Pawn gold jewelry color detection and identification method

In the pawn business, the pawn products of civilian products are the most numerous, and the most complicated and complicated, among which the gold jewellery pawns are mostly. When customers take gold jewelry to pawn, the pawn staff always has some doubts about the gold content in the gold jewelry. Because the price of gold jewelry is high, a slight negligence will cause economic losses to the enterprise. Therefore, it is very important to understand the identification method and identification method of gold jewelry.

Let's talk about the detection of gold jewelry and the matters needing attention in the process of gold jewelry pawn business:

First, it is easier to grasp the six methods for the identification of gold:

1. Identify colors. Look at the color of gold appearance, as the saying goes, gold is "seven green, eight yellow, nine purple, ten red", because it contains different types of impurities and different compositions and different colors. Pure gold shines, and mixed gold has a little bit of trouble. The jewellery containing gold is 70% green, and the gold containing 80% is yellow. The gold-containing glutinous rice is yellow and transparent, and the gold content is 10%.

2, heavier. The specific gravity of gold is 19.3g/cm3, and the relationship between coloration and specific gravity is large. When the specific gravity is close to 19.3, the higher the pure gold. Whether it is commensurate with the size of the hand by the weight of the hand, the shape is large and light may be adulterated. But generally in the hands, if you feel a little sinking, you can feel that it is real gold jewelry, which shows that the gold body is small and heavy. Be wary of stupid and light ornaments, and carefully identify whether it is a fake or a fake.

3, try hard and hard. The higher the color of gold jewelry, the softer it is, the less elastic it is. The gold is bitten or needled with a light mark, and the hand is folded without broken lines. The low color steel is hard; the heavy blender is elastic, brittle and fragile. Pure gold is soft, generally not used for inlaid jewelry, so the inlaid gold ornaments claim to be 24K, there must be fraud.

4, knocking. Two identical gold ornaments collide, the high color is the voice of the people, the low color is the voice, and the gold is the sound.

5. Reagent method. That is, try 45% nitric acid: gold, platinum, no change, silver, black, copper, green foam. This is because gold is chemically stable and will not be oxidized under any conditions, and is also very stable in water, air, hydrogen sulfide or salt, and alkali environments. Gold is hardly soluble in any single acid, only soluble in aqua regia (a mixture of hydrochloric acid and nitric acid in a ratio of 3 to 1).

6. Check the stamping method. Gold jewelry produced by regular manufacturers is covered with gold and manufacturer's mark, such as cover 24K, 22K, 18K and so on.

Second, the static water density test method:

The determination of the density value of gold jewellery by hydrostatic density is a quick and accurate method for identifying gold jewellery, and it is not harmful to gold jewellery, so that it can better protect pawn items and is worth promoting.

To measure the hydrostatic density of gold jewellery, a specific gravity balance must be used:

1. First adjust the balance so that the balance is at zero.

2. Put the gold jewelry on the scale of the balance and first weigh the weight of the gold jewelry in the air (P).

3. Put the gold jewelry into the water scale and weigh the weight of the gold jewelry in the water (P1).

4. Substituting these two values ​​into the specific gravity formula: G=P/(P-P1)×the specific gravity of the liquid (the density of pure water is 1g/cm3, so it can be ignored).

5. The calculation result is the specific gravity value G of the gold jewelry. After the specific gravity value, the density unit g/cm3 is added, which is the density value of the jewelry. If the measured result is Au<19.21g/cm3 or pt<21.25g/cm3, the gold jewelry measured is not pure gold (24K) jewelry.

Third, the static water density detection method should pay attention to the following matters:

1. This method is applicable to the inspection of pure gold jewelry.

2. For K gold jewelry, because the metals added by various manufacturers in K gold jewelry are different: copper, silver, palladium, nickel, zinc, etc., the density in K gold is different, there is no uniform standard, do not understand K In the case of a gold jewelry formula, it cannot be extrapolated. The results tested can only be used as a reference.

3, the static water density test can only detect solid gold jewelry, hollow gold jewelry and insert gold jewelry can not be accurately detected, the error is very large.

4. The method is also applicable to the detection of platinum jewelry. The density of pure platinum is 21.45 g/cm3.

5, gold jewelry generally gold is expressed in 24K, each 1K indicates that the gold content is 4.166%.

6. When the gold content of the tested gold jewelry is less than 75%, it is best not to give the pawn because the other metal elements it contains are too complicated.

When testing platinum jewellery, it should be noted that the illicit molecules use palladium Pd (density of 12.16g/cm3) and sheet metal Lr (density of 22.40g/cm3) to deceive. After the static water density detection method, it is best to use nitric acid drops. Chemical testing was carried out, and true platinum was not present in the presence of a chemical reaction. When the platinum content is less than 80%, it is best not to give pawn.

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