Extraction Of Thiocyanate Research Articles

Studies on the Solvent Extraction of Metal Perchlorates III. Extraction Equilibria of Alkaline Earth Ions with Trioctylphosphine Oxide as Perchlorate and Thiocyanate

Abstract Solvent extraction of alkaline earth metal ions in 1 mol dm−3 sodium perchlorate or thiocyanate aqueous solution with trioctylphosphine oxide (TOPO) in hexane was studied at 25 °C. The extraction in both systems improved in the order: beryllium(II)>calcium(II)>strontium(II)\simeqmagnesium(II)\simeqbarium(II). When the TOPO concentration was the same, the extraction of beryllium or calcium thiocyanate was better than that of the perchlorate, that of magnesium or strontium thiocyanate was nearly similar to that of the perchlorate, while barium perchlorate was extracted better than its thiocyanate. From these results it was concluded that these five perchlorates and strontium and barium thiocyanates were extracted as ion-pairs, [M(topo)4]2+(X−)2, (X−=ClO4− or SCN−), while beryllium thiocyanate was extracted as solvates of noncharged complexes, M(SCN)2(topo)n, (n=2 and 3), and that magnesium and calcium thiocyanates in the organic phase (n=3 and 4) should have both ionic and coordinative properties. The poor extraction of magnesium salts was assumed to be due to their strong hydration.

Liquid—liquid extraction of osmium thiocyanate with hexamethylphosphoramide and direct spectrophotometric determination in the organic phase

The use of hexamethylphosphoramide (HMPA) in the osmium-thiocyanate system makes the method more sensitive and selective. The blue colour formed by osmium(VIII) with thiocyanate in 1.5 M hydrochloric acid is intensified in the presence of HMPA and the complex becomes readily extractable into chloroform. The colour system has its absorption maximum at 595 nm and obeys Beer's law over the range 0.5–16 μg of Os per ml. The optimum range is 2–10 μg/ml. The molar absorptivity is 2.09 × 10 4l.mole −1.cm −1. The method is simple, sensitive and free from interference from many metal ions, including ruthenium and other platinum metals.

Determination of niobium in steels

The determination of niobium at levels of 0.01% and below is required in certain specifications for stainless-steel welding electrodes, containing 2–3% molybdenum and 0.01% titanium. A method has been developed, based on initial extraction of niobium thiocyanate into butyl acetate followed by stripping with fluoride and re-extraction of niobium thiocyanate after masking of the fluoride by addition of boric acid. The absorbance of the extract is measured at 385 nm. Mo, Ti, V and W can be tolerated at 50 times the concentration of Nb. For higher amounts of Mo, corrections can also be applied. Ta should, however, be restricted to ten times the Nb level. Precision and accuracy of the method are satisfactory. The time taken for an individual determination is about an hour. The method is applicable to mild, low-alloy, stainless and niobium-stabilized steels.

Liquid-liquid extraction of ferric thiocyanate with hexamethyl phosphoramide: Direct spectrophotometric determination in the organic phase

Liquid-liquid extraction of ferric thiocyanate with hexamethyl phosphoramide: Direct spectrophotometric determination in the organic phase

Liquid-liquid extraction of titanium thiocyanate with hexamethylphosphoramide and direct spectrophotometric determination in the organic phase

Liquid-liquid extraction of titanium thiocyanate with hexamethylphosphoramide and direct spectrophotometric determination in the organic phase

Liquid—liquid extraction of molybdenum thiocyanate with hexamethyl phosphortriamide and direct spectrophotometric determination in the organic phase

A sensitive and selective method for estimation of trace molybdenum with fairly common reagents has been developed. The Mo—thiocyanate complex is extracted with hexamethyl phosphortriamide and chloroform from 0.75–1.5 M hydrochloric acid. The molar absorptivity is 1.76 × 10 4 1.mole −1.cm −1. The system obeys Beer's law at 460nm over the molybdenum concentration range 0.75–5ppm. The method is simple, rapid, and requires no additional reducing agent. It is generally free from interference by most of the metals commonly associated with molybdenum, including rhenium. Molybdenum in alloy steel has been successfully determined.

Spectrophotometric determination of titanium(IV) as a mixed thiocyanate—monooctyl-α-anilinobenzylphosphonate complex

Extraction of titanium(IV) thiocyanate complexes by monooctyl-α-anilinobenzylphosphonate (MOABP) dissolved in chloroform has been investigated as a function of hydrochloric and sulfuric acid concentration. Chloroform solutions follow Beer's law and are stable for at least 24 h. A sensitive and reproducible spectrophotometric determination of titanium is possible. Two complexes were identified; the first formed at acid concentrations less than 1 M, has the ratio Ti:SCN:MOABP 1:1:2 and the second, formed at higher acidity, has the ratio Ti:SCN:MOABP 1:2:2. The method is based on the extraction of titanium thiocyanate with MOABP from either 0.5 M H2SO4, and measurement of the absorbance at 336 nm (ϵ = 11 000 l mol -1 cm -1 ), or from 6.5 M HCl, and measurement of the absorbance at 420 nm (ϵ = 22 000 l mol -1 cm -1). The polymerization of thiocyanate has been studied; isoperthiocyanic acid has been identified as the polymerization product. Although both procedures give reproducible results, extraction from 6.5 M HCl is more sensitive, fewer elements interfere, and the precipitation of isoperthiocyanic acid is avoided.

Effets des cations alcalins et pseudo-alcalins sur quelques équilibres et en particulier sur l'équilibre d'extraction de l'acide thiocyanique par la méthylisobutylcétone

The equilibrium constant for the extraction of thiocyanic acid by methylisobutyl ketone at constant ionic strength, depends on the nature of alkaline cations present in the aqueous phase. The phenomenon could be explained by the existence of ion pairs for which the association constant Kp is derivable. However the extraction of chlorpromazinium thiocyanate by the same solvent and the formation of the monothiocyanate complex of zirconium in aqueous phase are both independent of the nature of the electrolyte. The observed variations for the extraction of thiocyanic acid which exist also for the extraction of hydrochloric and perchloric acids by methylisobutyl ketone, result from the variation of species activities with a change in the identity of the cations.

Liquid–liquid extraction of thiocyanate and thiocyanatoferrate(III) complexes with tris(3,5,5-trimethylhexyl)amine

The distribution ratio of iron(III) at initial concentration 10–4M has been measured using aqueous solutions of potassium nitrate and thiocyanate, at pH 2, with ionic strengths 0·25 and 0·50M, and an organic phase of tris(3,5,5-trimethylhexyl)amine in benzene. Concentrations of thiocyanate and of the amine were varied. An extraction equation was derived and found to be in good agreement with the results up to a thiocyanate concentration of 0·025M. Values of extraction equilibrium constants were calculated in several ways.

Planning of an experiment in the study of the extraction of scandium thiocyanate with chloroform solutions of 1,10-phenanthroline and collidine

1. Second-order regression equations, characterizing the extraction of scandium thiocyanate by chloroform solutions of 1,10-phenanthroline and collidine, were obtained by the method of mathematical planning of experiments. 2. The optimum conditions of extraction of scandium were found.

Study of the process of extraction of 1,10-phenanthroline- and collidine-thiocyanate complexes of scandium

1. The mechanism of the extraction of scandium thiocyanate with 1,10-phenanthroline and collidine against a background of NaCl and NaNO3 was studied by the method of mathematical planning of experiments (the method of two-dimensional cross sections). 2. In the case of the 1,10-phenanthroline-thiocyanate complex, the background electrolyte NO3− is inserted into the complex; in the case of the collidine-thiocyanate complex, the background electrolytes NO3− and Cl− are not inserted into the complexes.

Studies of the Liquid-Liquid Partition Systems. VII. The Solvent Extraction of Mercury(II) Chloride, Bromide, Iodide and Thiocyanate with Some Organic Solvents

Abstract The liquid-liquid distribution of mercury(II) has been determined when the organic phase was benzene, hexane containing tributylphosphate(TBP), methylisobutylketone(MIBK), or nitrobenzene, and when the aqueous phase was 0.5m sodium per chlorate containing chloride, bromide, iodide, or thiocyanate ions. The stability constants for the mercury(II) complexes in the aqueous phase and the distribution constants for the extractable complexes were determined by a graphic analysis of the distribution data, which were measured as a function of the ligand concentration. It was concluded that the stability constants determined from the present results agree almost entirely with the previous values and that the only extracted species into benzene and hexane containing TBP is the non-charged complex (HgX2, where X− is the ligand) in all cases, whereas those extracted into MIBK or nitrobenzene include not only the non-charged but also the charged species (HgX3− and sometimes HgX42−) except in the case of the chloride system. The distribution ratio in the hexane-TBP system was further determined by changing the TBP concentration in the hexane phase, and the equilibrium constants for the adduct formation between the HgX2 species and TBP molecules were determined. Finally, some discussion was made of the relation between the distribution behavior of the mercury(II) complexes and the natures of the ligands and the solvents.

Extraction of scandium thiocyanate with pyridine derivatives

1. The possibility of the extraction of scandium by the thiocyanate ion and a chloroform solution of α- and β-picolines, 2-methyl-5-ethylpyridine, and collidine was demonstrated. 2. The extraction of scandium by collidine was investigated at various concentrations of the reagents and scandium, acidities of the solution, times of contact of the phases, and in the presence of NaCl, NaNO3, and NaClO4. The composition of the complex of scandium thiocyanate with collidine corresponds to the formula ColH+[Sc(SCN)4(Col)2]. The extraction of Fe(III), Y, Zr, and Th was studied under the optimum conditions for the extraction of scandium.

Extraction of lanthanides by quaternary ammonium salts-I Extractions of ammonium thiocyanate and chloride

It has been shown that ammonium thiocyanate is extracted by thiocyanate hydrate salt of Quatamin T-08 ((C n H 2 n+1 ) 3 CH 3NSCN (H 2O) prop;: average n = 10, χ ≈ 1) in toluene and a 1 : 1 complex is formed between the solvent and ammonium thiocyanate in the organic phase. When the chloride salt of the quaternary ammonium extracts ammonium chloride, a similar extraction reaction takes place. When ammonium thiocyanate is present in the aqueous phase, the quaternary ammonium chloride is converted to the thiocyanate salt quantitatively even though a large amount of ammonium chloride exists in the aqueous phase. The presence of ammonium chloride in the aqueous phase enhances the extraction of ammonium thiocyanate.

Liquid–liquid extraction of beryllium thiocyanate

Liquid–liquid extraction of beryllium thiocyanate

Liquid-liquid extraction of cobalt thiocyanate with trhsooctylamine

Cobalt forms a coloured complex with triisooctylamine and thiocyanate in carbon tetrachloride. The green organic phase has maximum absorbancc at 627.5 mμ and Beer's law is obeyed in the range 0–10 mg Co. The molar extinction coefficient is 1895. The distribution coefficient at room temperature is 5.6. A composition of the coloured species is proposed.