Chemistry's Lively History

chapter ONE ca. 100,000- 300 BCE: Prehistoric Chemist to Chemical Philosopher— the Seeds

Because this section is during the prehistoric era (before written records), the authors will attempt to describe this history based on evidence of a "chemical nature".  These include instances when properties of materials and how they interact are observed.  Some of these noted by that authors are:

cooking, the process of breaking chemical bonds to make the food easier to digest

soem form of primitive medicine based on skull evidence

mixing of different substances to as pigments or paints as found in cave paintings

making pottery by baking clay, "a chemical process that transforms loose, liquidy hydrated silicates into a strongly bonded network" (mesolithic or middle stone age)

make fire by rubbing sticks, perhaps the "first controlled chemical reaction", make clay, weave materials, and hammer copper into various tools (neolithic or new stone age)

4000 BC, Civilization Begins

Metallurgy:

Most metals are found bonded to other elements in the form of ores and silicates.  Coper, gold, and silver, however, can be found relatively abundantly in pure form.  Copper was hammered into various tools.  Gold, because it is a soft metal, was used mostly for decorative purposes as did silver.  Silver and gold can be found sometimes alloyed in the form of the ore electrum.  Evidence shows that electrum was heated with various salts to separate the silver as silver chloride which floated off in the slag.

3000 BC, the Sumerians discover smelting.  Ores of copper were heated over rocks and more of the pure copper metal can be retrieved.  Charcoal in the heating process, containong carbon, reduced the metal ions to the pure elemental state.  Because the metal retrieved weighed less than the ore (after having separated the metal from oxide, sulfide, and halide ions), this process was called "reduction".

BronzeAge 

The Sumerians found this alloy of copper and tin easy to cast and harder than copper. Some cultures skipped the bronze age entirely and went straight to the iron age.  Iron was, perhaps, discovered when iron oxides mixed in the smelting of bronze producing pure iron.

Iron Age

To  produce fairly pure iron (not the spongy slag), higher termperatures were required than burning charcoal can achieve (1500 celsius versus 1200 celsius).  Repeated heated and hammering resulted in a more pure form but still softer than bronze.  Later discovery of carburizing (incorporating some carbon into the iron) led to harder iron metal.

Evidence of familiarity with chemical compounds, mostly salts either extracted or made, was present in the form of a tablet left by a Sumerian physician listing such compounds as soda ash or sodium carbonate, ssodium chloride, nitrates, ammonium chloride, etc.  There is evidence that water and ethanol may have been used to extract some of these compounds.  Ethanol would have been produced through fermentation, "making fermentation one of the oldest chemcial processes".

Dyes and pigments were also part of their forays into using substances for a specific function.  Plants like indigo and saffron were used to extract purple and yellow pigments and dyes.  Some of these dyes were also extracted from insects and mussells.  These dyes are organic in nature but inorganic salts were also used as mordants, susbtances that help the dye bind to the protein of the fabric (wool was the most common fabric).

Glass, as early as the neolithic age

Glass can form by the heat of lightning or volcanic eruptions metling and fusing silicates like sand.  The earliest artificial production of glass involved mixing sand with sodium cabronate to lower the temperature required to melt and fuse sand to make glass.  This made glass somewhat soluble in water, however.  Later calcium oxide was used as the flux which reduced the water solubility of the glass.

Mummification getes a special mention.  Part of this process involves preparing a solution of natron (a sodium, aluminum, silicon, oxygen salt) to kill bacteria and dehydrate cells.

With the advent of civilization, philosophers thrived.  The primary thrust of thinking is the fundamental composition of matter.  Many of philosophical discussions centered around what basic substance make up matter.  The hypotheses ranged from matter being composed of one basic substance )the Ionian philosophers in particular including Thales after whom thallium was perhaps named?).  Air, seed, etc were some of the "primal substance" put forth by these early thinkers of chemistry.  Pythagoras of Phythagorean theorem fame got in on the discussion noting that matter is made of five elements representing 5 geometric solids, injecting soem mathematical aspect to the whole discussion.  Then came Empedocles with his four-basic substance idea that matter is composed of air, water, fire, and earth.

The conejcture closest to what we now know of the fundamental building blocks of matter came from Democritus as most chemistry students have been told.   This book claims that the idea likely came from Democritus' teacher, Leucippus:

"The essence of the theory was that matter is made up of an infinite number of solid atoms of elements in constant motion. These atoms were thought to form materials with characteristics determined by the atoms’ shapes (for instance membranes were woven from hook- shaped atoms)— an idea that still had appeal in the chemical philosophies of Western Europe in the 1600s."

Plato expounded on Empedocles four elements:  "Plato accepted the notion that all materials were made of different proportions of the elements, but he refined this idea by adding that under the right circumstances, materials could, be changed into one another or undergo transmutation."  He supported these thoughts with well-catalogued observations of matter."

Artistotle also expanded on the four-element hypothesis but unlike the previous philosphers, "used observation as well as pure reasoning to arrive at his ideas".  The book attributes the earliest greatest influence on the development of chemical thought on Aristotelian philosophy:

"Though Aristotle did not engage in systematic experimentation, his reasoning from observation represents an application of inductive logic, which has a more intuitive appeal than purely deductive reasoning when applied to natural phenomena, and this probably helped the general acceptance of his ideas."