Gold and Silver Metallurgy

Knowing composition of Gold and Silver is very important if you wish to have knowledge about Jewellery.

Gold
Atomic No.   = 79
Atomic Symbol = Au

Atomic Mass = 197 amu

Melting point = 1060° C

24K Gold      = 100%
22K Gold      =  91.6%
20K Gold      =  83.3%
18K Gold      = 75%
14K Gold      = 58.3%
 8K Gold       = 34%
 9K  Gold      = 20% Ag + 10%Zn + 30%Cu(Zn lightens the colour to pale yellow)
             Or
                     = 10%Ag + 20%Zn + 40%Cu + 30% Au (Cu makes the colour darker)
Types of Gold
Pink Gold       =  75% Gold  :  25% Cu
Green Gold    =  75% Gold  :  25%
Blue Gold      =  75% Gold  :  25% Fe
Hardness increases, Melting pt.
White Gold    =  75% Gold  :  25% Pd(Palladium)
Earlier Zn and Ag were used but now Pd is used because it gives a better finish. Nickel was also used  in white Gold but it develops allergy



Alloy = W(K1 – K2) / K2

W = Weight of gold
K1 = Previous caratage
K2 = Wanted caratage



Silver
Atomic No.   = 47
Atomic Symbol = Ag

Atomic Mass = 107 amu

Melting point = 960° C
 

Borax       : Sodium tetraorate (Na2B4O7)    (Flux)
Nitric Acid : ( HNO3) ( Purification of gold)
Sulphuric Acid  : (H2SO4) ( Cleaning of Ag, Au, Cu)
Hydrochloric Acid  : (HCl)  ( To dilute Enamel/meena)