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Gold

In this section you can find a short digression about gold

Gold as “refuge”

Gold
sometimes is part of a defensive financial investment (reassuring good to protect the capital) due to the long stability of his commercial value and his essential non-correlation compared to the stock and bond market trend. Due to his stability the speculation of gold becomes particularly desirable when the trust in currency is less and when the value of currency is exposed to hyperinflaction. The price of gold is also the basis of futures to which we inquire into his supposed future value.

The value of gold is strongly influenced by offer, that’s why its extraction is carefully weighted: increasing the production means make the price collapse.

  Gold carats In the gold alloys, the term carat is indicated as a proportional unit of measure related to purity which quantify the golden parts in an alloy in a basis of 24/24. The “carat” in gold alloys means just one part of gold on a total of 24 metal parts which form the alloy.

So the word 18 carats indicates that the alloy is composed by 18 parts of pure gold and 6 parts of other metals, it is so shortened with the abbreviations ct or kt or more usually only with k and a number immediately after withoud any spaces between the two, for instance 18k.

The maximum pure gold is definely the one of 24 carats (24 parts of pure gold on a total of 24) and we indicate it with 24k.  
  • 9 ct ( 333 parts of gold out of 1000 )
  • 12 ct ( 500 parts of gold out of 1000 )
  • 14 ct ( 585 parts of gold out of 1000 )
Several nations utilized 9 carats up to 14 to produce jewelry for example the ones which comes from America to Germany.  
  • 18 ct ( 750 parts of gold out of 1000 )
They are the most used in Italy especially by factories and gold artisan to produce jewelry.  
  • 22 ct ( 916 parts of gold out of 1000 )
They are used to produce coins as pound, marenghi and so on.  
  • 24 ct ( 999 parts of gold out of 1000 )
They are used to produce bars and several coins.    
  • There is frequently a stamp which represents the signature of the artisan who made the object. This stamp represents the laboratory identification in which this object has been created. (Ex. 1-AR type, I.E. Arezzo – factory number 1 or 45-VI, laboratory number 45 in Vicenza). Most countries want their pure gold jewels to have a warranty mark. This means that when the object is produced, it receives an official stamp which indicates the kind of gold used to produce the object. Normally the stamp is located in a hidden point as the internal part of a ring or in the back of the closing of a bracelet.
 
Gold Alloys
Ternary phase diagram which represents the colors assumed by the alloys Ag-Au-Cu. The digital scales written on the sides of the triangle refer to the percentages of weight of each alloy.  

Jewelry gold:
i.e. the one who is composed by a lot of metals to increase the stiffness, the colour is white or red depending on the kind of alloy (with silver or copper),

Yellow gold:
It is composed by 75% of gold, 12.5% of silver, 12.5% of copper.

Pink gold:
It is generally composed by 75% of gold, 5% of silver, 20% of copper.

Grey gold:
It is composed by 75% of gold, 15% of silver, 10% of copper.

Blue gold: It is a gold and iron alloy. A thermic tratement oxidizes the iron atoms on the gold surface giving it the blue colour.

White gold:
It is made by 75% gold, 25% of nichel, silver or palladium. We can notice that the word “white gold” is often utilized to designate the grey gold. The white gold is covered by a thin coating of rhodium which will disappear because of wear and tear with the passing of time, giving back to the gold a yellow colour. It is an alloy invented after the first world war. For the gilding through thin sheets of gold, the league must be as malleable and ductile as possible.

The gilding gold is composed bt 98,0% of gold, 1,0% of silver and 1,0% of copper. It could even be pure.

The plating red gold
is composed by 94,5% of gold and 5.5% of copper.

The half gilding gold
is composed by 91.5% of gold, 6.0% of silver, 2.5% of copper.

The lemon gilding gold
is composed by 94.5% of gold, 5.5% of silver.

The french gilding gold
is composed by 20% of gold, 80% of silver, in eaurope 50% of gold and 50% of silver.  

Gold and its use in different sectors

The pure gold is too soft to be worked normally; it is hardening by tying it with other metals (normally copper and silver). Gold and its alloys are used to coin coins and they are a standard of currency exchange for many nations. Due to its resistance to corrosion and its large electrical properties it is largely used in industrial applications. They are doing some studies about the use of gold as catalyst, as a matter of fact gold has a big catalytic activity when it looks like nanoparticles released through appropirate supports.

The gold supported catalysts play a fundamental role in different reactions including: Oxidation of carbon monoxid (CO), complete oxidation of hydrocarbons, selective oxidations, water-gas shift reaction. The activity of these catalysts greatly depends on the method of preparation and on the type of support utilized.  

Among other uses:  
  • Electronic components: it unwinds critical functions in many computers, equipments for telecommunications, jet engines and many other industrial applications; they can be used as coating material on electric surfaces to ensure the resistance to corrosion in time.
  • Within astronautical: gold is uesd as a protective coating of many ariticial satellites thanks to his capacity to reflect either the visible light or the infrared one.
  • Medical and diagnostic use: The colloidal gold is used in a certain type of electrophoresi, a method of medical diagnostics. Assembly of dental fillings or bridges, in colloidal suspension it is used to paint ceramics and it is being studied for biological and medical applications. The disodium aurothiomalate is a drug for the treatment of rheumatoid arthritis: the radioactive isotopes 198Au is used in some cancer therapies.
  • Investigations at the microscope: gold is used to cover biological samples to be observed in a scanning electron microscope.
  • In photography: The hydrochloric acid is used in photography to turn the image produced by silver salts.
  • Ornamental purposes: Gold can be modified and become as a thread inserted in tissues and adornments; the white gold – an alloy with platinum, palladium, nickel and zinc is used as a substitute of platinum for several applications even in jewelleries – moreover this league has a low coefficient of thermal expansion; the green gold (combined with silver) and the red gold (combined with copper) are used in the jewelleries.
  • In sport events and prize-givings: the gold medal is the prize given to the winner in many competitions, for instance olympic games and nobel prize.
  • In the cookery: Gold is used as ingredient in some cooking recipes; as it doesn’t have any reactivity it deasn’t adulterate!!!