Iron Age - Part 1

The media constantly report that the age of plastic has come, and silicon civilization is flourishing around. However, the reality is different: we have been living in the Iron Age for more than three thousand years. You can also add that the nineteenth century, i.e. the age of steam and electricity (since electricity is still mainly generated by the power of the flow of water vapor), continues in terms of energy.

The Roman poet Ovid, in his Transformations, described the mythical epochs of mankind, largely in accordance with development of civilization. So, after the happy ages of gold and silver (here the author had a fantasy, because it was a stone period), the age of bronze, one of the alloys of copper and tin, reigned. At that time, Hercules, Theseus and the Argonauts lived, and the heroes of Homer, dressed in bronze armor, fought under the walls of Troy with bronze swords. Archaeologists call this period the Bronze Age. After her (after Ovid) ...

... the age of hard iron has come

When did it start? It is difficult to answer this question. they come from the 1st millennium BC, and maybe even earlier. And it was not "any" iron, but heavenly, strictly meteoric origin (XNUMX). It is not surprising that they were treated as a real gift from the gods and respected accordingly.

1. A fragment of the largest Polish iron meteorite found in the suburbs of Poznań (Morasco). The specimen is in the AMU Earth Museum (author: Wikimedia/MOs810)

With clean with earthly iron a man met when he began to receive metals from ores, and not from nuggets. ,: at temperatures achievable at that time in furnaces (up to a maximum of 1000 ° C), these metals melted and could be cast, and their softness made it easy to work with forging.

Z iron it wasn't that easy. Firstly, it melts at a temperature exceeding 1500 ° C, and secondly, when cold, it is hard and cannot be molded by millennium-old methods. Initially, it was a troublesome by-product (copper and iron ores are often adjacent to each other) - a piece of spongy, hard mass remained at the bottom of the furnace. It was iron made from reduced oxides from ore. By chance, the ancient smith blacksmith began to process the resulting slate (from Latin, meaning wolf) even before it had cooled (2). This time metal is easy to work with. Although by today's standards it was very low-quality iron, it turned out to be harder than all the metals known at that time.

2. Blacksmithing has been an important profession for thousands of years (Author: Wikimedia/Jorgeroyan)

The hardness of iron depends on the amount of carbon dissolved in it. (it came from the charcoal used for smelting), and this, in turn, from the temperature of the smelting - increases with it. Low-carbon iron was obtained in primitive furnaces (carbon content did not exceed 0,5%).

However, the technology continued to develop. Better furnaces have been developed to achieve higher temperatures so that more carbon is dissolved in the iron. When its content reached about 1%, a person first met him. was. The blades made from it did not dull quickly, and besides, it could be hardened, which additionally increased its hardness. Since then, the new metal has been rapidly replacing brown. When was this breakthrough? Around the middle of the second millennium BC in the territory of modern Syria and Anatolia (Turkey). From there, steel spread throughout the then world, although in different parts of it this invention was carried out independently of each other (for example, in India and China).

But why irondespite problems with its production, was replaced by bronze? This time we will give the floor to Bolesław Prus, who in Pharaoh described the advantages of the new material as follows: “one of the Egyptian officers drew his bronze sword and held it as if about to attack. Then Sargon raised a steel sword, struck and cut off a piece of the weapon to the enemy.

Metal of war

The novel is set in the 3rd century BC, but prior to that, better weaponry meant advantage on the battlefield. It is probably no coincidence that the invention of steel production was invented by the Hittites, a people of warriors. After them, it was adopted by no less courageous Assyrians, whose envoy Sargon so clearly showed the young heir to the Egyptian throne the advantages of a new weapon. Since then, iron has been forever associated with war, it has been dedicated to the gods who watch over this area of ​​life, and (XNUMX).

3. The surface of Mars covered with iron oxides (from NASA resources). The astronomical symbol of the planet Mars and the alchemical symbol of iron depict a shield and a spear - attributes of the god of war

Centuries passed, the technology of smelting and processing improved (in Poland already in the XNUMXth century BC. metallurgy). Their secrets were carefully guarded, and their successful inventions were widely known, such as perfect damask. In addition to small primitive smokehouses, large furnaces were increasingly built for smelting. In medieval Europe, it was possible for the first time to reach the melting point of iron and - instead of the spongy mass lying at the bottom of the hearth, liquid metal flowed out of the furnace, i.e. salad. However, this did not cause admiration: an alloy with a high carbon content (cast iron) was brittle and could not be forged, suitable only for castings (it is still used for this purpose today).

The breakthrough in steel production occurred in the XNUMXth and especially in the XNUMXth centuries. At first it was used for smelting coke (degassed hard coal) instead of coal. This happened in England, where the steel industry contributed to significant deforestation in the country (the demand for coke was an incentive for the rapid development of the mining industry). coal). The development of methods for producing steel from smelted iron by removing excess carbon and other additives (phosphorus, sulfur, silicon) made steel cheap and available in large quantities, which in turn initiated its widespread use as a structural material.

Technological processes of the XNUMXth century - Bessemer, Thomas, and especially Siemens-Martin - to this day they are the basis of steel production (of course, they have been improved in many ways). Although trial and error is currently not practiced, and the processes of smelting and steel processing are studied by specialists in various fields, there is still an added element of art in metallurgy. Specialists in this field can be compared to chefs who, using the right spices, can get delicious dishes. In this case, the function of spices is performed by alloy additives (that is, various elements), and ready-made dishes are alloys “for all occasions”.

Metal #1

Hardware this is the basis of our civilization, let the numbers speak for themselves. In 2019, 1300 10 million tons of pig iron were smelted worldwide, of which about 1900% went to the production of cast iron products, the rest was processed into steel. About 10 million tons of steel were produced (the difference is steel scrap added during the processing of pig iron). The “Steel Plant of the World” is China, which supplies more than half of the products (Poland has about 2 million tons). Annual metal production number 80, i.e. aluminum, is less than XNUMX million tons, which, compared with two billion tons of steel and iron, fully proves that we are still living in Iron age (4)

4. World steel production is two billion tons per year.

We have a lot of iron on Earth, the surface layer contains 5,6%, which puts this metal in 4th place (after oxygen and clay). If we take the Earth as a whole, then iron is in the lead, accounting for almost a third of the mass of the globe (in the center of the planet there is an iron-nickel core with a diameter of almost 7000 km). In the universe, iron is the 6th most abundant element, as well as the heaviest element that can be produced in the core of a star (heavier ones are created as a result of cosmic cataclysms - supernova explosions).

Free iron on earth occurs occasionally in the form of small nuggets and. However, iron minerals are plentiful: hematite Fe₂O₃, siderite FeCO₃, magnetite Fe₃O₄ limonite (hydrated oxides, the so-called swamp ore) is the most commonly mined ores of this metal, and pyrite, which imitates gold FeS₂ it is used to produce sulfuric acid (5).

5. A reddish color at the bottom of a stream signals the presence of ubiquitous iron compounds.

The living world has also taken advantage of the benefits of iron, which is essential for all organisms. Iron ions are at the center of two important proteins: hemoglobin, which transports oxygen, and myoglobin, which stores life-giving gas in the muscles. Also, many of the enzymes responsible for the oxidation and reduction reactions function due to the presence of iron ions (by experimenting, you will learn why this happens). The body of an adult contains about 4 grams of iron, and its deficiency causes anemia. Rich sources of easily digestible iron are: meat, liver, egg yolks, nuts, milk and legumes.

Mutual transformations

Ferrous and ferric salts are available from your laboratory. An example of the former is FeSO sulfate.₄and the other is chloride FeCl₃ (both as hydrated salts). In the case of FeCl₃ be especially careful: its solutions are caustic and leave brown spots that are difficult to remove. Therefore, protective gloves are required and tests are carried out on a tray. Prepare solutions of both salts and pour them into test tubes. Solution containing Fe ions²⁺ has a light green color in the case of Fe cations³⁺ color yellow (6). Add a small amount of NaOH sodium hydroxide solution to each tube. In both cases, the following deposits are formed: Fe(OH)₂ grey-green, and Fe(OH)₃ - russet (7)

6. Colors of solutions of iron salts.

7. Precipitation of iron hydroxides

For test tubes with Fe(OH) sediment₂ add a few drops of 3% hydrogen peroxide solution N₂O₂ (hydrogen peroxide used as a disinfectant). The precipitate quickly turns red-brown (8):

2Fe(OH)₂ +H₂O₂ → 2Fe(OH)₃

8. Iron (II) hydroxide is rapidly oxidized to iron (III) hydroxide.

Pour a few drops of FeCl solution into a test tube with water.₃ so the color is only light yellow. Add a small amount of potassium iodide solution KI, it will immediately darken the contents. Now add sodium thiosulfate solution. _Na2S2O3. The contents of the vessel were almost discolored. Finally add a few drops of NaOH solution. The precipitate formed has a color ... surprisingly, greenish. What reactions took place in the test tube?

First, Fe ions³⁺ oxidized iodides to free iodine (darkening of the solution), naturally, they themselves were restored. The addition of thiosulfate again caused the reduction of iodine to colorless iodides, and under the action of the base a precipitate of Fe(OH) was formed.₂.

This easy transition, as it were connected with Ovid's Transformations, of Fe(II) ions into Fe(III) and vice versa underlies their biological activity.

Iron, steel, cast iron

Most often, when we talk about iron, we mean steel. Pure iron is almost never used. Iron with a small amount of impurities (ARMCO iron) is used as a magnetic material. Steel is an alloy with a carbon content of 1,7-2,1%. If there is more carbon, it separates in the form of graphite and forms cast iron.