinum reaches 265,438+0.45. Through the balance 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).
3. Melting method: 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.
4, marking method: platinum jewelry has a standard imprint. Internationally expressed by PT or PT. For example, the purity of PT950 platinum is 950%.
5. Natural gas method: put jewelry on the twisted gas stove mouth 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.
6. Spot measurement method: A Put mercury on platinum, platinum will not be polluted, and gold and silver will be polluted by combining with mercury. 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.
■ Look at the logo platinum.
Platinum jewelry usually expresses the texture of jewelry with a few thousandths of platinum, which is also one of the basis for jewelry pricing. Common labels are as follows:
Foot platinum: the platinum content is not less than 990, and it is marked with "foot platinum" or "Pt990".
950 Platinum: The platinum content is not less than 950, and it is marked with "Platinum 950" or "Pt950".
900 Platinum: The platinum content is not less than 900, and it is marked with "Platinum 900" or "Pt900".
The hardness of pure platinum is small, so in order to increase the hardness, a certain proportion of precious metals such as palladium, rhodium and iridium must be added. Pt950 contains 5% palladium, rhodium and iridium, and its hardness is still relatively low, so it is generally used for plain platinum jewelry. Pt900 contains 10% palladium, rhodium and iridium, and its hardness is just suitable for inlaying ornaments. At present, most platinum ring holders are made of Pt900, but a few manufacturers use Pt950 to make ring holders.
Because metals such as palladium, rhodium and iridium are rarer and more expensive than platinum, the price of Pt900 is correspondingly higher than that of Pt950. However, many consumers have formed a habit of understanding gold in the past: the higher the purity of gold, the more valuable it is, and it is applied to the relationship between the quality and price of platinum. So some merchants take advantage of this, deliberately marking the price of Pt950 higher than Pt900, misleading consumers to buy, so as to obtain income, which is bound to be suspected of fraud.
■ How to distinguish platinum and silver jewelry?
Platinum is the main material for making jewelry because of its exquisite color and the strongest plasticity. It is expensive and rare, never fades and oxidizes, and its performance is stable. Because the colors of silver and platinum are very close, it is easy to be confused from the outside. Here are some ways to distinguish them:
(1) Seal identification: Jewelry products should be marked with seals and their purity according to national standards. If the jewelry has the words "PT" or "PLATNUM" or "PLAT", it is platinum; If the word "S" or "SILVER" is on the jewelry, it is silver.
(2) Weighing: the specific gravity of platinum is 2 1.4, and that of silver is 10.49. Platinum with the same volume weighs twice as much as silver, so it can be distinguished by weighing it by hand.
(3) Comparison of appearance and hardness: When platinum is carefully observed by naked eyes, it will be slightly light gray and bright white, and its texture is hard. It is difficult to scrape the scar with a pin. Its Mohs hardness is 4.3, while silver is white, smooth and delicate, and it will turn gray or black when it is slightly oxidized. Its Mohs hardness is 2.7, which is much softer than platinum.
(4) Combustion method: Platinum can resist high-temperature oxidation with a melting point as high as 1770? 0? 2C, it will not melt when burning with ordinary high temperature (gasoline), and the color will remain unchanged or there are quenching marks after cooling. 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.
(5) Chemical method: Platinum is extremely stable in chemical properties and corrosion-resistant, and will not reflect when it meets any acid or alkali, while silver is not resistant to strong acid corrosion.