Oxalic acid effect

The residue was dissolved in MeOH (20 cm ) and added slowly, with stirring, to a solution of anh. Oxalic acid (5.40g, 60mmol) in MeOH. Complete precipitation was effected by adding Et O (50 cm ) to the mixture and cooling it to -2(fC."... 

In acidic solution, the degradation results in the formation of furfural, furfuryl alcohol, 2-furoic acid, 3-hydroxyfurfural, furoin, 2-methyl-3,8-dihydroxychroman, ethylglyoxal, and several condensation products (36). Many metals, especially copper, cataly2e the oxidation of L-ascorbic acid. Oxalic acid and copper form a chelate complex which prevents the ascorbic acid-copper-complex formation and therefore oxalic acid inhibits effectively the oxidation of L-ascorbic acid. L-Ascorbic acid can also be stabilized with metaphosphoric acid, amino acids, 8-hydroxyquinoline, glycols, sugars, and trichloracetic acid (38). Another catalytic reaction which accounts for loss of L-ascorbic acid occurs with enzymes, eg, L-ascorbic acid oxidase, a copper protein-containing enzyme. 

Oxalic acid Beneficial reduces effects of CO2, salt water, dilute acetic acid... 

Meyers has demonstrated that chiral oxazolines derived from valine or rert-leucine are also effective auxiliaries for asymmetric additions to naphthalene. These chiral oxazolines (39 and 40) are more readily available than the methoxymethyl substituted compounds (3) described above but provide comparable yields and stereoselectivities in the tandem alkylation reactions. For example, addition of -butyllithium to naphthyl oxazoline 39 followed by treatment of the resulting anion with iodomethane afforded 41 in 99% yield as a 99 1 mixture of diastereomers. The identical transformation of valine derived substrate 40 led to a 97% yield of 42 with 94% de. As described above, sequential treatment of the oxazoline products 41 and 42 with MeOTf, NaBKi and aqueous oxalic acid afforded aldehydes 43 in > 98% ee and 90% ee, respectively. These experiments demonstrate that a chelating (methoxymethyl) group is not necessary for reactions to proceed with high asymmetric induction. 

Figure 8 Effect of acid concentration on the grafting of cotton linters. [KMn04] = 0.06 N [monomer] = 1 mol/g cell liquor ratio 1 50 T = 50°C t = 1 h. (—) Oxalic acid (----) sulfuric acid.

Molybdenum tends to be protected by vanadium in aerated 7 1 % hydrochloric acid and it receives a high degree of protection when coupled with copper in this medium. Molybdenum corrodes somewhat faster than normal in 3 1 % nitric acid when coupled with tungsten. It is not affected by contact with titanium in 3-1% nitric acid. It is protected by aluminium and copper in aerated 10% formic acid and by aluminium in air-aerated 9% oxalic acid. In the latter solution, copper had only a slight protective effect when coupled with molybdenum. 

On the other hand, the provision of vast numbers of minute nuclei assists the phosphate coating reaction to start at a multitude of centres, resulting in a finely crystalline coating. This effect can be obtained chemically by a predip in a solution of sodium phosphate containing minutely dispersed traces of titanium or zirconium salts or in weak solution of oxalic acid. This type of pre-dip entirely eliminates any coarsening effect due to previous treatment in strong alkalis or acids. 

C17-0116. Oxalic acid, a diprotic carboxylic acid found in many plants, including rhubarb, is an effective stain remover. Consider the following diagram to be a small section of an aqueous solution of oxalic acid ... 

The oxidation of oxalic acid by mercuric chloride to give CO2 and mercurous chloride is a classic example of an induced reaction. This reaction is extremely slow unless small quantities of chromic acid and manganous ions are added, whereon facile reduction takes place Addition of permanganate or persulphate and some reducing agents is also effective and the oxidation proceeds readily under photo- or X-irradiation (Eder s reaction). The large quantum yield points to a chain mechanism , which could also function with an inducing oxidant, viz. 

Calcium tartronate was precipitated and hence samples required acidification prior to the filtration step necessary to remove the catalyst. The chief product of over-oxidation was oxalic acid. However, conversion to oxalic acid proceeds at a relatively low rate and yields of the former are consequently high. This is probably partly due to the tartronate being precipitated, effectively hindering further oxidation. 

The effect of an aqueous solution of sodium chlorite on oxalic acid in the presence of sunlight gives rise to a violent detonation, which is supposedly due to the formation of chlorine dioxide that is unstable ... 

Smirnova NW, Petrii OA, Grzejdziak A. 1988. Effect of ad-atoms on the electro-oxidation of ethylene glycol and oxalic acid on platinized platinum. J Electroanal Chem 251 73-87. 

There is no reason why the technique cannot be applied to extract wave functions for larger systems. Calculations have recently been completed in our group on the oxalic acid dihydrate system in this case, hydrogen bonding effects were examined in detail. 

It may not be that surprising that an effective homogeneous catalyst for the reaction shown by Eq. (4) has not been found it is difficult to imagine a facile mechanism by which oxalate anion or oxalic acid could be generated at a metal center. 

Figure 18.8 Effect of level of oxalic acid/thiourea mixture on the PGM grade-recovery relationship (oxide PGM ore from Brazil).

Effect of level of oxalic acid on pyrochlore metallurgical results... 

The performance of oxalic acid was related to pH. The effect of pH on the grade-recovery relationship is shown in Figure 23.11. 

Figure 23.11 Effect of pH on Ta/Nb on the grade-recovery relationship using 800 g/t oxalic acid.

Limited research work has been conducted on these ores, but have indicated that REO cannot be recovered using either fatty acid or sodium oleate. It was, however, found that a mixture of sulphosuccinamate and phosphate ester modified with alkylsulphate can recover REO and zircon efficiently. Figure 24.5 shows the effect of above collector mixture (KBX3) on REO recovery from complex RE0-Zr02 ores. Oxalic acid and fatty acid (FA3) were not so effective compared to collector KBX3. 

It was shown that with the use of sulphonate collectors, sodium oxalate had a positive effect on monazite grade and recovery. Conditioning time with oxalate had a pronounced effect on monazite recovery. Figure 24.9 shows the effect of conditioning time with oxalic acid on monazite recovery. 

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