Platinum coated silver powder

Claim 1

A process for producing a platinum coated silver powder comprising (a) forming a first composition of a slurry comprising of from about 20 to about 30% by weight of a relatively finely divided silver powder relatively uniformly dispersed in said slurry, from about 0.3 to about 0.4% by weight of lignosulfonate and from about 0.7 to about 1.5% by weight of ammonia, balance water, (b) forming a second composition of a slurry comprising from about 5 to about 7.5% by weight of platinum as a platinum-ammonium complex as a solid, relatively uniformly dispersed in a water soluble alkanol, (c) mixing a sufficient ammount of said second compositions with said first composition to achieve a weight ratio of Ag to Pt from about 90:10 to about 95:5, (d) adjusting the pH of said mixture of from about 8 to about 10, (e) adding a sufficient amount of hydrazine to said mixture to achieve a weight ratio of hydrazine to platinum of from about 7 to 5, (f) maintaining the resultant slurry at a temperature of from about 40° C. to about 60° C. for a sufficient time to coat essentially all of said platinum onto said silver and (g) separating the platinum coated silver powder from the remainder of the slurry.