This article accompanies the textbook The Real World of Chemistry 6th ed by Lois Fruen Kendall/Hunt Publishing ISBN 0-7872-9677-5

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In ancient Egypt, the metal most often refined was copper. Copper was an important metal for the ancient Egyptians, because it could be easily worked and shaped into weapons and tools.

Mark Lehner, Director of the Giza Mapping Project, is excavating the workshops and kitchens of the workers who built the pyramids. At the site, he found slag from ancient copper production. The slag had been heated so hot, it vitrified. To make fires hot enough to vitrify copper slag would have required vast amounts of wood. In fact, Lehner found that the floors of the site were covered with very deep, thick velvet carbon ash from the burnt wood. Lehner said that the cutting of wood to produce such huge amounts of ash contributed to the deforestation of Egypt at the time when the pyramids were being built.

To produce copper, the ancient Egyptians heated copper (II) oxide (CuO) in ceramic moulds over burning charcoal on the open hearths. The ceramic moulds served as smelting crucibles.

The Egyptians also could have produced copper from malachite (CuCO₃^.Cu(OH)₂). This required even higher temperatures than smelting CuO—around 1100°C. Dr. Lehner believes the ancient Egyptians could have been obtained temperatures this high at Giza (Lehner The Complete Pyramids 173).

To produce the very hot temperatures, metalworkers probably used long tubes to blow air into the molds. While no such tubes have been found at Legner’s site, relief art from a tomb in Sakkara, which was built at about the same time as the pyramids, shows metalworkers blowing through tubes to produce a hotter fire.

The ancient Egyptians discovered that copper ore melted more easily and the resulting metal was stronger if the copper was alloyed with another metal, such as arsenic or tin. Copper with arsenic was the first alloy to be made. Arsenic is a natural component of some copper ores, such as olivenite (Cu₂AsO₄OH), so early copper smelting would have accidentally produced copper-arsenic alloys. Later, arsenic pigments such as orpiment (As₂S₃), were purposefully added up to 6% (Lambert 176 and Orna 22). However, working with arsenic could not have been easy or pleasant. During smelting, poisonous clouds of arsenic would have been produced. This is why early metal workers in other places replaced arsenic with tin and began making bronze (Bowman 75, 79). Bronze production in Egypt, however, was delayed because Egyptian copper came from the Sinai where there was no tin (Walker 277).

Ancient Egyptians added flux to the copper ore to produce molten slag. The flux contained silicates and iron oxides that lowered the melting temperature of the slag, so it turned to liquid at the temperatures of the charcoal fires. The advantage of molten slag was it could be tapped off. We know the iron oxides were added to the copper produced by the Egyptian metal workers because of the amount of iron (0.3% opposed to 0.03% in native copper) found in the copper remnants (Lambert 175).

The chemical composition of the copper produced at Giza was determined by atomic absorption spectrometry (AAS). AAS works like a sophisticated flame test, similar to the flame tests done by high school chemistry students to identify elements in different salts. In ASS, a small sample of metal from the object being tested is reacted with an acid. A solvent is added, and the solution is evaporated to remove the solvent and acid. The residue is redissolved, and the solution is sprayed into a flame in the instrument. The wavelengths of light produced are characteristic of elements present in the sample. The intensity of the light indicates the percentage of each element. AAS has shown that the tools and weapons made at Giza were from pure copper and arsenical copper (Bowman 79).

Evidence of copper grinding and pigment making was also found at Lehner’s sire. Copper pigments were used to paint statues and tombs.

I was fortunate to meet with Dr. Mark Lehner at his excavation site near the Giza pyramids. Lehner pointed out the copper works, took out his trowel to show the black velvet ash that covers the site, scraped the clay bed to reveal the chalk lines that mark the remains of buildings, displayed the site maps, and hiked us over sand dunes for a view of the entire area.

Bowman, Sheridan ed. Science and the Past. Toronto: University of Toronto Press, 1991.

Lehner, Mark. Chicago Symposium lecture. 23 Oct. 1999.

---. Lecture Giza Plateau. 21 Feb. 2000.

---. The Complete Pyramids. London: Thames and Hudson, 1997.

Orna, Mary Virginia. "Those Mysterious Pigments: The Chemistry of Ancient Art." Today’s Chemist. Dec. 1991: 20-24.

Plambeck, James. Introductory University Chemistry: Metals: Industrial Process Copper and Bronze. 5 Feb. 1996. www.chem.ualberta.ca/courses/plambeck/p102/p02262.htm.

Walker, Robert. "Corrosion and Preservation of Bronze Artifacts." Journal of Chemical Education: The Art of Chemistry. Apr. 1980: 277-280.