Soften the gelatin in one quarter cup of the water.
Boil together for two minutes the remaining cup water, sugar, syrup, mint and lemon rind.
Add the gelatin and cool to room temperature.
Add the milk, pineapple and lemon juices.
Color a light green and freeze in a two-quart metal pan.
Beat the egg whites.
Break up the frozen mixture, turn it into a mixer or other bowl and beat until very fluffy and soft but not melted.
Fold in the egg whites.
Return to the pan and freeze until firm.