Cut the lemon from top to bottom into quarters. Remove the fruit from each quarter, remove any seeds, and reserve the fruit.

Use a spoon to remove as much white pith of the peel as possible. Discard the pith.

Slice the lemon peel crosswise into strips no greater than ⅛ inch wide.

Peel the tangerines and remove any seeds that you may find in the fruit. The tangerine peel is very thin so that you do not have to remove any of the pith. Slice the tangerine peel crosswise just like you did with the lemon peel, no greater than ⅛ inch wide.

Combine the lemon and tangerine peels and measure. There should be 1 1/2 to 2 cups of sliced peels. Place them in a 3 to 4 quart pot. Add the 2½ cups water and ⅛ teaspoon baking soda. Cover, bring to a boil, and simmer gently for 20 minutes.

While the sliced peel is simmering, combine the lemon and tangerine fruit in a blender.

Run the blender at a low speed for a about 1 minute. There should be about 2 cups of blended fruit when done.

Add the blended fruit to the rind in the pot when it is done simmering.

Return to a boil and simmer gently, uncovered, for 10 more minutes. Measure the fruit in the pot. There should be 4 cups. If there is too much, then remove some of the liquid or continue to cook down until reduced to 4 cups. If there is not enough, then add some water to make up the difference. Stir the Original Sure-Jell powdered fruit pectin into the fruit and bring to a full boil while stirring frequently.

Add the 5 1/2 cups sugar and continue to stir until all of the sugar is dissolved.

Return to a hard boil for 1 minute.

Remove from heat, skim foam, pour into hot sterilized jars, and seal.

Process the tangerine marmalade for 10 minutes in a boiling water bath. Remove the jars from the pot and place on a dry towel to cool. Finally, gently shake the jars after 1 hour and 2 hours, to prevent all of the rind from floating to the top.