Rediscovery of the Elements — a Historical Sketch of the Discoveries
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REDISCOVERY OF THE ELEMENTS — A HISTORICAL SKETCH OF THE DISCOVERIES TABLE OF CONTENTS incantations. The ancient Greeks were the first to Introduction ........................1 address the question of what these principles 1. The Ancients .....................3 might be. Water was the obvious basic 2. The Alchemists ...................9 essence, and Aristotle expanded the Greek 3. The Miners ......................14 philosophy to encompass a obscure mixture of 4. Lavoisier and Phlogiston ...........23 four elements — fire, earth, water, and air — 5. Halogens from Salts ...............30 as being responsible for the makeup of all 6. Humphry Davy and the Voltaic Pile ..35 materials of the earth. As late as 1777, scien- 7. Using Davy's Metals ..............41 tific texts embraced these four elements, even 8. Platinum and the Noble Metals ......46 though a over-whelming body of evidence 9. The Periodic Table ................52 pointed out many contradictions. It was taking 10. The Bunsen Burner Shows its Colors 57 thousands of years for mankind to evolve his 11. The Rare Earths .................61 thinking from Principles — which were 12. The Inert Gases .................68 ethereal notions describing the perceptions of 13. The Radioactive Elements .........73 this material world — to Elements — real, 14. Moseley and Atomic Numbers .....81 concrete basic stuff of this universe. 15. The Artificial Elements ...........85 The alchemists, who devoted untold Epilogue ..........................94 grueling hours to transmute metals into gold, Figs. 1-3. Mendeleev's Periodic Tables 95-97 believed that in addition to the four Aristo- Fig. 4. Brauner's 1902 Periodic Table ...98 telian elements, two principles gave rise to all Fig. 5. Periodic Table, 1925 ...........99 natural substances: mercury and sulfur. The Fig. 6. Separation of Rare Earths ......100 progenitor of this theory was the Arabian Figs. 7-10. Radioactive Sequences 101-104 alchemist Geber. A thousand years ago he explained that mercury could contribute “fluidity,” and sulfur “combustibility”; later alchemists — principally Paracelsus — added INTRODUCTION salt, which would confer “fixity.” Robert Boyle, best known for his or over five millennia the mysterious “Boyle’s Law,” in the 1600s discussed in “The transmutation of substances into new Sceptical Chymist” the standards by which a Fones — the enigmatic metamorphosis of substance could be adjudged as an element. sand and clay into glass and pottery, the He realized that Aristotle’s four elements and mutation of larvae into flies, the basic riddle the alchemists’ three principles could not be of life itself — suggested to the human mind correct, because they were never proven to that deep-seated principles were responsible. compose, nor could they be extracted from, any Beginning with recorded history, the ancient other substances. He expounded: Egyptians were deeply preoccupied with life “I now mean by Elements, as those and death and sought answers through Chymists that speak plainest do by their medications, pharmaceutical preparations, and 1 Principles, certain Primitive and Simple, or thought — from philosophical Principle to perfectly unmingled bodies; which not being materialistic Element — was made by made up of any other bodies, or of one Lavoisier, who in his Treatise of 1789 realized another, are the Ingredients of which all those that since water was manufactured by the call’d perfectly mixt Bodies are immediately combination of “inflammable gas” (hydrogen) compounded, and into which they are ulti- and “vital air” (oxygen), then water must be a mately resolved: now whether there be any compound. From this remarkable intuition all one such body to be constantly met with in all, else followed. Lavoisier listed 31 materials and each, of those that are said to be which he proposed — correctly — were the Elemented bodies, is the thing I now true elements, including sulfur, iron, carbon, question.” copper, molybdenum, etc. Recognizing that In other words, if something was an “inflammable air” and “vital air” were element, then it must be proven by experiment elements, he dubbed them with the names by to be separable as basic material which could which we know them today. He even not reduced to any more fundamental stuff. recognized that “radical muriatique” (chlo- Since this decisive experiment was sorely rine), “radical fluorique” (fluorine) and others lacking, the “chymist” had no recourse but to which had not been yet prepared in the rely on the old theories. He was still stumbling elemental form were also elements. Lavoisier over the basic flaw — he could not abandon had peeked beyond the dining room into the the outmoded concept that elements were kitchen. Aristotelian principles reflecting essences Lavoisier’s insight opened the immediately manifest to the eye and other cupboard doors, out of which tumbled a senses. He had merely renamed the old myriad of wondrous oils, sugars, and spices. principles — the Aristotelian “hotness” had Excitement grew in the scientific community simply evolved to alchemical “combus- as, one by one, new condiments were tibility.” discovered pell-mell in this pantry. By the The truth was much more subtle — middle of the nineteenth century it was and surprisingly simple. True elements were recognized that the cabinet was even commonly ingredients to worldly materials. organized in tidy shelves and bins, and soon Only rarely did an element present itself in Mendeleev was even predicting new simple form in nature — such as gold. It was flavorings not yet tasted or dreamed of! like trying to identify the flour, sugar, salt, By the early twentieth century, ninety- lard, and eggs that went into the baking of a two continuous cubicles had recognized, each cake from the smells emanating from the final with an identified staple, and the scientists had concoction, often when one had never seen cooked up thousands of new culinary formu- these original ingredients! More commonly, lations. But the cuisine did not stop there! The an element was in combined form in nature, nuclear chemist synthesized new makings, and the extraction of these material elements new racks were built in the pantry, and eluded the scientist. The modern recognition eventually the list of condiments expanded to of element had to await a true genius who over one hundred. could wonder about the original recipe of the This, then, is the story of how that Cosmic Baker. kitchen was explored. The giant step in this evolution of 2 1. THE ANCIENTS durable metal could be formed — bronze. (prehistoric times-500 A.D.) However, tin was originally scarce, and tin sources were sought out and developed. Lead was soon discovered — as a softer and heavier The Story of the Elements begins with metal, it could be used as weights, water Stone Age Man, who had discovered how to pipes, writing tablets, and coins. Silver was prepare tools out of wood, bone, and rocks. usually found in nature in compounds (such as He discovered that wood was good for silver sulfide); for a while metallic silver was preparing pliable implements, such as shafts actually more expensive than gold until and spears. Bone was excellent for fine effective smelting methods were discovered. instruments such as needles. Rocks could be The discovery of iron was delayed because of used for kitchen utensils (for example bowls, its corrosion and the difficulty of smelting it. typically from rough igneous stones), and for About 1500 B.C., the beginning of the Iron tools and weapons (such as scrapers and Age, the Hittites developed effective spearheads, usually flint). These materials procedures for extracting iron. Mercury was were effective but all suffered from their easily obtained from its ore by mere heating tendency to splinter or break — they were all — sometimes mercury “sweat” could be seen brittle. Man eventually stumbled upon metals on cinnabar. Nevertheless, it was more which had unique properties — they were casually mentioned in ancient literature since simultaneously malleable and strong — they it not utilized in tools and implements; it was could be used for tools and weapons, could be used in more esoteric applications, such as prepared under heat, and were not brittle. “medicines.” Well over ten thousand years ago The Old Testament mentions six metals were adopted by Man. The ancients metals. As early as about 1200 B.C. (Numbers recognized that metals were very special and 31:22) reference is made to firing gold, silver, they attributed these metals with special bronze (copper), iron, tin, and lead. In Ezekiel magical properties and spirits. The discovery 27:12-13, dated about 600 B.C., Spain is of metals was so important that the mentioned as a rich source of silver, iron, tin, anthropologists differentiate the “Stone Age” and lead; and Greece is described as a from the subsequent “Bronze Age” and “Iron provider of bronze. Age.” Ancient civilization, which had devel- Seven metals were known to the oped a sophisticated technology of materials, ancients — gold, copper, tin, lead, silver, iron, attributed Gods as being responsible for the and mercury. The first metal to be discovered special properties of metals. Since there were was probably gold, because of its beauty and seven metals known to the ancients, and since its resistance to corrosion, and was adopted there were seven heavenly bodies, it was for jewelry and ornaments. The first metal of apparent that each of these heavenly bodies practical use was copper, perhaps 10,000 B.C., was associated with one of these metals. Since which could be beaten into tools and each of these heavenly bodies was a God with ornaments. Elemental copper was occasionally a distinct temperament, they found that each found in the form of nuggets, and later of these elements was clearly connected with (roughly 5000 B.C.) could be smelted from one of these personalities: ores. About 3000 B.C., it was found that when Gold — the Sun, or Sol, with his copper was mixed with tin a harder, more 3 golden radiance icosahedron.