Prepare boiling water canner. Heat jars and lids in simmering water until ready for use. Do not boil. Set bands aside.
Remove peel from oranges and lemons. Scrape off 1/2 of white pith and discard. Thinly slice peel and place in baking soda and water in a 6 or-8-quart saucepan. Cook 20 minutes, covered. Remove membrane from fruit pulp. Chop fruit, reserving juice. Add fruit and juice to peel mixture. Simmer 10 minutes, covered.
Combine prepared with lemon juice and sugar in a 6 or 8-quart saucepan. Add up to 1/2 tsp. butter or margarine to reduce foaming, if desired. Bring mixture to a full rolling boil that cannot be stirred down, over high heat, stirring frequently.
Add pectin, immediately squeezing entire contents from pouch. Continue hard boil for 1 minute, stirring constantly. Remove from heat. Skim foam if necessary.
Ladle hot jam into hot jars leaving 1/4 inch headspace. Wipe rim. Center lid on jar. Apply band until fit is fingertip tight.
Process jars in a boiling water canner for 10 minutes, adjusting for altitude. Remove jars and cool. Check lids for seal after 24 hours. Lid should not flex up and down when center is pressed.
STRAWBERRY LEMON MARMALADE: Prepare as above, except omit oranges. Reduce water to 1/2 cup. Crush 5 cups fresh hulled strawberries; measure 3 cups crushed strawberries. Stir into mixture with the lemon sections.