Cobalt -tartrate

The cadmium ion reacts with dithizone (Section 4.5) in neutral to strongly alkaline media to give a pink cadmium dithizonate, which is soluble in CCI4 and in CHCI3. The stability of Cd(HDz)2 in strongly alkaline media (5-20% NaOH) allows cadmium to be extracted from Pb, Bi, Sn(II), and Zn, the dithizonates of which cannot exist under such conditions. Dimethylglyoxime is added to mask nickel and cobalt. Tartrate prevents the precipitation of metals as hydroxides. The noble metals (Au, Pt, Pd, Ag, Hg) and Cu must be removed before cadmium is extracted. They are most simply pre-extracted with dithizone from acid medium. 

Dimethylglyoxime. The complexes with nickel and with palladium are soluble in chloroform. The optimum pH range for extraction of the nickel complex is 4-12 in the presence of tartrate and 7-12 in the presence of citrate (solubility 35-50 fig Ni mL 1 at room temperature) if the amount of cobalt exceeds 5 mg some cobalt may be extracted from alkaline solution. Palladium(II) may be extracted out of ca lM-sulphuric acid solution. 

D. Benzoin-a-oxime (cupron) (VII). This compound yields a green predpitate, CuC14Hu02N, with copper in dilute ammoniacal solution, which may be dried to constant weight at 100 °C. Ions which are predpitated by aqueous ammonia are kept in solution by the addition of tartrate the reagent is then spedfic for copper. Copper may thus be separated from cadmium, lead, nickel, cobalt, zinc, aluminium, and small amounts of iron. 

Sulphuric acid is not recommended, because sulphate ions have a certain tendency to form complexes with iron(III) ions. Silver, copper, nickel, cobalt, titanium, uranium, molybdenum, mercury (>lgL-1), zinc, cadmium, and bismuth interfere. Mercury(I) and tin(II) salts, if present, should be converted into the mercury(II) and tin(IV) salts, otherwise the colour is destroyed. Phosphates, arsenates, fluorides, oxalates, and tartrates interfere, since they form fairly stable complexes with iron(III) ions the influence of phosphates and arsenates is reduced by the presence of a comparatively high concentration of acid. 

Fluoride, in the absence of interfering anions (including phosphate, molybdate, citrate, and tartrate) and interfering cations (including cadmium, tin, strontium, iron, and particularly zirconium, cobalt, lead, nickel, zinc, copper, and aluminium), may be determined with thorium chloranilate in aqueous 2-methoxyethanol at pH 4.5 the absorbance is measured at 540 nm or, for small concentrations 0-2.0 mg L 1 at 330 nm. 

An experiment you may have carried out in previous years Involves the reaction of a solution of potassium sodium tartrate (Rochelle salt) with hydrogen peroxide, which Is catalysed by cobalt(ll) chloride solution. 

Cobalt(lll).—Complexes. Ammine complexes. Optical activity can be induced in the complexes [Co(NH3) ] and [Cofenlj] by means of outer-sphere association with chiral anions, e.g. (- - )-tartrate. Circular dichroism is observed in the d-d bands of the cations and it is suggested that this is due to (a) direct interaction between the chiral anion and the metal f/-orbitals and (b) the preferred conformation adopted by the inner-sphere ligands in the presence of a helical outer-sphere ligand. 

Co(en)33+ salts are usually prepared, but they can be resolved (i.e., separated from one another) by fractional crystallization of a salt of Co(en)33+ from solution with an anion that is itself an optical isomer, for example, the d-tartrate anion. The fact that optical isomers of Co(en)33+ and other chelates do exist was used by Werner as incontrovertible proof of his theory of octahedral coordination in cobalt(III) and other complexes. 

A secondary, more subtle, effect that can be utilized in the achievement of selectivity in cation exchange is the selective complexation of certain metal ions with anionic ligands. This reduces the net positive charge of those ions and decreases their extraction by the resin. In certain instances, where stable anionic complexes form, extraction is suppressed completely. This technique has been utilized in the separation of cobalt and nickel from iron, by masking of the iron as a neutral or anionic complex with citrate350 or tartrate.351 Similarly, a high chloride concentration would complex the cobalt and the iron as anionic complexes and allow nickel, which does not form anionic chloro complexes, to be extracted selectively by a cation-exchange resin. 

Tris (ethylenediamine) cobalt (III) chloride was first prepared by Werner.1 Resolution was effected through the chloride d-tartrate which was obtained by allowing the chloride (1 mol) to react with silver d-tartrate (1 mol). The correct ratio of chloride ion to tartrate ion is important and this has meant that it was necessary to isolate the pure solid chloride, the synthesis of which has been described by Work.2 In the present method the less soluble diastereo-isomer is isolated directly and the expensive and unstable silver d-tartrate is replaced by barium d-tartrate. The addition of activated carbon ensures rapid oxidation of the initial cobalt (II) complex and eliminates small amounts of by-products of the reaction. 

Levo iodide. The Zeyo-tris(ethylenediamine) cobalt (III) chloride d-tartrate remaining in the solution above is treated with concentrated ammonia solution (0.5 ml.) and the mixture is heated to about 80°. Solid sodium iodide (35 g.) is stirred in and the whole cooled in ice. The impure levo iodide is filtered off and washed with ice-cold 30% sodium iodide (25 ml.) and then with alcohol and air-dried, resulting in a yield of 27 g. Purification is effected by stirring the whole of the crude material into 65 ml. of water heated to 50°. The racemate remains undissolved and is filtered off. Sodium iodide (10 g.) is added to the warm filtrate (50°) and crystallization allowed to take place. After cooling in ice the solid is filtered, washed with ethanol and then acetone, and air-dried. The yield is 18 g. (26%), and [a]D = -90°. Anal. Calcd. for [Co(en)3]I3-H20 C, 11.26 H, 4.11. Found C, 11.43 H, 4.01. 

Solutions of cobalt(II) sulfate heptahydrate (28.1 g. 0.1 mol) and sodium d-tartrate (23.0 g. 0.1 mol), each dissolved in 50 ml. of water at 65°, are mixed and stirred. After about a minute purple-red cobalt (II) d-tartrate separates and the mixture is maintained at 65° for 15 minutes, then cooled in ice, and filtered. The precipitate is washed with 50 ml. of ice water, then acetone, and air-dried. Ethylenediamine (20.4 ml. of 88.6% w/v 0.3 mol) is placed in a 500-ml. filter flask fitted with a rubber stopper and a... 

The C2S-dinitrobis(ethylenediamine)cobalt(III) ion was first resolved by Werner1,213 through the d-camphorsulfo-nate. However, that method, though it ultimately gives good yields of both optical antipodes, is laborious, and the resolving agent is comparatively expensive. Resolution is readily accomplished by the use of potassium cZ-antimony tartrate, and yields of each antipode of the order of 40 to 50% are obtained. 

Barium hexafluorosilicate, preparation of, for decomposition to silicon tetrafluoride, 4 145 Barium paraperiodate (orthoperiodate), Ba3H4(I06)2, 1 171 Barium dezZro-tartrate, for resolution of tris(ethylenediamine)-cobalt(III) ion, 6 184 Barium thiocyanate, 3 24 Benzalazine, in recovery of hydrazine residues, 1 92 Benzoylacetone, beryllium derivative of, 2 19... 

Tris (ethylenediamine) cobalt (III) ion, resolution of, through chloride dextro-tartrate, 6 183 synthesis of dextro-, through chloride dextro-tartrate, 6 186 Tris (ethylenediamine) nickel (II) chloride, 2-hydrate, 6 200 Trisilane, octachloro-, 1 44 Trisilicon octachloride, 1 44 Tris(2,4-pentanedionato)aluminum, 2 25... 

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