Post updated: May 26, 2020
There is no such person who has not seen yellow metal in his entire life. There are several minerals found in nature that are similar in appearance to the yellow metal. But as they say: “all that glitters is not gold.” In order not to confuse the precious metal with other materials, you need to know the density of gold.
Density of noble metal
Molecular structure of gold.
One of the important characteristics of a precious metal is its density. The density of gold is measured in kg m3.
Specific gravity is a very significant characteristic for gold. This is usually not taken into account, since jewelry: rings, earrings, pendants have very little weight. But if you hold a kilogram ingot of real yellow metal in your hands, you can see that it is very heavy. The significant density of gold makes it easier to mine. Thus, washing at sluices ensures a high level of gold recovery from washed rocks.
The density of gold is 19.3 grams per cubic centimeter.
This means that if you take a certain volume of precious metal, it will weigh almost 20 times more than the same volume of plain water. A two-liter plastic bottle of golden sand weighs about 32 kg. From 500 grams of precious metal you can lay out a cube with a side of 18.85 mm.
Table of density of gold of various samples and colors.
The density of the original gold is several units lower than that of the already purified metal and can vary from 18 to 18.5 grams per cubic centimeter.
583 gold is less dense, as this alloy consists of different metals.
At home, you can determine the density of gold yourself. To do this, you need to weigh the precious metal product on ordinary scales, in which the division value must be at least 1 gram. After this, a container with a volume marking must be filled with liquid, in this case water, into which the decoration should be lowered. Care must be taken to ensure that the liquid does not overflow.
After this, we measure how much the volume of liquid has changed after lowering the gold item into the container. Using a special formula, known from school, we calculate density: mass divided by volume.
It must be remembered that a precious metal product is not made of pure gold, so it is necessary to make an adjustment for the density of the alloy sample.
Chemical composition
This metal is an alloy of iron and carbon that contains small amounts of impurities. The percentage of iron reaches levels of more than 90%. Silicon, phosphorus, manganese and sulfur are also present. Carbon - no less than 2.14%. It defines the properties of the entire connection.
The role of carbon
First of all, carbon gives hardness. It is carbon that forms the strength characteristics of the alloy, which is an excellent material for foundry production. But it also reduces ductility and malleability.
Therefore, a hard but brittle metal has a limited range of applications. These are mainly metallurgy, mechanical engineering, automotive manufacturing, production of heavy special equipment, utilities and industrial design.
In cast iron, carbon is present in different forms: as cementite (Fe 3 C), or graphite (lamellar, spherical, flake). Graphite largely determines the properties of this material, which is currently divided into the following types:
How to distinguish real yellow metal from a fake
At the moment, there is a very large percentage of counterfeit gold on both the Russian and foreign markets. There is a huge risk of purchasing gold jewelry containing up to 5% of the precious metal or without it at all. Basic rules when buying gold will help you avoid feeling deceived.
First, you should take a good look at the product. There must be a sample on it. Moreover, it should not consist of crooked numbers or blurry marks. Otherwise, this is the first sign of a counterfeit.
A sample of a unified state hallmark for gold products.
The next sign of a fake is the reverse side of the precious metal jewelry. It must be as well made as the front side, otherwise it is a low-quality product. It is also possible to determine the quality of a product using a characteristic such as gold density, but it is impossible to conduct such an experiment in a store.
There is also a way to determine it, called a strength test. True, it is not always possible to scratch a gold item in front of the seller, so this method cannot be implemented.
Iodine test.
The following chemical methods can serve as good ways to determine the quality of a product. You can drop a little iodine on the yellow metal jewelry. If the speck is dark in color, then we can speak with confidence about the quality of the product being offered. Table vinegar can also help. If, after three minutes spent in it, the precious metal has darkened, then you can safely take the product to a landfill.
Gold chloride can be a great help in determining quality. From the chemistry course, it became known not only the density of gold, but also the fact that it cannot enter into any chemical reactions. Therefore, if after applying gold chloride to a precious metal it begins to deteriorate, then this is a real fake and should belong in the trash.
One of the best ways to protect yourself from purchasing counterfeit goods is to purchase precious metal products in well-known specialized stores.
In this case, there is a high probability of purchasing a truly high-quality product. Even though their price is a little higher than in various shops and markets, the quality is worth it. Otherwise, you can purchase a counterfeit product and very much regret the money saved.
Types of cast iron
Depending on the state of carbon in cast iron, there are:
- The most common is gray cast iron. It has high strength, low shrinkage, low crystallization temperature, and is easy to process. It produces high-quality housings and parts for mechanical engineering (pistons, cylinders, boiler bodies and shut-off valves). Cast iron parts that work with shock-free loads have also proven themselves well: machine tool beds, various shafts and pulleys. Carbon content - from 2.4 to 3.8%. Marking - MF.
- High-strength cast iron (DC) is produced using special heat treatment and the addition of additives (alloying). The graphite in it has a spherical shape and, when melted, combines with the elements of the iron crystal lattice. This improves mechanical properties, which makes it possible to produce reliable crankshafts, cylinder covers, cast pipes and heating devices. According to its characteristics, this type is close to some grades of steel.
- Malleable cast iron is used for the manufacture of artistic products, metal decoration, but mainly for the production of manifolds and the production of parts for agricultural machinery and cars that have to work in difficult conditions. Along with others, it is used in the electrical industry. This alloy is a variety of white.
- White cast iron. So named because of the characteristic white color at the fracture sites. Contains about three percent carbon in the form of carbide and cementite. It is fragile and brittle, therefore it is used in the manufacture of parts that are not subject to special loads.
- The transitional stage between MF (gray) and BC (white) is half cast iron. It contains graphite and carbide in equal proportions, with a total carbon content of 3.5-4.15%. The material is used in the production of parts operating under friction conditions.
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Gemini of gold
There are several metals found in nature that have the same density as gold. These are uranium, which is radioactive, and tungsten. It is cheaper than the yellow metal, but the density of tungsten and gold is almost the same, the difference is three tenths. What distinguishes tungsten from gold is that it has a different color and is much harder than the yellow metal. Pure gold is very soft and can be easily scratched with a fingernail.
A fake gold bar filled with tungsten on the inside.
The fact that the density of elements such as tungsten and gold is the same is very attractive to counterfeiters. They replace gold bars with tungsten of similar density and weight, and cover the top with a thin layer of precious metal. At the same time, the high cost of the yellow metal makes tungsten more popular among young people. Tungsten products are much cheaper and more scratch resistant.
Material extraction
The noble metal is rarely found in nature in its pure form. Typically, platinum contains palladium, iridium, iron and nickel. Sometimes copper, rhodium or osmium are used as impurities. Most specimens are polyxenes (ferruginous variety). No less common are intermetallic compounds: isoferroplatinum and tetraferroplatinum.
The noble mineral can be considered one of the rarest: the earth’s crust contains only 5·10−7% by mass. Known world reserves of the metal are approximately 80 thousand tons. They can mainly be found between South Africa, Russia and the USA. In our country, the main deposits of the material are located in the Krasnoyarsk Territory, the Murmansk and Sverdlovsk Regions, as well as the Khabarovsk and Kamchatka Territories. The largest nugget found in Russia is the “Ural Giant”. The mass of the material discovered at the Isovsky mine is 7860 g.
Minerals are more often found in typical igneous deposits, which are genetically related to ultramafic igneous rocks. Alloys lacking palladium are found among dunites. They are paragenetically related to chrome spinels. The palladite and nickel-palladite varieties can be found in basic igneous rocks such as norites and gabbro-norites.
Not everyone knows what platinum looks like in nature. The metal is represented by nuggets, plates, flakes or nodules. It is also mined in the form of skeletal forms and spongy secretions measuring 0.05−12 mm. Placers of the precious mineral are formed as bedrock deposits and rocks are destroyed. Grains of a flattened and lamellar appearance are found far from the primary sources.
Placer deposits are less common. They are usually explored by the method of spot testing. Platinum nuggets are mined in mines.
Since 1805, platinum has been produced in powder form from South American ore. Over time, the method of obtaining the mineral has changed:
- Platinum metal concentrate is dissolved in aqua regia.
- Ethanol and sugar syrup are then added to get rid of excess HNO3. Ammonium hexachloroplatinate is released with ammonium chloride.
- The dried sediment is calcined at +800−900 degrees.
The resulting sponge platinum is purified. It goes through all the previous processes again and is then melted into ingots.
Platinum black is obtained when solutions of metal salts are reduced by chemical and electrochemical methods.
Lead Density
The purer the gold, the less hard it is, so in the past the yellow metal was bitten to test. This method is unreliable. The jewelry can be made of lead, covered with a very thin layer of gold. Lead also has a soft structure. You can try to scratch the jewelry from the wrong side, and underneath a very thin layer of precious metal you may find base metal.
The density of the element of the periodic table - lead and its brother - gold is different. The density of lead is much less than gold and is 11.34 grams per cubic centimeter. Thus, if we take the yellow metal and lead of the same volume, then the mass of gold will be much greater than that of lead.
White gold is an alloy of yellow precious metal with platinum or other metals that give it a white, or rather matte silver, color. There is an opinion in everyday life that “white gold” is one of the names for platinum, but this is not so. This type of gold costs a little more than usual. In appearance, the white metal is similar to silver, which is much cheaper. The density of such elements of the periodic table as gold and silver is different. How to distinguish white gold from silver? These precious metals have different densities.
Silver is the least dense material of all those discussed in the article.
The density of gold is greater than that of silver. Its density is 10.49 grams per cubic centimeter. Silver is much softer than white metal. Therefore, if you run a silver item across a white sheet, a mark will remain. If you do the same with white precious metal, there will be no trace.
Distribution and use of cast iron
Cast iron came into widespread use many years ago. This is due to the fact that the material is quite simple to produce and has quite attractive performance properties. The following varieties of this material are distinguished:
- High-strength: used in the production of products that must have increased strength. A similar structure is obtained by adding magnesium impurities to the composition. It is highly resistant to bending and other impacts not associated with variable loads.
- Malleable cast iron: has a structure that is easily forged due to its high ductility. The production process involves annealing.
- Half: has a heterogeneous structure , which largely determines the basic mechanical qualities of the material.
The specific gravity largely depends on the production method used, as well as the chemical composition. The properties of cast iron are affected by the following impurities:
- When sulfur is added to the composition, the refractoriness decreases and the fluidity value increases.
- Phosphorus allows the material to be used for the manufacture of various complex products . It is worth considering that by adding phosphorus to the composition, strength is reduced.
- Silicon lowers the melting point and significantly improves casting properties.
- Manganese can increase strength and hardness, but adversely affects casting properties.
When considering cast iron, it is worth paying attention to the following information:
- Gray cast iron grade SCh10 is the lightest of all produced: 6800 kg/m 3 . As the grade increases, the specific gravity also increases.
- The malleable variety of this metal has a value of 7000 kg/m3.
- High strength has a value of 7200 km/m 3.
The density of metals, like other materials, is calculated using a special formula. It has a direct bearing on specific gravity. Therefore, these two indicators are often compared with each other.
