In a saucepan combine the sugar, the rind, and 2 cups water, bring the mixture to a boil, stirring until the sugar is dissolved, and simmer the syrup for 5 minutes.
Let the syrup cool, strain it into a bowl, and stir in the lemon juice. Chill the syrup, covered, for 2 hours, or until it is cold.
(The syrup may be made up to one day in advance and kept covered and chilled.) Freeze the syrup in an ice cream freezer according to the manufacturer's instructions until it is almost frozen but still mushy.
In a bowl beat the egg white until it holds soft peaks, add it to the sherbet, and freeze the sherbet again in the ice-cream freezer until it is frozen but not firm.
Remove the dasher and freeze the sherbet, covered, until it is firm.
(The sherbet may be made up to 3 days in advance and kept covered tightly and frozen.) Yield: 1 quart