Deniges reaction

Although coordination compounds have sometimes been used as titrants, e.g. ferrocyanide ions for the titration of zinc(II), and permanganate or dichromate ions in redox titrations, probably the only outstanding reaction in classical titrimetry that involves the reversible formation of a coordination compound is the Liebig-Deniges reaction. 

Tertiary hydroxyl the Deniges reaction, a yellow or reddish precipitate with HgS04 + -1-... 

Wagenaar M (1926) The Deniges reaction for citric acid. Pharm Weekblad 63 1293-1299... 

Deniges, G., Reaction de coloration extremement sensible des phosphates et arseniates. Ses applications, Comptes Rendus de I Academie des Sciences 171, 802, 1920. 

Therefore, these reactions constitute a means to distinguish both sorts of barbiturs. This result must be connected to Denigds reaction used in analytical toxicology in order to search for barbiturics extracted in acidic medium. Deniges reagent is mercuric sulfate in a mixture of sulfuric and acetic acids ... 

The excess of cyanide ions is titrated with a standard silver nitrate solution according to a principle close to that prevailing in Liebig-Deniges method. If a small quantity of silver iodide is added to the initial ammonia solution containing Ni + ions, the turbidity it induces because of its insolubility disappears after an addition of cyanide ions because of the occurrence of the reaction... 

Similarly as with the Deniges method, Stahr was not the first and this reaction was performed marty years before by French organic chemist Auguste Andre Thomas Cahours (1813-1891). In 1847 he published paper entitled Relatives a Taction du... 

Spindler O (1905) New modification of the reaction of Denige s. Proof of tartaric acid in citric acid. Chem Ztg 28 15-13... 

Denig used a pyrolysis gas chromatograph to perform the Hofmann elimination reaction (19). The quaternary amine is mixed with solid 50 50 KOH/NaOH and heated at 300 C, with the amine and olefin fragments swept into the GC column. 

---