Sihaiwang: platinum is a kind of precious metal commonly used in jewelry. Its characteristics are also rare and rare. It will never fade or wear. No matter investment or jewelry, platinum is a good choice, so how to identify the authenticity of platinum? What are the methods of platinum identification? Let's take a look at it!
Identification of platinum
The simplest and most principled formula to buy platinum:
1. Just like the gold with 9999, only the gold with pt950 can be regarded as platinum!
2. All marks 750, no matter what the preceding symbols are, are 18K (18 divided by 24 equals 75%)!
3. There is no platinum in 18K platinum!
If you buy real platinum, the pt950 mark must be placed in the column of identification certificate bracket, just like 9999 gold. Because only pt950 has international standards, that is to say, it can be put all over the world. Jewelers are not brave to make mistakes. From the perspective of consumption ability, you can buy any kind of jewelry. But there are two points to consider: first, after-sales service of non-standard color bracket may encounter difficulties, and it is difficult to find a matching color; second, from the perspective of maintenance, the standard color is easy to cash. In fact, the real 18K is not cheap. The key is to find out the ingredients. What is the real 18K gold? Due to the rare output, high price and high melting point of platinum, platinum is rarely used to produce real K platinum in general countries. After the outbreak of World War II, due to the important military use of platinum, the U.S. government once banned the non military use of platinum, replacing platinum with white K-gold (alloy of gold and other white metals), although white K-gold can never replace platinum from many aspects such as luster, hardness, etc. At present, in order to meet the needs of consumers for platinum, gold and palladium or nickel, silver, copper, zinc and other metals are used to smelt into a white alloy, known as' K platinum '. The quality of k-platinum is the same as that of K-gold. The bundle quality is 24. The quantity of gold in the bundle is k-number of k-platinum.
Color and lustre
Platinum is silver white or gray white, which is between the color of silver and nickel. Silver luster is white, easy to be oxidized with black spots or black; the texture is fine and smooth.
proportion
The ratio of platinum to gold is 15-19 or 21.4. The proportion of silver is 10.49. Weigh the same size of platinum and silver jewelry by hand and you will find the difference between them.
Destroy by fire
The color of pure platinum remains the same after heating or fire cooling. After the silver is burnt, its surface will present the moist red or the black red tone.
Bending
Pure platinum is easy to bend and break straight reduction; low color, hard and brittle, hard to bend.
Listening
When striking, if the sound of "toto" is emitted without rhyme, it is pure platinum; if the sound of "jingling" is emitted, it is low platinum.
Mercury test
Using the property that platinum does not absorb mercury, apply mercury on the grinding path of the touchstone. If mercury is absorbed, it is made of gold, silver and platinum.
Nitrate test
Grind the platinum ornaments to be identified on the touchstone, and cover the grinding path with a layer of salt, which is unnecessary to be covered tightly; then, drop nitric acid on the salt until it is wet; add some hot paper soot on the salt to play a catalytic role. After 20 minutes, rinse salt and nitric acid with water. After work, look at the side. If there is no change, the color will be about 99%; if there is slight acid mark, the color will be about 95%; if there is a large trace of nitric acid, the color will be about 80-90%; if the grinding path is corroded, the trace will be gray, the color will be about 70%; if all the traces disappear, it will be fake platinum.
Identification of spontaneous combustion of gas lamp
Put the platinum jewelry to be identified on the gas lamp port. If it is true platinum, after a minute or two, the ornaments will turn red and the gas lamp will automatically light up. If the ornament is not platinum, there is no such reaction.
Hydrogen peroxide reaction method
Platinum is a good catalyst with unique catalytic effect. With this property, platinum can be identified quickly. Hydrogen peroxide reaction is commonly used. The specific method is: take a little powder of the substance to be tested and place it in a plastic bottle filled with hydrogen peroxide (H2O2). If it is platinum, the hydrogen peroxide will immediately foam in a white wave and decompose a large amount of oxygen. The platinum after reaction is still intact and can be recovered (it only accelerates the decomposition); if it is fake platinum or other white metals, such as lead, silver, aluminum, etc., there is no such reaction.
Other
The geological department can also be invited to do electron probe testing.
Similar distinction
Platinum is characterized by silver white color and streak, hardness of 4-4.5, specific gravity of 15-19 or 21.4, stable chemical properties, insoluble in ordinary acids, and easy to distinguish from similar metals.
The difference between platinum and silver
Platinum and silver ornaments are very popular in the market, and have always been the favorite ornaments of many women. Because platinum and silver have many similarities, it is necessary to distinguish them.
Platinum and silver are different in hardness, specific gravity and chemical stability. Generally, the following simple methods are used to distinguish.
(1) comparison of color and hardness
Platinum is silvery white or grayish white; its texture is hard, and its Mohs hardness is 4-4.5. The color of silver is pure white; the texture is smooth and delicate, the Mohs hardness is 2.5-2.7, which is softer than platinum, and can leave traces by scratching with fingernails; the foil is inelastic, easy to bend with hands, and difficult to recover.
(2) specific gravity test
The density of platinum is high and the ratio is significant. Although silver is silvery white, its relative density is 10.53g/cm3, specific gravity is 10-11, only 1 / 2 of platinum. Silver of the same volume is half lighter than platinum. Generally, platinum and silver can be roughly distinguished by weighing them by hand.
(3) chemical method
Silver is unstable in chemical properties, soluble in nitric acid, and emits nitrogen dioxide gas. Platinum is insoluble in nitric acid, so it can dissolve quickly in heated aqua regia. At normal temperature, its dissolution rate is very slow, which is difficult to detect by naked eyes. Put the platinum chip on the touchstone and drop a little mixture of nitric acid and hydrochloric acid. If the debris is still present, it is platinum; if the debris dissolves and disappears, it is silver.
Distinction with metal lead and aluminum
Platinum, lead and aluminum are distinguished by different deformation characteristics and specific gravity. Metal lead and aluminum are inelastic and cannot be recovered after deformation; moreover, their specific gravity is much smaller than that of platinum. The specific gravity of lead is 11.36 and that of aluminum is 2.7, which are about 1 / 2 and 1 / 8 of platinum respectively. It can be distinguished only by weighing by hand.