Combine egg whites, sugar, salt, water, and corn syrup in a double boiler. Beat 1 minute or until thoroughly mixed
Then place over boiling water and beat constantly at high speed of electric mixer or with a rotary beater for 7 minutes until frosting will stand in stiff peaks. Stir frosting up from bottom and sides of pan occasionally.
Remove from boiling water and pour at once into a large bowl Add vanilla and beat 1 minute until thick enough to spread.
Makes about 4 1/2 cups enough to cover tops and sides of two 8 or 9 inch layers or a 10 inch tube cake.