A.1 Gold - Elements Known in Antiquity

Karl Marx wrote: "Gold is in fact the first metal that man has discovered".

This is really so. Gold articles were found in excavations together with stone tools dating from the Neolithic Age. But in those times people, evidently, used gold found by chance. Only after the emergence of classes in society first attempts were made to mine gold. The explanation is simple. Gold was particularly suited to play the function of money due to its properties of immutability, easy divisibility, and high cost.

As an ornamental material, gold began to be used from time immemorial. During excavations of pyramids of all dynasties in Egypt archaeologists found in great numbers not only gold jewelry but also household articles.

Gold was known not only in Egypt. As early as in the 10th century B.C. it was used in China, India, states of Mesopotamia. In Greece gold coins circulated as far back as in the 8th-7th centuries B.C. In Armenia gold coins appeared in the 1st century B.C. Thus, gold was known to the peoples of ancient states in Europe and Asia. The oldest gold mines were found in India and Nubia (North-East Africa).

The processes of gold purification known in antiquity did not yield the pure metal but usually alloys consisting of gold and silver which were named azem. A natural gold-silver alloy—electrum—was also known.

No other metal has played so sinister a role as gold in the history of mankind. Wars were waged, nations and states were annihilated, monstrous crimes were committed for the sake of gold. But possession of gold did not bring peace to man. On the contrary, sorrow and fear of losing this treasure filled his soul.

The alchemic period between the 4th and the 16th centuries was a gloomy one in the history of the search for gold. The efforts of alchemists were directed towards the search for the "philosophers' stone" which, they held, possessed the property of transforming base metals into gold. Alchemy did not start from scratch but had important precursors. Egypt's fast rise was due to the fact that Egyptians possessed the secret of gold extraction. It was also known that iron articles that remained in copper mines for a long time became coated with copper. Iron was believed to transform into copper. If it was so, why could not other metals be transformed into gold? Native lead sulphide almost always contains an admixture of silver, which could sometimes be extracted. Could not silver be formed on lead? And, finally, progress in alchemy Was facilitated by the idea about the unity of matter according to which all substances consist of the same components in different ratios.

All the attempts to find the "philosophers' stone" turned out to be unsuccessful (as one should have expected), although many alchemists gave their lives for the idea. All reports about the discoveries of methods of preparing gold from other metals were pure charlatanism.

Alchemy was still flourishing in Europe when the first Spanish conquistadors set out for South and Central America. In the land of Incas they were amazed by the tremendous amounts of gold. For Incas gold was a sacred metal, the Sun God's metal, and colossal amounts of gold had accumulated in the temples. When the Spaniards took Atahualpa, the Great Inca, prisoner, they promised him freedom for a fantastic ransom of almost 50 cu.m. of gold. But Francisco Pizarro thought it dangerous to free the Great Inca and, without waiting for the ransom, the Spaniards executed Atahualpa. When the Incas learned about the death of their leader, the caravan consisting of 1100 llamas carrying gold had already been on its way. Incas hid the gold in the mountains of Azangaro ("the remotest place"). But they could not hide all their treasures. Spaniards captured and looted Cuzco, one of Peru's richest cities. They melted the priceless creations of ancient craftsmen into gold ingots and sent them to Spain.

In Russia mining of gold began in 1600 but it was not until the 19th century that the large scale extraction of this metal started.

The Latin name for gold, aurum, originates from the word Aurora (dawn).

Relative sizes of an 860 kg block of gold ore, and the 30 g of gold that can be extracted from it.

Gold jewelry consumption by country in tonnes

Source - Chemical Elements : How They Were Discovered

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Uranus smells like rotten eggs

TAKE A WHIFF  Uranus is a lovely robin’s egg blue in this image taken by the Voyager 2 spacecraft when it flew past in 1986. New measurements of the planet’s chemistry suggests it may smell like eggs, too — that is, really rotten eggs. 

Uranus’ upper clouds are made of hydrogen sulfide — the same molecule that gives rotten eggs their noxious odor.

Using a spectrograph on the Gemini North telescope in Hawaii, planetary scientist Leigh Fletcher and his colleagues detected the chemical fingerprint of hydrogen sulfide at the top of the planet’s clouds. This isn't a complete surprise: Observations from the 1990s showed hints of hydrogen sulfide lurking deeper in Uranus’ atmosphere. But the gas hadn’t been conclusively detected before.

The clouds aren’t just smelly — they can help nail down details of the early solar system. Uranus’ hydrogen sulfide clouds set it apart from the gas giant planets, Jupiter and Saturn, whose cloud tops are mostly ammonia.

Hydrogen sulfide freezes at colder temperatures than ammonia. So it’s more likely that frozen hydrogen sulfide ice crystals would have been abundant in the further reaches of the early solar system, where the crystals could have glommed onto newly forming planets. That suggests that ice giants Uranus and Neptune were born farther from the sun than Jupiter and Saturn.

Fletcher is far from repelled by the malodorous clouds. He and other planetary scientists want to send a spacecraft to the ice giants — the first since the Voyager spacecraft visited in the 1980s — to find out more.

Source - ScienceNews

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Citations - P. Irwin et al. Detection of hydrogen sulfide above the clouds in Uranus’s atmosphere. Nature Astronomy. Published online April 23, 2018. doi: 10.1038/s41550-018-0432-1.