Boil the water, corn syrup and sugar until the mixture thickens and forms a firm ball when dropped into cold water, or spins a thread when dropped from a spoon. Add the salt to the egg whites and whip until stiff but not dry. Pour the hot syrup into the eggs in a very fine stream, constantly beating the whites. After the syrup is absorbed, continue beating until it is the right consistency for spreading. Add the orange juice to keep icing from becoming gritty and beat in vanilla.