The ethanol was acidified and fatty acids were reextracted
into fresh heptane. Heptane (50 ml) containing
the radioactive compound then was extracted
with an equal volume of 0.01 N H$04 in a separatory
funnel to insure removal of any remaining traces of
water-soluble radioactive impurities, and unlabeled carrier
fatty arid (10-20 peq/ml) was added