Place rhubarb, pineapple and sugar in a large kettle; stir to blend well. Place over high heat until it boils. Reduce heat and boil hard for 20 minutes. Stir in jello until dissolved. Remove from heat and skim carefully. Pour into sterilized jars and seal with paraffin. Adjust covers when paraffin has set, wipe outside of jars and store in cool, dry place. This can be used with frozen, unsweetened rhubarb.