Place apricots in a large mixing bowl with water to cover; soak overnight.
Lightly scrape outer skins of oranges and grapefruit with blade of a knife to release citrus oils. Peel oranges and grapefruit; chop rind (reserve pulp for other uses).
Combine chopped rind, 2 quarts water, and soda in a large stainless steel saucepan; bring to a boil. Reduce heat; cover and simmer 15 minutes. Rinse well; drain.
Add remaining water to rind mixture in saucepan; bring to a boil. Reduce heat; cover and simmer 15 minutes. Remove from heat. Keep covered, and let rind stand in cooking liquid overnight. Drain well.
Drain and mince apricots. Place in a flat-bottomed kettle. Add crushed pineapple, lemon juice, sugar, and orange and grapefruit rind, stirring well. Slowly bring to a boil, stirring until sugar dissolves. Boil, stirring constantly, until mixture registers 220° on a candy thermometer or until mixture sheets from a cold metal spoon. Remove from heat, and skim off foam with a metal spoon.
Quickly ladle marmalade into hot sterilized jars, leaving 1/4- inch headspace. Cover at once with metal lids, and screw bands tight. Process marmalade in boiling-water bath 10 minutes.