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Chemistry and the Roots of Civilizational Technology - Metallurgy (Metal Forming) .. From the Prehistoric Chemist to the Chemical Philosopher: The Seeds

Chemistry and the Roots of Civilizational Technology

With the advent of civilization, chemical technology matured and it became possible to develop techniques that required special permanent structures such as furnaces for smelting metals), and it became possible to record, repeat and improve chemical processes. From the artifacts that remain to this day, we can form - step by step - a picture of the methods used at that time. The longest-lived of these artifacts are metals, and metallurgy (metal forming) is the first chemical technology whose history can be reconstructed with some confidence.

Metallurgy (metal forming)

Metals were used by practically all civilizations even before they used other apparently primitive technologies such as the wheel. But most metals react with oxygen, sulfur and halogens - such as chlorine, fluorine and iodine - and occur in nature as ores, that is, complex mixtures of salts and silicates such as feldspar, pyrite and bauxite. Silver and gold, on the other hand, do not react significantly, and so can be found in nature as pure metals, such as gold nuggets that were found in rivers during the gold rush in the United States in 1849. Copper can be found as deposits of pure metal, but it is most often found in raw form. These three metals can be manufactured using simple techniques such as hammering and extracted using easy techniques such as collecting.

Copper, Silver, and Gold

Copper was probably the first of these metals to be collected, due to its wide spread compared to the other metals. Jewelry made of copper artifacts was found in northern Iraq, dating back to approximately 9,000 BC (6), and was probably used for decoration. It was found that the fortified burials of the indigenous people in North America, dating back to 2000 BC. It contains spearheads, chisels, and bracelets of copper. Pre-Columbian settlers in Ecuador formed pure copper by hot hammering, and made small axes, bells, and copper sewing needles (7). Copper also appears in the early remains of settlements in ancient Egypt, Mesopotamia, and Indochina.

Gold alloys are relatively soft, hence the legendary test of gold coins by biting and they could be hammered together to form slabs. This property made gold desirable as an ornamental material in addition to its color, but it was useless for anything else. The art of using gold to make rust-resistant electrical connections and to coat teeth has recently developed. This makes the amount of human suffering that went into searching for gold seem ridiculous for its absurdity. In Egypt, gold was extracted and manufactured by slaves. Silver may be found alloyed with gold to form a substance called electrum. There are several methods that can be used to separate the silver from this alloy and recover the gold. However, the oldest method is likely to be to heat the electrum in a crucible with ordinary salt - sodium chloride. With time, heat, and repeated processing, the silver turns into silver chloride and comes out with the slag, the layer of impurities that floats on top of the molten metal during the process. However, silver was not always an undesirable product. In Egypt, between the thirteenth and fifteenth centuries B.C., silver was rarer and more expensive than gold (8). By 3,000 B.C., the Sumerians may have discovered that, while heating copper to make it more malleable, more copper could be recovered from a fire if the metal was heated with certain types of earths and stones—that is, with certain oxides. These earths or oxides were the raw materials of the metal, and the process they discovered—smelting—reduced the salts of the metal to the pure metal by the action of carbon in the coals of the fire. The process of changing the salts of the metal to the pure metal is known as reduction because the metal, without the oxygen, halogens, or sulfur that accompany it in its salts, weighs less than the raw material. Finally, metal makers learned to distinguish different metal-bearing ores by color, structure, weight, flame color, and odors given off when heated, such as the garlic-like odor of arsenic ores, and could produce the desired materials on demand.

Bronze

The Sumerians also mixed copper with tin to make a new material, bronze. They found that the new material was relatively easy to cast and much harder than copper alone. Bronze could be used to make longer-lasting tools such as hoes, shovels, and knives that retained their sharpness for longer periods. The discovery of bronze was so important that an entire era in history, the Bronze Age, got its name from its use. However, this term has lost its historical definition because different civilizations discovered the use of bronze at very different times. Some civilizations do not know the Bronze Age, such as Finland, northern Russia, Polynesia, central Africa, southern India, North America, Australia, and Japan. These civilizations made the leap from stone to iron. Egyptian bronze objects date back to about 3,000 years BC. In order to make bronze, the ancient Egyptians imported tin ore, most likely from Persia. Tin was also imported by craftsmen from Mesopotamia. Bronze could be made from copper and arsenic if tin had become scarce. But this industry died out (the fumes from the process probably caused arsenic poisoning, so it is likely that it was the technicians who disappeared, not the art). With bronze a picture of complex commercial relations in the Mediterranean began to emerge. In fact, there is some evidence of the Assyrians engaging in some skilled contracting work that could be described as immoral. They were a tough, cold-hearted society of warriors of both sexes who defeated the inhabitants of Mesopotamia (now Iraq, c. 1200 BC). They seem to have deceived the ancient Turks into believing that the nearest source of tin was in the Hindu Kush in present-day Afghanistan), and so they charged the Turks exorbitant prices when the metal came from a mine on the Turkish coast (9). It was later observed that the smelting of copper went better if certain earths containing iron oxide were added. Iron oxide may have been found in copper ore by chance, because the soil was found in the upper layer of weathered copper sulfide deposits. Iron oxide improved the copper smelting process because it acted as a flux: a substance that helped remove impurities by combining with them to form a floating crust or slag, while pieces of iron were formed as a by-product.

Iron

Iron was known in Egypt perhaps as early as 3,000 BC. But its name was the metal of heaven, reflecting the fact that the first samples of it were of meteoric origin. Iron was thus considered an exotic object rather than a commodity or commodity. However, samples of iron prepared by smelting (from iron ore, not from meteorites) were probably produced in Mesopotamia and northern Syria in 3000 BC. An iron foundry was operating in South Africa in 2000 BC (10).

The first iron prepared by smelting was in the form of a sponge-like mass in semi-liquid slag, because the actual melting point of iron was 1500 °C, while the temperatures that could be reached in primitive coal furnaces did not exceed 1200 °C. This product, later called Nora (*), required repeated heating and hot hammering to remove the slag. The iron was tempered by repeated cold hammering with reheating.

As time passed, workers increased the fuel and used huge bellows to raise the temperature of the furnaces. However, pure iron was softer than bronze and was considered a poor material for making weapons and some other applications that required a longer life. It was still unknown that heating iron in the presence of very small amounts of carbon would lead to To seep into the structure of the iron, it increases the strength of the material significantly.

The process of heating iron in the presence of carbon, which usually comes from the coal used in the fire, is called carburization. Hindu doctors were among the first to discover carbonized iron, or steel, and used it in surgical instruments. In China, carburization was done directly using iron ore rich in carbon.

This technique was also discovered by mysterious Indo-European tribes called the Hyksos. They used this technique directly to make better weapons, were able to invade Asia Minor, and in 1200 BC they knocked on the doors of Egypt threateningly.