text: *For biodiesel fuel: waste vegetable oil (WVO) must be neutralized before a batch may be processed.  A portion of WVO is titrated with a base to determine acidity, so the rest of the batch may be neutralized properly.  This removes free fatty acids from the WVO that would normally react to make soap instead of biodiesel fuel.
  *Kjeldahl method: a measure of nitrogen content in a sample. Organic nitrogen is digested into ammonia with sulfuric acid and potassium sulfate.  Finally, ammonia is back titrated with boric acid and then sodium carbonate.
  *Acid value: the mass in milligrams of potassium hydroxide (KOH) required to titrate fully an acid in one gram of sample. An example is the determination of free fatty acid content.
  *Saponification value: the mass in milligrams of KOH required to saponify a fatty acid in one gram of sample. Saponification is used to determine average chain length of fatty acids in fat.
  *Ester value (or ester index): a calculated index. Ester value = Saponification value – Acid value.
  *Amine value: the mass in milligrams of KOH equal to the amine content in one gram of sample.
  *Hydroxyl value: the mass in milligrams of KOH corresponding to hydroxyl groups in one gram of sample. The analyte is acetylated using acetic anhydride then titrated with KOH.