<P> Some examples of primary standards according to the European Pharmacopoeia 5, ch . 4.2: </P> <Ul> <Li> Arsenic trioxide for making sodium arsenite solution for standardisation of sodium periodate solution (until Ph . Eur. 3, Appendix 2001 also for iodine and cerium (IV) sulfate solutions, since Ph . Eur. 4, 2002 standardised by sodium thiosulfate) </Li> <Li> Benzoic acid for standardisation of waterless basic solutions: ethanolic sodium and potassium hydroxide, TBAH, and alkali methanolates in methanol, isopropanol, or DMF </Li> <Li> Potassium bromate (KBrO) for standardisation of sodium thiosulfate solutions </Li> <Li> Potassium hydrogen phthalate (usually called KHP) for standardisation of aqueous base and perchloric acid in acetic acid solutions </Li> <Li> Sodium carbonate for standardisation of aqueous acids: hydrochloric, sulfuric acid and nitric acid solutions (but not acetic acid) </Li> <Li> Sodium chloride for standardisation of silver nitrate solutions </Li> <Li> Sulfanilic acid for standardisation of sodium nitrite solutions </Li> <Li> Zinc powder, after being dissolved in sulfuric or hydrochloric acid, for standardization of EDTA solutions </Li> </Ul> <Li> Arsenic trioxide for making sodium arsenite solution for standardisation of sodium periodate solution (until Ph . Eur. 3, Appendix 2001 also for iodine and cerium (IV) sulfate solutions, since Ph . Eur. 4, 2002 standardised by sodium thiosulfate) </Li> <Li> Benzoic acid for standardisation of waterless basic solutions: ethanolic sodium and potassium hydroxide, TBAH, and alkali methanolates in methanol, isopropanol, or DMF </Li>

What is a primary standard in volumetric analysis