Ammonium oxalic acid solution

Place 50 mL sample in a Nessler tube. Add 1 mL of 1 1 HC1 and 2 mL ammonium molybdate reagent. Shake well. Let the solution stand for 5 min. Add 2 mL oxalic acid solution, shake thoroughly, and allow the solution to stand for another 5 min. Measure the absorbance of the yellow color developed at 410 nm. Run a blank using 50 mL distilled water following the above procedure. Compare the absorbance of the sample solution with the standards and determine the concentration of silica from the calibration curve. 

Oxalic acid solution white precipitate of zirconium oxalate, readily soluble in excess of the reagent and also in ammonium oxalate solution (difference from thorium). 

Separation. Cerium and thorium salts are precipitated in Group IIIA. They may be separated from the other metals of the group by dissolving the precipitate in dilute HC1 and adding oxalic acid solution, when the oxalates of both metals are precipitated. The thorium and cerium may be separated (a) by dissolving the thorium oxalate in a mixture of ammonium acetate solution and... 

Phosphorus Distribution. The major sediment phosphorus fraction is that extracted by hydrochloric acid (Table III). Ammonium oxalate-oxalic acid solution extracts somewhat less phosphorus than hydrochloric acid, while sodium hydroxide as well as hydroxylamine extract much less. 

The insertion of Ti in the zeolite framework was accompanied by a significant decrease in A1 content (Table 1). However, there was no stoichiometric process between A1 removal and Ti insertion. Moreover, it was found that the treatment of Ig of an aluminum containing beta zeolite with a 75 ml of 3 x 10 M oxalic acid solution decreased the Si/Al ratio from its original value of 30 to 85 due to A1 extraction. Attempts to incorporate Ti into other zeolites like ZSM-12 and mordenite were not successful. Interestingly, the extraction of A1 from these zeolite structures was also unsuccessful with oxalic acid solutions with comparable concentrations. However, preliminary data show that siliceous mesoporous molecular sieves (MCM-41 and HMS) treated similarly with ammonium titanyl oxalate solutions exhibit good epoxidation activity. It is inferred that the presence of framework cations that can be extracted by oxalate species and/or the presence of defect sites in the parent zeolite is a requisite for the subsequent incorporation of titanium. 

Chemical precipitation is a popular method for synthesizing solid materials from solution in which a liquid-phase reaction is utilized to prepare insoluble compounds. The precipitates are composed of crystalline or amorphous fine particles. Usually, rare earth oxides are prepared by calcinations of the hydroxide or oxalate gel precipitated from a reaction of an aqueous or alcohol solution of inorganic salt (nitrate, chloride, sulfate, and ammonium nitrate, etc.) with an alkali solution (NaOH, NH4OH, and (NH2)2 H20) or an oxalic acid solution [15-21]. However, it is very difficult to obtain ultrafine particles because of growth and sintering of the particles during the calcinations. 

Procedure. A drop of the test solution (the P2O5 content should not exceed 0.1 mg) is mixed in a microcentrifuge tube with 2 drops of molybdate solution, and centrifuged. The supernatant liquid is transferred to a micro crucible by means of a capillary tube, and gently warmed. After cooling, 2 drops of 1 % oxalic acid solution are added to destroy any remaining traces of ammonium phosphomolybdate. A drop of benzidine and a few drops of saturated sodium acetate solution are then added. A blue color indicates silicic acid. 

Color development To 50.0 mL sample add in rapid succession 1.0 mL 1 + 1 HCl and 2.0 mL ammonium molybdate reagent. Mix by inverting at least six times and let stand for 5 to 10 min. Add 2.0 mL oxalic acid solution and mix thoroughly. Read color after 2 min but before 15 min, measuring time from addition of oxalic acid. Because the yellow color obeys Beer s law, measure photometrically or visually. 

The plant material is extracted by ethanol-benzene or chloroform-methanol to remove crude lipids cold/warm water to remove proteins and soluble carbohydrates ammonium oxalate-oxalic acid solution or aqueous ethylene-diamino-tetra-acetic acid-solution ( EDTA) to remove ->pectins acidic sodium chlorite to remove lignins. 

Stannous Oxalate. Stannous oxalate, Sn(C20 (mol wt 206.71, dec 280°C, sp gr 3.56 at 18°C), is a white crystalline powder, is soluble in hot concentrated hydrochloric acid and mixtures of oxaHc acid and ammonium oxalate, and is insoluble in water, toluene, ethyl acetate, dioctyl phthalate, THF, isomeric heptanes, and acetone (171). It is prepared by precipitation from a solution of stannous chloride and oxaHc acid and is stable indefinitely. 

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... 

A) Preparation of 4-Acetyl-7-Chloro-1,2,3,4-Tetrahydro-1-Methyl-5H-1,4-Bemodiazepin-5-one A mixture of 68.5 g (0.37 mol) of 5-chloro-N-methylanthranilic acid, 51 g (0.51 mol) of calcium carbonate, 76 g (0.37 mol) of bromoethylamine hydrobromide and 2.5 liters of water was stirred and heated under reflux for 3 hours. A solution of 23.4 g (0.26 mol) of anhydrous oxalic acid in 250 ml of water was slowly added to the refluxing mixture. The precipitated calcium oxalate was filtered off, and the filtrate adjusted to pH 7 with concentrated ammonium hydroxide. The filtrate was then concentrated to dryness in vacuo and the residue heated on the steam bath with 400 ml of 6 N ethanolic hydrogen chloride until the residue was crystalline. Filtration gave 122 g of N-(aminoethyl)-5-chloro-N-methylanthranilic acid hydrochloride as a solid. 

Determination of calcium as oxalate. Discussion. The calcium is precipitated as calcium oxalate CaC204,H20 by treating a hot hydrochloric acid solution with ammonium oxalate, and slowly neutralising with aqueous ammonia solution ... 

Heating the ore with sulfuric acid converts neodymium to its water soluble sulfate. The product mixture is treated with excess water to separate neodymium as soluble sulfate from the water-insoluble sulfates of other metals, as well as from other residues. If monazite is the starting material, thorium is separated from neodymium and other soluble rare earth sulfates by treating the solution with sodium pyrophosphate. This precipitates thorium pyrophosphate. Alternatively, thorium may be selectively precipitated as thorium hydroxide by partially neutralizing the solution with caustic soda at pH 3 to 4. The solution then is treated with ammonium oxalate to precipitate rare earth metals as their insoluble oxalates. The rare earth oxalates obtained are decomposed to oxides by calcining in the presence of air. Composition of individual oxides in such rare earth oxide mixture may vary with the source of ore and may contain neodymium oxide, as much as 18%. 

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