In a large stainless steel saucepan, combine apricots and water. Bring to a boil over medium-high heat. Reduce heat and boil gently, stirring occasionally, until apricots are soft, about 20 minutes.
Working in batches, transfer apricot mixture to a food mill or food processor fitted with a metal blade and puree just until a uniform texture is achieved. Do not liquify. Measure 6 cups of apricot puree.
In a clean large stainless steel saucepan, combine apricot puree and sugar. Stir until sugar dissolves. Bring to a boil over medium-high heat, stirring frequently. Reduce heat and boil gently, stirring frequently, until mixture thickens and holds its shape on a spoon.
Prepare canner, jars and lids.
Ladle hot butter into hot jars, leaving 1/4 inch headspace. Remove air bubbles, wipe rim and place lids.
Place jars in canner, ensuring they are completely covered with water. Bring to boil and process for 10 minutes. Remove canner lid. Wait 5 minutes then remove jars, cool and store.