Section lemons, remove seeds, and chop pulp. Set aside. Combine rind, baking soda, and water in a saucepan. Cook, over medium high heat, until mixture boils, stirring frequently. Add sugar and reserved fruit, stirring well. Cook until mixture reaches a full, rolling boil, stirring occasionally. Boil hard 1 minutes. Remove from heat; stir in pectin. Skim foam. Let stand for 5 minutes, stirring occasionally to distribute fruit.
Pour into hot jars, leaving 1/4 inch (6 mm) head space. Adjust caps.
Process 10 minutes in boiling water bath.