Addition of large amounts of platinum to a casting gold alloy will:

Platinum It increases strength and corrosion resistance. It also increases melting point and has a whitening effect on the alloy. It helps to reduce the grain size. The transformation between vapor, liquid, and solid is called the change of state. A change from the solid to the liquid state will require additional energy—kinetic energy—to break loose from the force of attraction. This additional energy is called the latent heat of fusion. The temperature at which this change occurs is known as the melting temperature or fusion temperature. Mannapalli 3 ed page 274; Phillips 12th ed page 18