Method for detecting the purity of gold precious metals(Part 2)

Density method

The advantages of the digital display water specific gravity gold measuring instrument are: no calculation, no need to make additional jigs such as hanging wires, fast analysis speed, no damage to the sample, and the machine has a temperature compensation function, which can avoid the deviation of the result due to different water temperatures. And the measurement cost is low, and it can be used as a general balance. It can quickly distinguish between gold-coated and gold-plated with copper, silver, nickel, cadmium, tin, lead and other metals as the carcass. For samples that are generally gold-plated gold-plated or too low in purity, the instrument will display the LO automatic alarm prompt.

The principle of density method is to measure the mass of the sample in the air according to the principle of Archimedes divided by its volume to obtain the density of the measured sample, and then calculate the purity of the gold in the jewelry based on the density of the impurity elements in the jewelry and the density of the gold. This is the principle of the traditional density method. At present, the latest water specific gravity gold meter (gold K-number analyzer) combines the Archimedes principle with the current microelectronics technology. It uses a German imported sensor and directly converts it through the detection of precious metal density. Precious metal purity can directly read gold K value, platinum PT value, density value, purity percentage, etc. It has been widely used in jewelry silver buildings, pawn companies, precious metal recycling and processing, jewelry factory raw material testing and other fields.

The specific test methods are as follows:

Test the weight (quality) of the sample in the dry state, press the OK key to remember.

Weight (volume) of the test sample in water, press the OK key, the instrument automatically displays the sample K value or PT value, purity%.

Some limitations of the density method: For a completely hollow sample, water cannot penetrate into the sample and the instrument cannot read the true volume of the sample, which can easily lead to deviations in the test results. For non-uniform samples, such as diamond rings, gold inlaid jade, pendant with rope and jewelry cannot be tested directly, it needs to be split to get accurate test results. For metals with a density close to that of gold and platinum, such as iridium, tungsten and other metals, gold-plated gold plating cannot be distinguished by the density method.

Some details and skills that need to be paid attention to when testing the density method: When the sample is placed in water, make sure that the surface of the sample is free of bubbles. Jewelry samples with complex structures, such as transfer beads, semi-hollow bracelets or necklaces, when placed directly in the water, due to Burrs or cracks are very likely to form surface or internal bubbles. When testing such samples, after testing the quality of the dry state, soak and wash with 95% medical alcohol and then put it in water. The reason is that alcohol is extremely permeable and easily enters the inside of the sample hollow. Alcohol can eliminate the tension of the water surface. The sample surface or hollow part is covered with alcohol and placed in water. Since the density of alcohol is lower than that of water, it will float out of the water surface. At the same time as the alcohol evaporates, water will occupy the hollow part of the sample into which the original alcohol enters. This will ensure that no bubbles will form on the surface and the hollow part of the sample. The test results will be more accurate and reliable.





Post time: Jul-10-2020

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