Oxidations with potassium permanganate in the presence of fluoride

Summary The titration of ferrous iron in presence of fluoride ions in acid medium gives fleeting end points and erroneous results. A method is deviced to overcome this difficulty by oxidising the ferrous with an excess of KMnO₄ in alkaline medium. After mixing the reactants the excess of KMnO₄ is reduced by an excess of Hg₂ ²⁺ ions in presence of H₂SO₄ and fluoride. The remaining mercurous is then titrated with standard KMnO₄ solution.Part III: Issa, I. M., and M. Hamdy: Z. analyt. Chem. 174, 418 (1960).     

Oxidations with potassium permanganate in the presence of fluoride

Summary Quadrivalent selenium can be determined with fair accuracy by mixing with an excess of KMnO₄ in the presence of 25–75 ml of 2% NaF solution and 4–7 ml of 9 N sulfuric acid. After leaving the reaction mixture for 10–30 minutes the excess KMnO₄ is estimated by one of the following procedures: A) Titration of the excess KMnO₄ with monovalent mercury, B) Adding an excess of Hg₂ ²⁺ solution to react with the excess KMnO₄ followed by titrating the excess mercurous with KMnO₄ solution.Part I: Issa, I. M., and M. Hamdy, Z. analyt. Chem. 172, 94 (1980).     

Oxidation with manganate solutions

Summary Manganate solutions prepared by the reduction of permanganate with formic acid in 1 M NaOH are fairly stable in a concentration of 0.015 M in presence of 1 M NaOH. They can be titrated successfuly with arsenite in the presence of telluric acid but not in its absence owing to the sluggishness of the reaction. Titration of arsenite with manganate yields always lower results deviating by 0.77% from the theoretical values in presence of telluric acid and 0.1–0.2 M NaOH. Much earlier end points with errors amounting to – 17 or – 38% are obtained in the absence of telluric acid.This work was started during 1957. Since that time the reactions of manganate with arsenite, tellurite, bivalent manganese and hydrogen peroxide were studied in our laboratory. While this work was prepared for publication den Boef et al. published their first investigation in the same line in 1959.     

Oxidations with potassium permanganate in the presence of fluoride

Summary Trivalent chromium and quadrivalent vanadium can be determined with fair accuracy by a method consisting in mixing either with an excess of KMnO₄ in the presence of 0.3 to 1.8 M alkali hydroxide. After leaving the mixture for 5 min, the solution is acidified with sulphuric acid and mixed with 50 to 75 ml of 2% NaF solution. An excess of monovalent mercury Hg₂ ²⁺ solution is then added, the solution heated to 40° C and then titrated with KMnO₄ solution in the presence of Cu²⁺ ions to conceal the pink manganic fluoride colour.Part II: Issa, I. M., and M. Hamdy: Z. analyt. Chem. 172, 162 (1960).     

Determination of the stability constant and thermodynamic parameters between Tl<Superscript>+</Superscript>, Ag<Superscript>+</Superscript> and Pb<Superscript>2+</Superscript> cations with 2,6-di(furyl-2yl)-4-(4-methoxy phenyl)pyridine as a new synthesis ligand

The complexation reaction between Tl⁺, Ag⁺ and Pb²⁺ cations with 2,6-di(furyl-2yl)-4-(4-methoxy phenyl)pyridine as a new synthesis ligand in acetonitrile (ACN)–H₂O and methanol (MeOH)–H₂O binary solutions has been studied at different temperatures using conductometric method. The conductometric data show that the stoichiometry of the complexes is 1: 1 [M: L] and the stability constant of complexes changes with the binary solutions identity. Also, the structure of the resulting 1: 1 complexes was optimized using the LanL2dz basis set at the B3LYP level of theory using GAUSSIAN03 software. The results show that the change of logK_f for (DFMP.Pb)²⁺ and (DFMP.Ag)⁺ complexes with the mole ratio of acetonitrile and for (DFMP.Ag)⁺ and (DFMP.Tl)⁺ complexes with the mole ratio of methanol have a linear behavior, while the change of logK_f of (DFMP.Tl)⁺complex in ACN–H₂O binary solutions (with a minimum in X_ACN = 0.5) and (DFMP.Ag)⁺ complex in MeOH–H₂O binary solutions (with a minimum in X_MeOH = 0.75) show a non-linear behavior. The selectivity order of DFMP ligand for these cations in mol % CAN = 25 and 75 obtain Tl⁺ > Pb²⁺ > Ag⁺ but in mol % CAN = 50, the selectivity order observe Pb²⁺ > Tl⁺ > Ag⁺. Also, this selectivity sequence of DFMP in MeOH–H₂O (mol % MeOH = 75 and 100) and (mol % MeOH = 50) is obtained Pb²⁺ > Ag⁺ and Tl⁺ > Ag⁺ > Pb²⁺ respectively. The values of thermodynamic parameters show that these values are influenced by the nature and the composition of binary solution. In all cases, the resulting complexes are enthalpy stabilized and entropy destabilized. The TΔS_C^° versus ΔH_C^° plot of all obtained thermodynamic data shows a fairly good linear correlation which indicates the existence of enthalpy-entropy compensation in the complexation reactions.     

Versuche zur Anreicherung von Spurenelementen durch Ausf?llen des Hauptbestandteils

Zusammenfassung Am Beispiel von Silberhalogenidfällungen werden Möglichkeiten aufgezeigt, die adsorptive Mitfällung von Spurenelementen durch Konkurrenzreaktionen zu beeinflussen.Entgegen älteren Literaturangaben wurde eine Verringerung der Spurenadsorption durch Aciditätserhöhung bis zu 7 M salpetersauren Lösungen nicht beobachtet.Die von Silberhalogenid-Niederschlägen in Gegenwart überschüssigen Halogenids normalerweise weitgehend adsorbierten Kationenspuren Bi³⁺, Cd²⁺, Hg⁺, Pb²⁺, Pd²⁺, Tl⁺ und Tl³⁺ werden dann nicht mitgefällt, wenn sie bei der Matrixfällung in genügend stabile undissoziierte Moleküle oder in Komplexanionen übergeführt werden. Als Komplexbildner wirkt bei Cd²⁺, Hg²⁺, Pd²⁺, Tl⁺ und Tl³⁺ schon das im Überschuß vorhandene Bromid, während überschüssiges Jodid die Elemente Bi³⁺, Cd²⁺, Hg²⁺ und Pd²⁺ komplexiert. Mit Ausnahme von Tl⁺ können alle diese Ionen in neutraler Lösung auch mit ÄDTA maskiert und in Lösung gehalten werden, wobei die bekannte pH-Funktion der Komplexbildungskonstanten eine gezielte Selektivierung der Spurenanreicherung möglich macht. Solange die Probelösung bei der Fällungsreaktion noch Silber im Überschuß enthält, werden die ÄDTA-Komplexe zahlreicher Kationen zunächst adsorptiv mitgefällt, nach Überschreiten des Äquivalenzpunktes jedoch wieder desorbiert.Durch Belegen der aktiven Oberfläche der Silberhalogenid-Mederschläge mit stark adsorbierbaren Ionen kann die Mitfällung der übrigen Elemente verhindert werden. Die Untersuchungen ergaben die folgende Reihe in der Stärke der Adsorption von Kationen an AgCl: Tl⁺>Pb²⁺>(Hg²⁺; Pd²⁺)>Tl³⁺>Bi³⁺>Cd²⁺.

---

Enrichment of trace elements by precipitation of the main componentIII. Investigations of the influence on trace adsorption at silver halogenide precipitates

The co-precipitation of trace elements by adsorption can be influenced by competetive reactions. This is demonstrated with silver halogenide precipitations. Opposed to former literature a diminution of trace adsorption by raising the acidity could not be observed up to 7 M solutions of nitric acid. Cation traces as Bi³⁺, Cd²⁺, Hg²⁺, Pb²⁺, Pd²⁺, Tl⁺, and Tl³⁺, which are normally adsorbed by silver halogenide precipitates in presence of surplus halogenids, are not co-precipitated if they are transformed into sufficiently stable undissociated molecules or complex anions.As complexing agent the surplus bromide acts with Cd²⁺, Hg²⁺, Pd²⁺, Tl⁺, and Tl³⁺; the surplus iodide with Bi³⁺, Cd²⁺, Hg²⁺, and Pd²⁺. With the exception of Tl⁺ all of these ions can be masked by EDTE in neutral medium and kept in solution. The known pH-function of the stability constants permits an aimed selection of the elements to be enriched. As long as the solution still contains a silver surplus during the precipitation, the EDTE complexes of numerous cations are co-precipitated at first, however desorbed after exceeding the equivalence point. Depositing of strongly adsorbable ions at the active surface of the silver halogenide precipitates prevents the co-precipitation of other elements. The strength of adsorption at silver chloride is given by the following order of cations: Tl⁺ > Pb²⁺ >(Hg²⁺; Pd²⁺)>Tl³⁺>Bi³⁺>Cd²⁺.

---

---

II. Mitt.: diese Z. 235, 235 (1968).

---

Herrn Professor Dr. E. Asmus zum 60. Geburtstag gewidmet.

---

Wir danken Herrn J. Lohmar für die experimentelle Mitarbeit. Der Fa. E. Merck AG, Darmstadt, sei auch an dieser Stelle für die Überlassung reinsten Silbernitrats gedankt.     

Oxidations with alkaline permanganate using monovalent thallium for the back titration: Estimation of hydrogen peroxide

Owing to the instability of hydrogen peroxide in alkaline solutions, direct oxidation with KmnO₄ did not yield accurate results.The back titration of KmnO₄ in the presence of IN NaOH and Ba⁺² ions also gave inaccurate results. The reaction could not be checked at the manganate state. However, in the presence of 2N NaOH and telluric acid quantitative data were obtained, which is not the case if telluric acid is absent.Another advantageous method is the oxidation of hydrogen peroxide with excess KmnO₄ in the presence of 1N NaOH and telluric acid, followed by back titrating excess oxidant with monovalent thallium.     

Redox and Coordination Behavior of the Hexaphosphabenzene Ligand in [(Cp*Mo)2(μ,η6:η6‐P6)] Towards the “Naked” Cations Cu+, Ag+, and Tl+

Although the cyclo‐P₆ complex [(Cp*Mo)₂(μ,η⁶:η⁶‐P₆)] ( 1 ) was reported 30 years ago, little is known about its chemistry. Herein, we report a high‐yielding synthesis of 1 , the complex 2 , which contains an unprecedented cyclo‐P₁₀ ligand, and the reactivity of 1 towards the “naked” cations Cu⁺, Ag⁺, and Tl⁺. Besides the formation of the single oxidation products 3 a,b which have a bisallylic distorted cyclo‐P₆ middle deck, the [M( 1 )₂]⁺ complexes are described which show distorted square‐planar (M=Cu( 4 a ), Ag( 4 b )) or distorted tetrahedral coordinated (M=Cu( 5 )) M⁺ cations. The choice of solvent enabled control over the reaction outcome for Cu⁺, as proved by powder XRD and supported by DFT calculations. The reaction with Tl⁺ affords a layered two‐dimensional coordination network in the solid state.     

A Thallium Coated Dianion: Trigonal Bipyramidal [F2Al(OR)3]2— Coordinated to Three Tl+ Cations in the Ion Pair [Tl3F2Al(OR)3]+[Al(OR)4]— [R = CH(CF3)2]

The reproducible synthesis of the unusual ionic aluminum compound [Tl₃F₂Al(OR)₃]⁺[Al(OR)₄]^— ( 1 ) is reported. In the reaction of Li[Al(OR)₄] [R = C(H)(CF₃)₂] with TlF the initially desired Tl[Al(OR)₄] only formed with an exact 1:1 stoichiometry, while an excess of TlF led to [Tl₃F₂Al(OR)₃]⁺[Al(OR)₄]^— ( 1 ). Additionally the x‐ray single crystal structure of the byproduct [(R‐OH)TlAl(OR)₃(μ‐F)]₂ ( 2 ) was determined. Compounds 1 and 2 were characterized by X‐ray single crystal structure determinations and 1 also by NMR spectroscopy and an elemental analysis. In 1 the [Tl₃F₂Al(OR)₃]⁺ cation forms a trigonal bipyramid with a pentacoordinate aluminum atom. Three Tl⁺ cations cover the [F₂Al(OR)₃]^2— dianion core and the charge of the resulting [Tl₃F₂Al(OR)₃]⁺ cation is compensated by a weakly coordinating [Al(OR)₄]^— anion. Compound 2 contains a centrosymmetric [Al(OR)₃(μ‐F)]₂^2— dianion core with pentacoordinate aluminum atoms building a distorted edge sharing double trigonal bipyramid. The [Al(OR)₃(μ‐F)]₂^2— dianion coordinates two [Tl(R‐OH)]⁺ cations giving the non charged molecular [(R‐OH)TlAl(OR)₃(μ‐F)]₂ ( 2 ). Based on BP86/SVP (DFT‐) and lattice enthalpy calculations a pathway of the reaction was proposed to rationalize the formation of the [M₃F₂Al(OR)₃]⁺ cation upon reaction of Li[Al(OR)₄] with MF for M = Tl but not for M = Cs (cf. Cs⁺ and Tl⁺ have very similar ionic radii). Using a suitable BorñHaber cycle and in agreement with the experiment, the enthalpies of the reaction of 2 M[Al(OR)₄] with 2 MF giving [M₃F₂Al(OR)₃]⁺[Al(OR)₄]^— and MOR were shown to be favorable for M = Tl by 127 kJ/mol but endothermic for the formation of the hypothetical [Cs₃F₂Al(OR)₃]⁺[Al(OR)₄]^— by 95 kJ/mol. It is suggested that in the reaction leading to 1 initially Tl[Al(OR)₄] is formed, followed by an abstraction of TlOR and Al(OR)₃. The latter very strong Lewis acid reacts subsequently with an excess of TlF yielding 1 .     

Studies with dithizone : Part 26. The interaction of thallium(III) with solutions of dithizone in organic solvents

The strong oxidising capacity of thallium(III) dominates its reaction with solutions of dithizone (H₂Dz) in organic solvents. When carbon tetrachloride is used as solvent, the unstable thallium(III) complex Tl(HDz)³ is found in the organic phase but it very quickly disproportionates to the thallium(I) complex [Tl(HDz)], and bis-1,5-diphenylformazan-3-yl-disulphide. This reaction is notably faster in chloroform, in which thallium(I) dithizonate is the first identifiable product. In contact with an acidic aqueous phase, thallium(I) dithizonate is reverted to regenerate dithizone in the organic phase and Tl⁺ ions appear in the aqueous phase. Organic solutions of the disulphide disproportionate spontaneously by first-order kinetics to give an equimolar mixture of dithizone and the mesoionic compound, 2,3-diphenyl-2,3-dihydrotetrazolium-5-thiolate: this change is much slower in carbon tetrachloride than in the more polar chloroform and is catalysed by both Tl⁺ and Tl³⁺. If thallium(III) is present in excess, the mesoionic compound is the principal oxidation product of the dithizone although a dication may also be formed. The mesoionic compound does not react with thallium(I) but forms a water-soluble 2:1 complex with thallium(III); partition of this complex into the organic phase is uninfluenced by chloride ions. Because of the large number of competing reactions, the composition of the reaction mixture at any stage of the reaction between thallium(III) and dithizone depends on the relative concentrations of the components, the order in which they are brought together, the time elapsed after mixing, the pH of the aqueous phase, and the nature of the organic solvent.     

Successive substitution titration of calcium and magnesium with EGTA using thallium oxide electrode for indication

Summary It is demonstrated that magnesium can be titrated with EGTA in the presence of CaEDTA complex. On the basis of this substitution reaction, calcium and magnesium are successively titrated with EGTA, if an appropriate amount of CaEDTA is added after having reached the end point for calcium. Both end points are indicated amperometrically using a thallium oxide anode. The method has been tested for analysis of tap and mineral water. Larger amounts of manganese(II) render the calcium result too high. Moreover, the indication of both end points is affected by the electrode position of an inactive MnO₂-layer onto the Tl₂O₃-layer. Reducing agents destroy the Tl₂O₃-layer. These interferences can be overcome by addition of an appropriate amount of manganate(VII) to the sample.

---

Sukzessive Substitutionstitration von Calcium und Magnesium mit ÄGTA, indiziert mit der Thalliumoxidelektrode

Zusammenfassung Magnesium kann mit ÄGTA in Gegenwart des CaÄDTA-Komplexes titriert werden. Auf der Grundlage dieser Substitutionstitration können Calcium und Magnesium nacheinander mit ÄGTA titriert werden, wenn nach dem Endpunkt für Calcium eine ausreichende Menge CaÄDTA zugesetzt wird. Beide Endpunkte werden amperometrisch mit Hilfe einer Thalliumoxidelektrode angezeigt. Die Methode wurde an Leitungswasser und Mineralwasser geprüft. Größere Mengen Mangan(II) bewirken zu hohe Calciumwerte. Darüber hinaus wird die Indikation beider Endpunkte dadurch beeinträchtigt, daß sich eine inaktive MnO₂-Schicht auf der Tl₂O₃-Schicht elektrolytisch abscheidet. Reduzierende Stoffe zerstören die Tl₂O₃-Schicht. Diese Störungen können durch Zugabe von Permanganat vermieden werden.

     

Oxidations with alkaline permanganate using monovalent thallium for the back-titration: Estimation of trivalent arsenic

In absence of Ba⁺² ions arsenite reduces KMnO₄ in alkaline medium to MnO₂ without the appearance of an inflection at the manganate state. Reduction could be checked at the manganate in presence of 1N NaOH and Ba⁺² equal to 3 times that equivalent to MnO₄^-2 and arsenate, and when dilute arsenite solutions are applied viz.0.02N In absence of Ba⁺² ions the end-points are attained later than the MnO₂ stage except in 2–3N NaOH. In presence of telluric acid good results are obtained at all alkalinities whence reduction is checked at Mn⁺⁴.As⁺³ could be estimated also by mixing with KMnO₄ either in the presence of Ba⁺² ions + 1N NaOH or in absence of Ba⁺² ions + I.5–3N NaOH and back-titrating the excess oxidant with monovalent thallium.     

Bismuthiol II as an analytical reagent

Summary Lead was estimated as Bismuthiol II complex of composition (C₈H₅N₂S₃)₂Pb by precipitating it from its chloride or nitrate solution in presence of a mineral acid, acetic acid, tartrate or cyanide. The estimation is quantitative up to a maximumph of about 6.5. The lead-Bismuthiol II complex is stable up to about 311° C and the conversion factor is 0.315. The method affords a complete separation of lead from alkalis and alkaline earths, Be²⁺, Mg²⁺, Zn²⁺, Mn²⁺, Co²⁺, Ni²⁺, Fe²⁺, Fe³⁺, Cr³⁺, Al³⁺, rare earths, Ti⁴⁺, Zr⁴⁺, Th⁴⁺, UO₂ ²⁺, Pd²⁺, As³⁺, Sb³⁺, Cl^–, SO₄ ^2–, PO₄ ^3–, AsO₄ ^3–, MoO₄ ^2– and WO₄ ^2–. Among the sulphide group members Ag⁺, Au³⁺, Hg⁺, Hg²⁺, Tl⁺, Tl³⁺, Cd²⁺ and platinum metals, except Pd²⁺, interfere while oxidising agents decompose the excess reagent. Bi³⁺, Cu²⁺ and Sn²⁺, do not interfere up to a maximum limit of 30 mg, 50 mg, and 250 mg respectively.Part I: see Z. analyt. Chem. 154, 262 (1957).     

Solvent extraction of H3O+, NH4+, Ag+, K+, Rb+ and Tl+ into nitrobenzene by using cesium dicarbollylcobaltate in the presence of a hexaarylbenzene-based receptor

From extraction experiments and γ-activity measurements, the extraction constants corresponding to the general equilibrium M⁺(aq) + 1·Cs⁺(nb) \rightleftarrows \rightleftarrows 1·M⁺(nb) + Cs⁺(aq) taking part in the two-phase water–nitrobenzene system (1 = hexaarylbenzene-based receptor; M⁺ = H₃O⁺, NH₄ ⁺, Ag⁺, K⁺, Rb⁺, Tl⁺; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML⁺ complex species in nitrobenzene saturated with water were calculated; they were found to increase in the series of Rb⁺ < K⁺ < Ag⁺, Tl⁺ < H₃O⁺, NH₄ ⁺.     

Solvent extraction of univalent cations into nitrobenzene using sodium dicarbollylcobaltate and tetraphenyl p-tert-butylcalix[4]arene tetraketone

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the equilibrium M ⁺(aq) + 1 · Na⁺ (nb) ⇄ 1 · M ⁺ (nb) + Na⁺ (aq) taking place in the two-phase water-nitrobenzene system (M ⁺ = Li⁺, H₃O⁺, NH₄ ⁺, Ag⁺, K⁺, Rb⁺, Tl⁺, Cs⁺; 1 = tetraphenyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the 1 · M ⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Cs⁺ < Rb⁺ < Tl⁺ < K⁺ < NH₄ ⁺ < Ag⁺ < H₃O⁺ < Li⁺. Correspondence: Emanuel Makrlík, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czech Republic.     

Effect of ligand on the redox reactions of thallium metal clusters

Pulse radiolysis of an aqueous solution of mono-valent thallium ion and mixed solutions of Tl⁺/Ag⁺ in the presence of various amino polycarboxylic acids such as trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (DCTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) and triethylenetetraminehexaacetic acid (TTHA) has been carried out. Abnormal valence states of Tl ions were generated. It is concluded that DCTA, DTPA, HEDTA and TTHA decrease the redox potential of Tl ions in aqueous solutions. It was observed that the electron transfer from complexed Tl₂⁺ to Ag⁺ varied in the range 7.5 × 10⁸ to 1.0 × 10⁹, depending on the type of complexing ligand. Electron transfer from Tl₂⁺ to Ag⁺ lead to the formation of silver atoms, which agglomerate further to form silver colloid.     

Spectrophotometric Study of Complexation of Tri-Aza Dibenzosulfide and Dibenzosulfoxide Macrocyclic Compounds with Heavy Metal Ions

The complexation reactions between 7,10,13-triaza-1-thia-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione ( TTD ) and 7,10,13-triaza-1-sulfoxo-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione ( TSD ) macrocycles with Ag⁺, Cd²⁺, Cu²⁺, Pb²⁺, Sr²⁺, Tl⁺, and Zn²⁺ ions have been studied in ethanol and methanol solutions at 25°C. The complexes formed between macrocycles ( TTD ) and ( TSD ) with these metals cations had a stiochiometry of 1:1 and 1:2, respectively. The stability constants of the resulting complexes were determined and found to decrease in the order Cu²⁺ > Zn²⁺ > Ag⁺ > Tl⁺ > Cd²⁺ > Pb²⁺ > Sr²⁺ with macrocycle ( TTD ) and Tl⁺ > Zn²⁺ > Cd²⁺ > Pb²⁺ > Cu²⁺ > Ag⁺ > Sr²⁺ with macrocycle ( TSD ).     

Oxidations with alkaline permanganate using formic acid for back-titration: Determination of lead and thallium

Pb⁺² (~37-0.6mg) and Tl⁺ (45-0.9 mg) can bc estimated by mixing with KmnO₄ in presence of Ba⁺² ions and I_NNaOH. The excess KmnO₄ is then titrated with formic acid.A mixture of Pb⁺² and Tl⁺ is oxidized simultaneously with KMn0₄ in 0.1N NaOH. Pb⁺² interferes also when precipitated as sulphate or tellurate. In presence of SO₄^-2 and telluric acid, thallium can be titrated only when its concentration is not less than 30 mg, below which lead seriously interferes. Tl⁺ can be accurately determined in the filtrate from the PbS0₄ precipitate.     

Bis-salicylaldehyde-ethylenediamine as an analytical reagent

Summary Copper has been determined gravimetrically as its bis-salicylaldehyde-ethylenediamine complex of the composition C₁₆H₁₄O₂N₂ · Cu, dried at 100–120° C. The complex is completely precipitated in theph range of 10.5–13.5, adjusted with ammonia or caustic alkali. It is stable in presence of excess ammonia, 0.1 N alkali, ammonium salts and complexing agents as tartrate, citrate, sodium-thiosulphate, fluoride, thiourea, triethanolamine and EDTA. In presence of tartrate and ammonia the ions of alkali metals, alkaline earths, Ag⁺, Tl⁺, Tl³⁺, Pb²⁺, Cd²⁺, Co²⁺, Mn²⁺, Pd²⁺, Al³⁺, Cr³⁺, La³⁺, Ce³⁺, Au³⁺, Pt⁴⁺, Ti⁴⁺, Zr⁴⁺, Th⁴⁺, UO₂ ²⁺ and anions as VO₃ ^–, MoO₄ ^2–, WO₄ ^2–, CrO₄ ^2–, PO₄ ^3–, AsO₄ ^3– do not interfere. Ni²⁺ and Hg²⁺ are masked by tartrate, EDTA and ammonia; As³⁺, Sb³⁺ and Sn²⁺ are separated using fluoride as the complexing agent; at an alkalinity of 0.1 N caustic alkali in presence of tartrate As³⁺, Sb³⁺, Sn²⁺, Bi³⁺, Zn²⁺ and Fe³⁺ are separated. Fe³⁺ can also be separated using triethanolamine as the masking agent at aph of about 13.0. Copper can be separated from almost all the ions, thus affording a highly selective method for the determination of copper.

---

Zusammenfassung Es wird eine gravimetrische Methode zur Bestimmung von Kupfer beschrieben, die auf der Bildung des Bis-salicylaldehyd-äthylendiaminkomplexes beruht. Dieser hat die Zusammensetzung C₁₆H₁₄O₂N₂ · Cu. Die Fällung wird imph-Bereich 10,5–13,5 (mit Ammoniak oder Alkalilauge eingestellt) vorgenommen und der Niederschlag bei 100°–120° C getrocknet. Der Komplex ist beständig in Gegenwart von überschüssigem Ammoniak, 0,1 n Alkali, Ammoniumsalzen sowie Tartrat, Citrat, Natriumthiosulfat, Fluorid, Thioharnstoff, Triäthanolamin und ÄDTA. In Gegenwart von Tartrat und Ammoniak stören nicht: Alkalien, Erdalkalien, Ag⁺, Tl⁺, Tl³⁺, Pb²⁺, Cd²⁺, Co²⁺, Mn²⁺, Pd²⁺, Al³⁺, Cr³⁺, La³⁺, Ce³⁺, Au³⁺, Pt⁴⁺, Ti⁴⁺, Zr⁴⁺, Th⁴⁺, UO₂ ²⁺ sowie VO₃ ^–, MoO₄ ^2–, WO₄ ^2–, CrO₄ ^2–, PO₄ ^3– und AsO₄ ³⁺. Ni²⁺ und Hg²⁺ können mit Tartrat, ÄDTA und Ammoniak maskiert werden, As³⁺, Sb³⁺ und Sn²⁺ mit Fluorid. In 0,1 n ätzalkalischer Lösung in Gegenwart von Tartrat können As³⁺, Sb³⁺, Sn²⁺, Bi³⁺, Zn²⁺ und Fe³⁺ abgetrennt werden. Fe³⁺ kann ebenfalls mit Triäthanolamin beiph 13,0 maskiert werden. Das beschriebene Verfahren erlaubt somit eine Abtrennung des Kupfers von fast allen anderen Ionen.

---

---

Part I: Singh, B. R., and S. Kumar: Z. analyt. Chem. 185, 211 (1962).