In a medium saucepan heat and stir the water and sugar over medium heat until sugar is dissolved. Remove from heat; cool.
Meanwhile, place the raspberries in a blender container or food processor bowl. Cover and blend or process until pureed. Sieve puree; discard seeds. (Should have about 1-1/2 cups puree.) Stir puree and lemon juice into sugar mixture. Cover and chill for 4 to 24 hours.
To serve, stir club soda into raspberry mixture. Serve over ice. Makes 8 to 10 servings.