Slowly boil syrup, sugar and 1 cup of the water together for 10 minutes.
Sprinkle gelatin over remaining cold water and let stand for 5 minutes.
Add softened gelatin to the hot syrup and stir until completely dissolved.
Cool and add the juices and salt.
Pour into freezing tray of a mechanical refrigerator, set at coldest temperature and freeze.
When the mixture becomes mushy, loosen from the sides of the pan, remove to a chilled bowl and beat hard with a rotary egg beater for a few seconds, then add stiffly beaten egg whites and again beat hard until well blended.
Return immediately to the freezing compartment to finish freezing.