IMOS Module 6 - Gold & Silver

UF IDS2935: Impacts of Material Science Module 6

Properties of Gold

• color: gold, butter yellow

• hardness: 2-3

• element name: Au

• very dense: gold m³ = 19,300 kg

• most ductile

• most malleable

• can be optically transparent

• does not oxidize

• does not combine/react with other elements often

• does not react with acids

• good electrical conductor

Properties of Silver

• color: silver-white

• hardness: 2.5-3

• very malleable

• very ductile

• oxidizes (changes color)

• naturally occurring as chloride or sulfide

• good electrical conductor

• good thermal conductor

• most lustrous metal

Gold v. Silver Properties

• soft

• conductive

• currency metals

• weak metallic bonds

• extra electron

Method of Extraction

1. amalgamation

2. cyanidation

3. liquidation

4. slucing

5. Cupellation

6. Parting

Amalgamation

extracting gold from the rock by 1) dissolving crushed gold ore with mercury 2) boiling off mercury

Cyanidation

• extracting gold rocks by dissolving gold in cyanide solution

• high percentage of gold extraction

• potentially toxic

Liquidation

extracting gold and silver from copper by 1) mixing with leab 2) heating until lead melts 3) pour off lead 4) following with cupellation

Slucing

extracting gold from graving using gravity (think sifting during goldrush)

Cupellation

extracting silver from lead by 1) heating lead sulfide 2) lead oxidizies at 960C 3) silver is left behind

• 1 ton of lead = 1 lb of silver

• toxic lead pollutes waterways

Parting

separating gold and silver from each other by 1) heating with salt 2) forms silver chloride 3) turn into silver

Ancient History of Gold (40,000 BC-50 BC)

• used in Egypt for burials

• first coins are made in Asia Minor

• Alexander the Great leads the largest military campaign sponsored by gold

• Greeks and Jews in Alexandria practiced alchemy

• Julius Caesar bring back gold from Gaul to repay Rome’s debts

Modern History of Gold (700 AD-1899 AD)

• Gold is discovered in Brazil and becomes the largest producer

• 17 lb nugget is found in North Carolina

• the first goldrush sparked in North Carolina

• California Goldrush is triggered and hastens Western settlement

• Gold is discovered in New South Wales, AUS

• USS Central America sinks 30,000 lbs of gold near North Carolina coast

• Gold and silver found in Nevada

• Gold is found in South Africa and has become the majority of mining

• Gold is discovered in salmon river and created the Klondike Goldrush

Contemporary History of Gold (1900-Present)

• Engelhard Corp. introduces a way to print gold on surfaces

• Niels Bohr, Mac Von Laue, and James Frank make discoveries using gold

• George de Hevesy dissolved Nobel Prizes to hide from Nazis

• USS Central America is discovered (only 20% of gold is recovered)

• total Gold discovered = 187,000 tons = all from metors

Modern Uses of Gold

• currency standard until WWII

• used in jewlery and awards

• usefil in microelectronic industry

• used for decorative purposes

• used for red coloring in glass

• used as reflector (space face shields)

• used in cockpits

Modern Uses of Silver

• used in decorative arts

• used in photography and photographic firm

• used as a conductor of electricity and heat

• used for coins (90% of coin)

• used for jewelry and silverware

Reasons to Use Alloys

• keeps costs down

• makes gold stronger

• changes color

Karat System

• 24 kt = 100% (very soft)

• 18 kt = 75%

• 14 kt = 58%

• 12 kt = 50%

• 10 kt = 42%

• <10 kt = not gold in US

Intrisic v. Extrinisc Value

• Intrinsic: naturally occurring value

• Extrinsic: value deemed by society (use in technology, medicine, electronics)

Money v. Currency v. Coins

• money: medium of exchange

• currency: a form of money guaranteed by a territory or government

• coins: a form of money and currency

Roles of Money

1. medium of exchange

2. standard of value (comparison of goods)

3. way of storing value

4. means of payment

Characteristics of Money

1. durability

2. divisibility

3. portability

4. homogeneity

5. acceptability

6. limited/stable supply

History of Gold/Silver as Money

• precious metals described as wealth in the Old Testament

• first record in cuneiform tablet

• first form as hack-silver

• first datable coins from Ephesus (electrum coins = less gold = scam)

• Ancient Egypt: kites of silver

• Ancient Greek: drachma and electrum coin

• India: silver-punched coin

• China: knife money and bronze spade-shaped coin

Nanotech Size

1 billionth of a meter

Modern Uses of Nanoparticles

• cars

• iPod

• computers

• washing machines

• clothing

Nanoparticles and Interaction with Light

• small size changes color and interaction with light

• 25 nm = red

• 50 nm = green

• 100 nm = orange

Pasmon Resonance

changing the size of particles changes how they interact with sound

Gold Nanoparticles

• gold core and silica shell

• absorb light in infared wavelengths

• used in thermal ablation of tissue

• tissue absorption is minimal

• penetration is optimal

Uses for Nanomaterials in Medicine

• drug delivery

• chemotherapeutics

• hyperthermia

• therapeutic agent

• carrying of imaging agent

• release of drugs

Methods of Formation of Nanomaterials

• colvalent organic sythesis

• self-assembly

• crystal formatino

• laser ablation

• grinding

• milling

• fabrication