Unit Definition (once [France]) The onça, once, oncia, onza is traditional names for the ounce unit in Romance languages. The French once equals 1/16 livre or about 30.59 grams (1.079 ounce).
Unit Definition (picogram) The picogram is a metric unit of mass equal to 10E-12 gram or one millionth of a microgram.
Weight/Mass 
