Wash the lemons in hot water and dry them with a towel. Peel the sheet quite thin and cut into fine strips. Squeeze lemons and grapes cut in two halves. Boil juice and fruit and leave covered to soak 10-15 minutes. Stretch strainer over a bowl of cheesecloth, pour it over the fruit mass and wring it out. Chilled fruit juice, citric acid, sugar and lemon peel put in a large saucepan. Cook them at constant stirring, skim. When the jelly gets ready pour into jars and pleads with the caps down.