There are several ways to identify gold, but it is better to go to a professional institution for testing for insurance purposes.
1. Classification of gold identification methods
Gold identification methods are divided into two categories: destructive identification methods and non-destructive identification methods. For example, treating gold with mineral acids such as aqua regia to prepare a gold-containing chemical solution for chemical analysis; this method is a destructive identification method. For another example, electrify the upper and lower pellet-shaped gold spectrum electrodes to generate an arc and record the spectrum signal; this method is a non-destructive identification method.
These two identification methods occupy a certain position in the identification of finished gold products. However, the detrimental identification method does not apply to the identification of gold jewelry.
In addition, general consumers can use simple identification methods.
2. Non-destructive identification method
non-destructive identification methods mainly include: touchstone method, microanalysis method, specific gravity method (density method) and X-ray fluorescence spectrometry.
2.1. Touchstone method
The touchstone method is to compare the color of the streaks carved out on the touchstone of gold with the color of the gold standard series to determine the color of gold jewelry. This method is simple and easy to implement and does not require equipment. therefore. It has been adopted for a period of time. However, the human error is large, the accuracy is not high, and the gold jewelry is slightly damaged, and a very expensive gold standard series is required.
Micro-area analysis methods mainly include: electron probe, laser micro-area spectroscopy and scanning electron microscopy energy spectroscopy. This method uses a beam of electrons or laser light to illuminate a tiny area on the gold. According to the spectrum or energy spectrum generated in this tiny area, the color of gold and the content of impurity elements are calculated. This method is particularly suitable for the detection of fineness (grade) of tiny gold particles in gold ore. For gold products and jewelry, because the sampling area is too small, the representativeness is poor, and the sensitivity and accuracy are not ideal.
2.3. Specific gravity method
The ancient methods of gold identification are empirical identification method and sampling identification method. The former has poor reliability; the latter affects the appearance of gold jewelry. The specific gravity measurement method is abbreviated as the specific gravity method, which is a new method of gold identification. It can determine the authenticity of gold jewelry and determine its gold content within a few minutes. Therefore, it is a fast identification method for gold jewelry.
The specific gravity method uses an analytical balance (modified diamond balance) as a testing instrument. According to the weight of gold in the air and aqueous solution, according to Archimedes’s law, the proportion and fineness of gold are calculated. If the weight of the gold jewelry in the air is M and the weight in the carbon tetrachloride CCl4 solution is N, the formula for calculating the gold content Q is:
Q = [M / (M+N)] ×1.58
In the formula, 1.58-the density coefficient of carbon tetrachloride CCl4 solution.
If other solutions are used for measuring heavy liquid, the density coefficient in the above formula should be changed accordingly. For the measurement results, the error correction should also be carried out according to the weight and fineness of the gold jewelry, so as to calculate the gold content of the gold jewelry. This method requires high sensitivity and precision for analytical balances. The choice of measuring heavy liquid is also very important.
The specific gravity method has a high identification accuracy, and ideally, the error can reach within 0.3% to 0.5% (that is, a jewelry is 99.8%, and its measurable range is 99.4% to 99.9%). In addition, the equipment is simple, low in price, and easy to promote. This is a simple, fast and accurate gold measurement method. However, this method is not suitable for the identification of gold-plated, gold-clad and gold-plated jewelry. When gold contains multiple impurity elements or internal defects such as tiny pores, the specific gravity method will make mistakes. At the same time, in the detection process of the specific gravity method, the influence of surface tension is difficult to completely eliminate, which limits the improvement of its accuracy. Therefore, the specific gravity method can only identify the approximate content of gold jewelry.
2.4. X-ray fluorescence spectrometry
X-ray fluorescence spectroscopy is a high-tech method for non-destructive gold identification that has been successfully studied in recent years. It uses a computer-controlled, large-scale precision X-ray fluorescence spectrometer as an identification device. A large area of gold is irradiated by a beam of X-rays. According to the recorded fluorescence X-ray spectrum and intensity, the computer can identify the authenticity and calculate the gold content and the content of impurity elements in the gold product or jewelry. This method does not require any chemical reagents, has no pollution, no damage, and no residual radioactivity. It not only overcomes the defects of the above-mentioned various methods, but also has high accuracy and sensitivity. It is currently a relatively advanced new technology for non-destructive gold identification. The People’s Bank of China has designated X-ray fluorescence spectrometry in Beijing and Tianjin as a gold jewelry identification technology to replace other identification methods.
Post time: Jun-30-2021