Artifacts and the Electromotive Series Charles D. Mickey Texas A&M University at Galveston Galveston, TX 77553
Archaeolow is a scientific studv of man's remote Dast. and as such, invoi"es skilled and difficult work. The archaeologist functions to find out about the past of the human race in its material aspects and to study the products of the past. These aspects include the way people lived, their way of worship, their buildings, their economy, their travels, their tools, their weapons, and their art. Sometimes startling discoveries of artifacts are made. such as those in Tutankhamun's tomb or those of the ~ h r a c i a ntreasures of Bulgaria (1,2). Thus archaeology coupled with disciplines such as chemistry, geology, botany, geography, and anthropology provide the information for man's history before the beginnings of written records (3). ~-,.
According to archaeological evidence we find that thousands of years ago man made his tools-hammers and axes--out of stone. That was the Stone Age. Subsequently he discovered copper and tin, and how they could he fused to form bronze. As long as he made his tools of bronze, he was in the Bronze Age. Even then he was beginning to use the iron found in meteorites. Finally the ancient Hittites learned to Droduce and utilize iron. and as this knowledee " started to spread, more than 3,000 years ago, man entered the Iron Age (4). The vast im~rovementin all the thines that we now make of iron, from needles to supertankers, tklls the story of its importance. ~
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Metals of the Ancient Artisans
The metals gold, silver, mercury, tin, lead, copper, and iron have been used by man for so many centuries that records of their discovery are unknown. Gold was probably one of the first metals to he used by man. It occurs free in nature and is found in the silt and gravel of many streams. Since gold was rare i t was not widely used except in decorations and primitive jewelry. Copper, i t is estimated, has been in use since 8000 B.C. for making tools, weapons, utensils and decorations. I t was about 3800 B.C. that bronze, an alloy of copper and tin, was discovered. The allov was much harder andmore durable than copper and was used as a major material for tools and weapons. Probably the first winning of iron occurred when chunks of iron ore were accidentally placed with stones in fire pits where foods were cooked. The silvery iron metal was freed from the ore when the wood fire was maintained for a long period. Eventually the free metal was beaten or hammered into shapes for tools or weapons. The introduction of iron in place of bronze made tools and weapons much cheaper, for
iron is more plentiful than copper. Therefore, the majority of tools and equipment were, in fact, made of the less ~recious. less expensive iron. Gold versus Iron Artifacts
The fact that gold occurs free, is pleasing in appearance, and is easily worked accounts for its earlv use for iewelrv and ornamental purposes. However, today & in the past, iroi is more valuable than gold, although less costly. Today, of course, iron forms the basic framework of our society, being used in transportation, buildings, bridges, machinew, and tools. In ancient societies as well, iron u,as used more extmsively than gold fur making wenpons and tools. Thereiure. logic u,ould indicate that the archacnl~~gist should find more iron artifw ts than gold. Why then, are the must significanr artifacts f(,und hg arrhaeologisu made of gold instead of iron? Metallic Character
When we think of metal, we are almost certain to think of something hard, heavy, and perhaps shiny. But there are metals that are neither hard nor heaw. Some metals are so light that they float on water, and some are so soft that they flow like oil. Chemically, we know that afew metals are found free in nature while others are never found in the free state. A more detailed discussion of the properties of metals can he found in the article by R. T. Myers (5). Inasmuch as the physical properties of metals depend largely upon the nucleus and the inner electron shells of atoms, its chemical properties are largely dependent upon the mobility of its valence electrons. Remember, this arbitrary distinction between the origin of chemical and physical properties is used only as a method of classifying the many properties of elements. In reality, the two types of properties are interdependent upon each other. Metals are ElectropositiveElements
Some elements have the tendency to lose or lend their valence electrons and to form positive ions. These elements are classified as metals. On the other hand, the elements that tend to accept electrons and become negative ions are classified as nonmetals. Chemlcal Reactions of Metallic Elements
Some metals react with water. Very active metals such as lithium, sodium, ~otassium.and calcium react with cold water forming hydroxibes and releasing hydrogen gas:
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2K14 + 2H20111- 2KOHw + H2ig) Less active metals like magnesium, zinc, and iron react with steam, to form oxides or hydroxides and hydrogen gas: 3%) + 4HzOi,1- FeaOw + 4 H w Many active metals react with dilute, nonoxidizing acids to form salts and hydrogen gas:
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Hvdroeen ,. is nlaced in the list to senarate those metals which displace hydnggrn from acids, frum those which arc Iesi active and will nut replare hydrogen from acids. The metals listed ahovr hydrogen in the artivity series will replace hydrugen from acids: those below hydrugen will not rract with an acid to release hydrogen gas. In this activity series, metals are arranged in
