Deniges

KUCHEROV - DENIGES Hydration Water addition to a triple bond (Kucherov) or to a double borxl (Oeniges) under mercury salt catalysis... 

Denig s test for citric acid in the saponification liquor is as follows —... 

The only difficulty in obtaining a sharp end point lies in the fact that silver cyanide, precipitated by local excess concentration of silver ion somewhat prior to the equivalence point, is very slow to re-dissolve and the titration is time-consuming. In the Deniges modification, iodide ion (usually as KI, ca 0.01 M) is used as the indicator and aqueous ammonia (ca 0.2M) is introduced to dissolve the silver cyanide. 

The method may also be applied to the analysis of silver halides by dissolution in excess of cyanide solution and back-titration with standard silver nitrate. It can also be utilised indirectly for the determination of several metals, notably nickel, cobalt, and zinc, which form stable stoichiometric complexes with cyanide ion. Thus if a Ni(II) salt in ammoniacal solution is heated with excess of cyanide ion, the [Ni(CN)4]2 ion is formed quantitatively since it is more stable than the [Ag(CN)2] ion, the excess of cyanide may be determined by the Liebig-Deniges method. The metal ion determinations are, however, more conveniently made by titration with EDTA see the following sections. 

Denig [118] has reported that the length and structure of the hydrocarbon chains of AOS may be determined by cleavage of the sulfo groups in presence of excess phosphorus pentoxide and hydrogenation of the hydrocarbons before determining the -alkanes and isoalkanes by pyrolysis gas chromatography. 

R. Denig, Trudy Mezhdunar. Kongr. Poverkhn.-Akt. Veshchestvam, 7th Meeting, Moscow, September 1976, Vol. 1, p. 514. 

The use of basic organic dyes for ion pair extraction-photometric determination has been described.87 After ammonia treatment, an orange-red color with CUS04 and H2O2 (Deniges) can be quantitated.88 A water insoluble violet complex (X max. 620 nm) with 2-picoline-Cu(II) has also been reported.89... 

Truog, E. and Meyer, A.H. (1929) Improvements in the Deniges colorimetric method for phosphorus and arsenic. Industrial and Engineering Chemistry, Analytical Edition, 1, 135-139. 

Reppmann, Zeitsch. anal. Chem., 1934, 99, 180. For other colorimetric methods, see Delaville and Belin, Bull. 80c. Chim. biol., 1927, 9, 91 Deniges, ibid., 1927, 9, 343 Reith, Pharm. Weekblad, 1933, 70, 369 Quincke and Schnetka, Z. Vnters. Lebensm., 1933, 66, 581 Taubmann, Arch. exp. Path. Pharm., 1934, 176, 751. 

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. 

Refs 1) J.A. Sanchez, "Life and Work of Prof Georges Deniges , Rev Asoc Bioquim Argentina... 

---