5 thoughts on “How to identify the purity of gold”
Kate
1. Look at the marks: now the gold jewelry produced by Chinese manufacturers is purified and prepared according to international standards, and marked with K to indicate the amount of gold in the metal products. According to the words of 24K or 18K on the mark, we can know the quality of the jewelry. However, according to the regulations, if it is lower than 10k, we cannot print the number of K gold
2. Color: the higher the purity of gold jewelry, the darker the color. As people often say, "seven green, eight yellow, nine purple and ten red", that is, if the gold jewelry is blue yellow, the gold content can reach 70%; It is yellow and contains 80-90% gold; If it is reddish yellow, the gold content can reach more than 95. Of course, it is not enough to distinguish the fineness and authenticity of gold jewelry only by color
3. Weight: the specific gravity of gold is 19.3, higher than that of other metals. The weight of gold with the same volume is 1.8 times that of silver and 2.2 times that of copper. Therefore, the real gold should feel heavy in the hand, while the fake gold should feel lighter
4. Listen to the sound: throw the gold ornaments on the table or on the hard ground. The lower the gold content, the greater the elasticity, the higher the jump, and the clear sound will be made, and there will be aftersounds; The higher the gold content, the smaller the elasticity, the lower the jump, the lower the sound, and no aftersound
5. Hardness test: the higher the gold content of jewelry, the softer it is. It is easy to bend by hand, with good toughness and not easy to break. If it is scratched with a hard object, it will leave a clear scratch; The lower the gold content is, the harder it is. It needs more strength to bend and it is easy to break. When it is carved with hard things, the scratch is not obvious
6. Scientific detection: first, identification by fire. Put the jewelry on a smokeless fire, and the color of pure gold will not change after burning; The color darkened or blackened is fake gold or lack of fineness. The second is chemical method. Spot test with sulfuric acid with a concentration of 45% or 70%, and the gold remains unchanged; Silver turns black; The copper is bubbling green. Because silver, copper and other metals are dissolved in acids, chemical reactions will occur
According to the principles and properties of analysis and testing methods, these methods can be roughly divided into density method, X-ray method, fire assay method, gravimetric method, inductively coupled plasma atomic emission spectrometry, etc
1 density method
the principle of density method is to determine the mass of a sample in the air according to Archimedes principle and divide its volume to obtain the density of the sample to be measured, and then calculate the purity of gold in jewelry according to the density of possible impurity elements in jewelry and the density of gold. This is the principle of traditional density method, At present, the latest water specific gravity gold meter (gold k-number meter) combines the Archimedean principle with the current microelectronic technology. It uses German imported sensors to directly convert the purity of precious metals through the detection of the density of precious metals. It can directly read the K value of gold, Pt value of platinum, density value, purity percentage, etc. at present, it has been widely used in jewelry silver houses, pawn companies, precious metal recycling and processing, and raw material detection of jewelry factories
2. X-ray fluorescence spectrometry
X-ray fluorescence spectrometry is a simple and rapid method to determine the purity of gold jewelry. The principle is that the X-ray tube (or radiation source) generates incident X-rays (primary x-rays) to excite the measured sample, the elements in the excited sample will emit secondary X-rays, and the secondary x-rays emitted by different elements have specific energy characteristics or wavelength characteristics; The detection system measures the energy and quantity of these emitted secondary X-rays, and uses software to directly convert them into the types and contents of various elements
The simplest identification method is to use the principle of buoyancy law, namely Archimedes law. The steps are as follows: 1. Specific operation method 1. First weigh the gold and silver jewelry on a high-precision electronic scale (accuracy: 0.01g) and record its weight 2. Cut 1 / 2 of the plastic bottle filled with purified water to leave half of it, then pour a proper amount of purified water, put it on the electronic scale to weigh and record its weight; The plastic bottle containing purified water continues to be placed on the electronic scale 3. Tie the gold and silver jewelry to be identified with a thin wire (the thinner the better). Dip the jewelry into the plastic bottle with pure water on the electronic scale with one end of the thin wire. Be careful not to sink the jewelry, nor expose the jewelry to the water, nor touch the inner wall of the plastic bottle. At this time, record the displayed weight II. Calculation according to the above operation method, three groups of data are obtained: the first group is the weight of the jewelry, the second group is the weight of the plastic bottle containing purified water, and the third group is the weight of the plastic bottle after sinking into the jewelry hypothesis 1: we need to identify silver jewelry. The weight of the jewelry is 105g, the weight of the plastic bottle containing purified water is 200g, and the weight of the plastic bottle immersed in jewelry is 210g 210g-200g = 10g (the added weight of the plastic bottle after being immersed in jewelry). According to Archimedes' Law: "an object immersed in a static liquid is subject to a buoyant force, and its volume is equal to the weight of the fluid displaced by the object", the added weight of the plastic bottle after being immersed in jewelry is the volume of jewelry, which is 10cm, that is, the weight of 10G pure water (the density of pure water is 1g / 1cm)
we know that the density of pure silver 9999 is 10.5 g / cubic centimeter, the weight of silver jewelry is 105 g, and the volume is 10 cubic centimeter, that is, 10 cubic centimeter × 10.5 g / cubic centimeter = 105 g, which can be determined to be pure silver hypothesis 2: what we need to identify is gold jewelry. The weight of the jewelry is 19.3 g, the weight of the plastic bottle containing purified water is 200 g, and the weight of the plastic bottle after immersion in the jewelry is 201 G 201g-200g = 1g (the added weight of the plastic bottle after immersion in jewelry). The added weight of the plastic bottle after immersion in jewelry is the volume of jewelry, i.e. 1 cubic centimeter, i.e. the weight of 1 gram of purified water
we know that the density of pure gold 9999 is 19.3 g / cubic centimeter, the weight of gold jewelry is 19.3 g, and the volume is 1 cubic centimeter, that is, 1 cubic centimeter x 19.3 g / cubic centimeter = 19.3 g, which can be determined to be pure gold according to the above operation and calculation, if the density of jewelry calculated by reverse calculation does not conform to the inherent density of the metal, it is either not pure enough or it is fake jewelry at all.
1. Look at the marks: now the gold jewelry produced by Chinese manufacturers is purified and prepared according to international standards, and marked with K to indicate the amount of gold in the metal products. According to the words of 24K or 18K on the mark, we can know the quality of the jewelry. However, according to the regulations, if it is lower than 10k, we cannot print the number of K gold
2. Color: the higher the purity of gold jewelry, the darker the color. As people often say, "seven green, eight yellow, nine purple and ten red", that is, if the gold jewelry is blue yellow, the gold content can reach 70%; It is yellow and contains 80-90% gold; If it is reddish yellow, the gold content can reach more than 95. Of course, it is not enough to distinguish the fineness and authenticity of gold jewelry only by color
3. Weight: the specific gravity of gold is 19.3, higher than that of other metals. The weight of gold with the same volume is 1.8 times that of silver and 2.2 times that of copper. Therefore, the real gold should feel heavy in the hand, while the fake gold should feel lighter
4. Listen to the sound: throw the gold ornaments on the table or on the hard ground. The lower the gold content, the greater the elasticity, the higher the jump, and the clear sound will be made, and there will be aftersounds; The higher the gold content, the smaller the elasticity, the lower the jump, the lower the sound, and no aftersound
5. Hardness test: the higher the gold content of jewelry, the softer it is. It is easy to bend by hand, with good toughness and not easy to break. If it is scratched with a hard object, it will leave a clear scratch; The lower the gold content is, the harder it is. It needs more strength to bend and it is easy to break. When it is carved with hard things, the scratch is not obvious
6. Scientific detection: first, identification by fire. Put the jewelry on a smokeless fire, and the color of pure gold will not change after burning; The color darkened or blackened is fake gold or lack of fineness. The second is chemical method. Spot test with sulfuric acid with a concentration of 45% or 70%, and the gold remains unchanged; Silver turns black; The copper is bubbling green. Because silver, copper and other metals are dissolved in acids, chemical reactions will occur
reference source: Baidu Encyclopedia - gold purity
According to the principles and properties of analysis and testing methods, these methods can be roughly divided into density method, X-ray method, fire assay method, gravimetric method, inductively coupled plasma atomic emission spectrometry, etc
1 density method
the principle of density method is to determine the mass of a sample in the air according to Archimedes principle and divide its volume to obtain the density of the sample to be measured, and then calculate the purity of gold in jewelry according to the density of possible impurity elements in jewelry and the density of gold. This is the principle of traditional density method, At present, the latest water specific gravity gold meter (gold k-number meter) combines the Archimedean principle with the current microelectronic technology. It uses German imported sensors to directly convert the purity of precious metals through the detection of the density of precious metals. It can directly read the K value of gold, Pt value of platinum, density value, purity percentage, etc. at present, it has been widely used in jewelry silver houses, pawn companies, precious metal recycling and processing, and raw material detection of jewelry factories
2. X-ray fluorescence spectrometry
X-ray fluorescence spectrometry is a simple and rapid method to determine the purity of gold jewelry. The principle is that the X-ray tube (or radiation source) generates incident X-rays (primary x-rays) to excite the measured sample, the elements in the excited sample will emit secondary X-rays, and the secondary x-rays emitted by different elements have specific energy characteristics or wavelength characteristics; The detection system measures the energy and quantity of these emitted secondary X-rays, and uses software to directly convert them into the types and contents of various elements
The simplest identification method is to use the principle of buoyancy law, namely Archimedes law. The steps are as follows:
1. Specific operation method
1. First weigh the gold and silver jewelry on a high-precision electronic scale (accuracy: 0.01g) and record its weight
2. Cut 1 / 2 of the plastic bottle filled with purified water to leave half of it, then pour a proper amount of purified water, put it on the electronic scale to weigh and record its weight; The plastic bottle containing purified water continues to be placed on the electronic scale
3. Tie the gold and silver jewelry to be identified with a thin wire (the thinner the better). Dip the jewelry into the plastic bottle with pure water on the electronic scale with one end of the thin wire. Be careful not to sink the jewelry, nor expose the jewelry to the water, nor touch the inner wall of the plastic bottle. At this time, record the displayed weight
II. Calculation
according to the above operation method, three groups of data are obtained: the first group is the weight of the jewelry, the second group is the weight of the plastic bottle containing purified water, and the third group is the weight of the plastic bottle after sinking into the jewelry
hypothesis 1: we need to identify silver jewelry. The weight of the jewelry is 105g, the weight of the plastic bottle containing purified water is 200g, and the weight of the plastic bottle immersed in jewelry is 210g
210g-200g = 10g (the added weight of the plastic bottle after being immersed in jewelry). According to Archimedes' Law: "an object immersed in a static liquid is subject to a buoyant force, and its volume is equal to the weight of the fluid displaced by the object", the added weight of the plastic bottle after being immersed in jewelry is the volume of jewelry, which is 10cm, that is, the weight of 10G pure water (the density of pure water is 1g / 1cm)
we know that the density of pure silver 9999 is 10.5 g / cubic centimeter, the weight of silver jewelry is 105 g, and the volume is 10 cubic centimeter, that is, 10 cubic centimeter × 10.5 g / cubic centimeter = 105 g, which can be determined to be pure silver
hypothesis 2: what we need to identify is gold jewelry. The weight of the jewelry is 19.3 g, the weight of the plastic bottle containing purified water is 200 g, and the weight of the plastic bottle after immersion in the jewelry is 201 G
201g-200g = 1g (the added weight of the plastic bottle after immersion in jewelry). The added weight of the plastic bottle after immersion in jewelry is the volume of jewelry, i.e. 1 cubic centimeter, i.e. the weight of 1 gram of purified water
we know that the density of pure gold 9999 is 19.3 g / cubic centimeter, the weight of gold jewelry is 19.3 g, and the volume is 1 cubic centimeter, that is, 1 cubic centimeter x 19.3 g / cubic centimeter = 19.3 g, which can be determined to be pure gold
according to the above operation and calculation, if the density of jewelry calculated by reverse calculation does not conform to the inherent density of the metal, it is either not pure enough or it is fake jewelry at all.
One way is to look at the color: the higher the purity of gold jewelry, the darker the color.