Sodium oxalate extractant

In one acid digestion process, monazite sand is heated with 93% sulfuric acid at 210°C. The solution is diluted with water and filtered. Filtrate containing thorium and rare earths is treated with ammonia and pH is adjusted to 1.0. Thorium is precipitated as sulfate and phosphate along with a small fraction of rare earths. The precipitate is washed and dissolved in nitric acid. The solution is treated with sodium oxalate. Thorium and rare earths are precipitated from this nitric acid solution as oxalates. The oxalates are filtered, washed, and calcined to form oxides. The oxides are redissolved in nitric acid and the acid solution is extracted with aqueous tributyl phosphate. Thorium and cerium (IV) separate into the organic phase from which cerium (IV) is reduced to metalhc cerium and removed by filtration. Thorium then is recovered from solution. 

If the starting material is gadolinite, ore is digested with hydrochloric or nitric acid. Rare earths dissolve in acid. The solution is treated with sodium oxalate or oxalic acid to precipitate rare earths as oxalates. For euxenite, ore is opened either by fusion with potassium bisulfate or digestion with hydrofluoric acid. If monazite or xenotime is extracted, ore is either heated with sulfuric acid or digested with caustic soda solution at elevated temperatures. 

Ytterbium oxide is produced as an intermediate in recovering ytterbium from minerals (See Ytterbium). After opening the ore by digestion with concentrated sulfuric acid or caustic soda solution at high temperatures, rare earths are separated by ion exchange, solvent extraction, or fractional precipitation. Ytterbium fraction is treated with oxahc acid or sodium oxalate to precipitate jdterbium oxalate, which is ignited to yield ytterbium oxide. 

Although the free phenolic structures are oxidized faster, chlorine dioxide also destroys nonphenolic phenyl propane units and double bonds present in the pulp chromophores. After cleavage of the benzene ring various di-carboxylic acids are formed, such as oxalic, muconic, maleic, and fumaric acids in addition to products substituted with chlorine (Fig. 8-10). As a result of depolymerization and formation of carboxyl groups the modified lignin is dissolved during the chlorine dioxide treatment and in the sodium hydroxide extraction stage that usually follows. 

Cow s milk (congener specific) Mixing of sample fortified with C-labeled PCBs with sodium oxalate and methanol solvent extraction cleanup and HRGC/MS 0.1-0.5 pg/g (fat) for tetra- to hexa-congeners of PCB 50-60 Van der Velde et al. 1994... 

Chestnut (Castanea sativa) extract Chromium hydroxide (ic) Chromium sulfate, basic Dihydroxyacetone Gallic acid Isobutyric acid Resorcinol Sodium oxalate Zirconium tetrachloride tanning agent, leather... 

An alternative American process uses a feed produced by oxalate precipitation of thorium and rare earths. This precipitate is calcined to the oxides and dissolved in nitric acid for extraction with undiluted TBP. After stripping with 8N nitric acid, a high proportion of cerium extracts with the thorium, but the other rare earths are eliminated. The cerium is then back-washed in a separate extractor by means of 0 1 N sodium nitrite solution, which reduces it to the solvent-insoluble cerous condition. Thorium is then backwashed in the last extractor with either water or 2 per cent sulphuric acid. In order to make this process economic it was necessary to devise an efficient system of oxalic acid recovery. This was based upon treatment of the thorium and rare earth oxalates with sodium hydroxide and recycling the resulting sodium oxalate to the precipitation stage. 

Diethyl oxalate. Reflux a mixture of 45 g. of anhydrous oxalic acid (1), 81 g. (102-5 ml.) of absolute ethyl alcohol, 190 ml. of sodium-dried benzene and 30 g. (16-5 ml.) of concentrated sulphuric acid for 24 hours. Work up as for Diethyl Adipate and extract the aqueous laj er with ether distil under atmospheric pressure. The yield of ethyl oxalate, b.p. 182-183°, is 57 g. 

Urea oxalate is also sparingly soluble in amyl alcohol and since urea is soluble in this alcohol, the property may be utilised in separating urea from mixtures. An aqueous extract of the mixture is rendered slightly alkaline with sodium hydroxide solution and extracted with ether this removes all the basic components, but not urea. The residual aqueous solution is extracted with amyl alcohol (to remove the urea) upon adding this extract to a solution of oxalic acid in amyl alcohol crystalline urea oxalate is precipitated. 

Androst-4-ene-3,17-dione. Testosterone (0.58 g, 2 mmoles) is dissolved in a solution prepared from 3 ml of benzene, 3 ml of dimethyl sulfoxide, 0.16 ml (2 mmoles) of pyridine and 0.08 ml (1 mmole) of trifluoroacetic acid. After addition of 1.24 g (6 mmoles) of dicyclohexylcarbodiimide, the sealed reaction flask is kept overnight at room temperature. Ether (50 ml) is added followed by a solution of 0.54 g (6 mmoles) of oxalic acid in 5 ml of methanol. After gas evolution has ceased ( 30 min) 50 ml of water is added and the insoluble dicyclohexylurea is removed by filtration. The organic phase is then extracted twice with 5 % sodium bicarbonate and once with water, dried over sodium sulfate and evaporated to a crystalline residue (0.80 g) which still contains a little dicyclohexylurea. Direct crystallization from 5 ml of ethanol gives androst-4-ene-3,17-dione (0.53 g, 92%) in two crops, mp 169-170°. 

To a solution of dihydronaphthalene 41 (250 mg, 0.77 mmol) in CH2CI2 (5 mL) was added methyl trifluoromethanesulfonate (227 mg, 1.38 mmol). The mixture was stirred at rt until the starting material had been completely consumed as judged by TLC analysis (3 h). The mixture was cooled to 0°C and a solution of NaBHt (111 mg, 2.92 mmol) in 4 1 MeOH THF (3 mL) was slowly added. The mixture was warmed to rt then quenched with saturated aqueous ammonium chloride (50 mL). The resulting mixture was extracted with CH2CI2 (3 X 50 mL) and the combined organic extracts were dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The resulting material was dissolved in 4 1 THF/H2O (5 mL) and oxalic acid (485 mg, 3.85 mmol) was added. The reaction... 

Synthesis of 9-oxo-11 CH,1 Sol-bis-(2-tetrahydropyranytoxy)-16,16-dimethyl-prosta-trans-2, trans-13-dienoicacid 4gof ethyl 9a-hydroxy-1 la,1 5a-bis-(2-tetrahydropyranyloxy )-16,16-dimethyl-prosta-trans-2,trans-13-dienoate were dissolved In 130 ml of a mixture of ethanol-water (3 1), mixed with 3.9 g of potassium hydroxide and stirred at 25°C for 2 hours. The reaction mixture was acidified with aqueous solution of oxalic acid to pH 5, and diluted with 100 ml of water, extracted with ethyl acetate. The extracts were washed with water, dried over sodium sulfate and concentrated under reduced pressure to obtain 3,88 g of 90 -hydroxy-11a,15a-bis-(2-tetrahydropyranyloxy)-16,16-dimethyl-prosta-trans-2,trans-13-dienoic acid. 

Polymer Labs. PLRP-S Gradient A 0.001 M oxalic acid, 0.5% formic acid + 3% THF in water, B = THF Positive ESF MS/MS OTC, CTC, TC, DC, and its 4-epimer in pig tissues Extraction with sodium succinate solution, protein removal with TCA, SPE cleanup on polymeric RP column DL = 0.5-4.2 ng/g [57]... 

The mash from the Streptomyces aureofaciens fermentation broth is acidified and filtered. The filtrate is adjusted to the desired pH, usually 7-8.5, and various flocculating or chelating agents may be added (e.g., vinyl acetate-maleic anhydride copolymer, sodium EDTA, ammonium oxalate, Arquad). The precipitate is (1) stirred with filter aid, filtered, stirred with HC1, refiltered, mixed with 2-ethoxyethanol, filtered, washed, and the filtrates are combined, acidified with HC1, NaCl is added, and the crystals are collected, washed with 2-ethoxyethanol, water, and ethanol, and dried (67), or (2) extracted into methyl isobutyl ketone, the extracts are combined, filtered, and acidified with HC1, and the crystals are collected and washed with water, 2-ethoxyethanol, and isopropanol, and vacuum-dried. If the crystals are greenish, they are treated with sodium hydrosulfite at pH 1.8, filtered, washed, and dried as in (1) above (68). 

Fig. 2. Sequential extraction of Arsenic (MG-magnesium chloride, PHOS-sodium hypo phosphate, HCL-hydrocihoric acid, OX-oxalic acid, ToCEB- titanium chloride with EDTA, NIT- nitric acid).

In a 1-1., round-bottomed flask is placed 72 g. of the crude oxazolidine in 600 ml. of water, and 201.6 g. (1.6 moles) of hydrated oxalic acid is added. The mixture is then heated under reflux for 1 hour, cooled, treated with 600 ml. of water to dissolve precipitated oxalic acid, and extracted with three 100-ml. portions of ether. The combined ethereal extracts are washed with 50 ml. saturated sodium bicarbonate solution and then dried over anhydrous potassium carbonate. Concentration of the ethereal solution gives 30-35 g. of crude aldehyde. Distillation of this material at 70-75° (1.5 mm.) gives pure o-anisaldehyde (22.8—26.3 g. 51-59%), m.p. 35.5-38° (Note 9). 

C. 1 -Phenylcyclopentanecarboxaldehyde. The crude tetrahy-drooxazine (25.0 g., 0.092 mole) from Part B is heated at reflux with 300 ml. of water containing 37.8 g. (0.300 mole) of oxalic acid dihydrate for 3 hours. The solution is cooled, and the aldehyde is extracted with four 150-ml. portions of petroleum ether (b.p. 40-60°). The organic extracts are combined and washed with 10 ml. of saturated sodium bicarbonate solution and dried with anhydrous powdered magnesium sulfate. The petroleum ether is removed by distillation with a rotary evaporator, and the product is distilled through a Vigreux column to give 7.8-8.7 g. (50-55%) of 1-phenylcyclopentane-carboxaldehyde, b.p. 70-73° (0.1 mm.) n26-BD 1.5350, infrared spectrum (neat) 1720 cm.-1 (C= 0) (Note 12). 

Various processes separate rare earths from other metal salts. These processes also separate rare earths into specific subgroups. The methods are based on fractional precipitation, selective extraction by nonaqueous solvents, or selective ion exchange. Separation of individual rare earths is the most important step in recovery. Separation may be achieved by ion exchange and solvent extraction techniques. Also, ytterbium may be separated from a mixture of heavy rare earths by reduction with sodium amalgam. In this method, a buffered acidic solution of trivalent heavy rare earths is treated with molten sodium mercury alloy. Ybs+ is reduced and dissolved in the molten alloy. The alloy is treated with hydrochloric acid, after which ytterbium is extracted into the solution. The metal is precipitated as oxalate from solution. 

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