Cobalt 2 with thiocyanate

Cobalt, pentaamminecyano-isomerization, 1,186 Cobalt, pentaamminehydroxy-thiocyanate isomerization, 1,185 Cobalt, pentaammineisonicotinamido-electron transfer, 1,373 with hexaaquachromium, 1,369 reduction... 

One-phase titration methods have also been developed. These methods are not truly one-phase titrations but the term is used to indicate the absence of a second organic phase. One of these methods, applied to the analysis of sodium and triethanolamine lauryl sulfates and lauryl ether sulfates, use a quaternary amine as a titrant and cobalt(II) thiocyanate as indicator. Centrimide was found to avoid the use of chloroform which was not possible with other titrants examined, such as domiphen bromide and oxyphenonium bromide. The pink color of the indicator changes to violet as an excess of titrant forms a complex with the indicator [238]. 

Hassan et al [65] used a method for the determination of primaquine and other antimalarials, through ternary complex formation. The analytical aspects of the reaction between the widely used antimalarial drugs with cobalt and thiocyanate to form ternary complexes are described. Alternatively, determination of the cobalt content of the nitrobenzene extract using atomic absorption spectroscopy provided an indirect method for the determination of the drugs. Both methods are applied to the analysis of pharmaceutical preparation and the results obtained agreed well with those obtained with official methods. 

Dr. Pearson presented data on the optical density observed when the nitrato-cobaltic complex reacts with thiocyanate ion, and there is nothing to object to in these results. But I think one might be concerned about the theoretical curve calculated using the competition ratio in a table wrhich Haim and Taube presented in the journal. 

The amount of ammonia volatilized was determined from the amount of standard sulfuric acid consumed in the traps. Ethylenediamine was determined by the salicylaldehyde method (14). The sample for cobalt(II) determination was made slightly acidic with hydrochloric acid immediately upon removal of the sample from the reaction flask, in order to prevent further oxidation of the cobalt (18). The carbon was removed by filtration, and the cobalt (II) concentration was determined spectrophotometrically as the cobalt-ammonium thiocyanate complex, (NH4)2Co(NCS)4 (28). 

Cobalt from acidified sea water is extracted by anion exchange on the strongly basic resin Amberlite CG 400 (SCN ) after complexation of Co2+ with thiocyanate. Distribution coefficients of cobalt(II) up to 1.9 x 104 are attainable in solutions of 1 M NH4SCN and 0.1 M HC1. Cobalt sorbed on the resin column is stripped by elution with 2 M perchloric acid 74). 

The cobalt(ll) thiocyanate complex can be extracted with oxygen-containing solvents, such as a mixture of diethyl ether with isoamyl alcohol (1+1), MIBK, or acetylacetone [23,24], The molar absorptivity, e, of the complex in the ether-isoamyl aleohol mixture is about 30% smaller than in the aqueous acetone media. 

The anionic cobalt(II) thiocyanate complex reacts with many organic bases to form ion-associates which can be extracted into CHCI3, or other non-polar solvents. Organic reagents used for this purpose include DAM [25], TOA [26], triphenylsulphonium ion [27], or 2,4-dichlorobenzyltriphenylphosphonium ion [28],... 

A solution of 6 ml. of diethylenetriamine in 50 ml. of absolute ethanol is slowly added to a solution of 10 g. (0.057 mol) of cobalt(II) thiocyanate and 5 g. (0.051 mol) of potassium thiocyanate in 200 ml. of absolute ethanol. A tan precipitate begins to form almost immediately. Air, dried by passage through a bed of a desiccant, is bubbled through the mixture for one hour. The precipitate is filtered with suction and washed with absolute ethanol until the washings are colorless. Care must be taken not to suck the precipitate dry. A final wash is made with ether and the compound is stored in a desiccator. The yield is 18 g. (95%). Anal. Calcd. for ICo(dien)(SCN)d Co, 17.50 C, 24.98 S, 28.60. Found Co, 17.55 C, 24.90 S, 28.40. 

Cobalt(II) thiocyanate test to the test solution add an equal volume of the reagent (about 10%, freshly prepared), and stir the wall of the vessel with a glass rod. A deep-blue crystalline precipitate of cobalt tetrathio-cyanatomercurate(II) is formed ... 

Amodiaquine reacts with cobalt and thiocyanate to yield stable ternary complexes. These complexes are readily extractable in nitrobenzene to give a greenish-blue color with maximum absorption at 625 nm that can be used for quantitative determination. The mean recoveries for authentic samples of amodiaquine hydrochloride are 100.81 1.77% (p = 0.05). Alternatively, determination of the cobalt content of nitrobenzene extract by atomic absorption spectroscopy provides an indirect method for the determination of the drug with a mean recovery of 99.99 2.16%. Both the methods have been successfully applied to the assay of the drug in pharmaceutical preparations (30). 

With thiocyanate ions cobalt ions form a complex (Co(SCN)4)2-. When tetra-phenyl arsonium chloride (C6H3)4AsCl is added a blue compound is formed which can be directly extracted with chloroform and measured photometrically at 620 nm. 

Lane [17] has separated long chain tertiary amines on alumina G layers, using isobutyl acetate or isobutyl acetate-acetic acid (98 + 2). The tertiary amines and also any primary or secondary amines present as impurities, are detected with cobalt(II) thiocyanate (Rgt. No. 53). The amines appear as blue spots on a pink background. The colours fade after about 2 hours but can be restored by spraying with water or placing the plate in a humid atmosphere. Long chain quaternary ammonium salts and amine oxides react similarly. 

Cobalt, nickel, chromium and copper salts reduce the sensitivity of the iron test because of the color of their ions, or of their reaction products with thiocyanate. However 1.25 y iron can be detected in the presence of 320 times the amount of cobalt or chromium, and 0.025 y iron in the presence of 640 times the amount of nickel or copper. ... 

Cobalt i salts give a blue solution with thiocyanates in the presence of acetone. This color reaction applied for the detection of cobalt (see page 200) may be used as a test for thiocyanate. 

Large amounts of halides, especially iodides, give only a slight greenish color under these conditions. However, 6 y thiocyanate may be detected in the presence of 1000 times the amount of iodide, bromide, chloride, thiosulfate and acetate. The latter two ions, on evaporation with cobalt salts, give a green color which, unlike that developed by thiocyanate, does not enter the acetone. Nitrites interfere because they react with thiocyanates to give red nitrosyl thiocyanate. 

Test by mutual precipitation of zinc and cobalt with mercury thiocyanate ... 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenyiarsonium chloride in an organic solvent. Titanium(IV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenyiarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates deterrnined spectrophotometricaHy. Cobalt, palladium, tungsten, niobium, and molybdenum have been deterrnined in a similar manner. In addition to their use for the deterrnination of metals, anions such as perchlorate and perrhenate have been deterrnined as arsonium salts. Tetraphenyiarsonium permanganate is the only known insoluble salt of this anion. 

According to X-ray data, 2,5-diamino-l,3,4-triazole retains its diamino form in the heterovalent cobalt complex 375 (91IC4858) and in the polymeric complex with manganese thiocyanate (93ICA53). 

Determination of copper as copper(I) thiocyanate Discussion. This is an excellent method, since most thiocyanates of other metals are soluble. Separation may thus be effected from bismuth, cadmium, arsenic, antimony, tin, iron, nickel, cobalt, manganese, and zinc. The addition of 2-3 g of tartaric acid is desirable for the prevention of hydrolysis when bismuth, antimony, or tin is present. Excessive amounts of ammonium salts or of the thiocyanate precipitant should be absent, as should also oxidising agents the solution should only be slightly acidic, since the solubility of the precipitate increases with decreasing pH. Lead, mercury, the precious metals, selenium, and tellurium interfere and contaminate the precipitate. 

Thiocyanate ions form stable complex salts, e. g. intense red with iron(lll) and pale blue with cobalt(ll) cations. 

A warmed alcoholic solution of cobalt(Il) nitrate and 2-formylpyridine S-methyldithiocarbazate, 6, yielded diamagnetic [Co(6-H)2]N03 [126]. However, cobalt(II) chloride, bromide and thiocyanate yielded complexes with cobalt(III) cations and cobalt(II) anions, [Co(9-H)2]2 [C0A4]. 

Lemli and Knockaert [33] described a spectrophotometric method for the determination of miconazole nitrate suspensions and other organic bases in pharmaceutical preparations by the use of cobalt thiocyanate. The drug and the amines (as their anhydrous hydrochlorides in dichloromethane) react with solid cobalt thiocyanate to form an ion-pair complex that contains two molecules of base to one [Co(SCN)4]2. The complex is determined quantitatively by spectrophotometry versus dichloromethane at 625 nm with rectilinear response for up to 400 pg/mL of the base. This method was applied to miconazole nitrate suspensions and the coefficient of variations were generally <2%. 

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