Pure yellow gold, fine gold, is softer than pure silver, but harder than tin. Its beauty and sheen are unmatched by ay alloyed gold. Because of the softness of pure gold it is practically useless for jewelry applications.
By adding alloying elements to gold it increases the toughness and the hardness of the metal. Almost any metal can be melted with gold, but only certain metals will not noticeably change the color or make the metal brittle. The addition of the metal Indium turns gold into a purple color, mixing copper causes a visual reddening effect, adding silver causes a visual greening effect and adding nickel or palladium causes a visual whitening effect.
To produce 18 karat and 14 karat yellow gold, jewelers add copper, silver and zinc to gold and to produce 18 karat and 14-karat white gold, they add copper, nickel and zinc. By adjusting the proportions of these coloring metal agents it causes the array of colors on the market.
Therefore, the difference between yellow gold and white gold is simple. Yellow gold is alloyed with silver and white gold is alloyed with nickel.
Resources:
WWW.MOYENCO.COM
WWW.THEPRINCESSJEWELERS.COM
WWW.NATIONALJEWELERANSCHAR.COM