Identify adulteration:
1. Does gold have white highlights?
Cut the gold bars or jewelry with scissors, and observe the section with a magnifying glass. If you see white bright spots, because gold and iridium can't blend together, it means that gold is doped with iridium.
2. Specific gravity measurement:
First, measure the weight of a pure gold bar with a balance, then put the gold bar into a measuring cup and pour water to drown it. Then put the detected gold bars into a measuring cup and observe whether the scale of water rises or falls. As long as there is a change, it means that gold bars are not pure gold. But if it is gold jewelry, this method is not applicable, because there is air in gold jewelry.
3. Real gold is not afraid of fire;
Put gold bars or gold jewelry on the fire for a period of time and observe its changes. Because iridium will combine with oxygen in the air to produce oxidation reaction, gold bars with insufficient purity will turn gray; And pure gold will appear bright red after being baked by fire. However, this method may have some damage to jewelry.
Extended data:
1, physical properties of gold
(1) color:
The steam released when gold melts is green; Its gold powder is usually brown when it is melted; If it is cast into thin slices, it can transmit green light.
(2) Extensibility:
Extremely powerful. 1 oz gold can be stretched to 50 miles long, and its ductility makes it easy to cast, making it a good choice for making jewelry. Of all metals, gold has the greatest pulling force.
(3) ductility:
Second to none. It will cause extremely thin gold sheets to roll up easily. Gold weighing 1 ounce can be hammered into 1 foot thickness and 100 square foot thickness. The ancients hammered it into thin slices and spread it in temples and palaces for decoration. All these can show that gold is extremely flexible and plastic.
2. Four textures of gold
(1) The meanings of red gold and pure gold are similar, but the standard of red gold varies with time and place. Gold with a purity of 99.6% sold in the international market is called red gold. Domestic red gold is generally between 99.2% and 99.6%.
(2) Non-ferrous gold, also known as "secondary gold" and "tidal gold", refers to gold with low fineness. Due to the different contents of other metals, the purity of these gold is as high as 99% and as low as 30%.
According to the classification of other metals, ripe gold can be divided into solid gold, mixed gold and K gold. Clear gold means that gold is only mixed with silver, regardless of its fineness. Clear gold is more common in gold bars, ingots, nuggets and various utensils and gold ornaments.
(3) Mixed color gold means that gold contains other metals such as copper, zinc, lead and iron besides silver. According to the different types and quantities of metals, it can be divided into small mixed gold, large mixed gold, bronze mixed gold and lead mixed gold.
(4)k gold refers to gold made of silver and copper in a certain proportion according to the formula that pure gold is 24k. Generally speaking, the more silver in K gold, the bluer the color; If the proportion of copper is large, the color is purple.
Baidu encyclopedia-gold