Oxalic acid as reagent

Oxalacetic acid esters s. a-Keto-/5-dicarboxylic acid esters Oxalic acid as reagent 16, 253... 

The method of anion exchange chromatography for heavy metal analysis may also be applied to ion-pair chromatography. With oxalic acid as the complexing agent and tetrabutylammonium hydroxide as the ion-pair reagent, an elution order opposite to cation analysis is obtained. The separation of anionic metal complexes on MPIC phases... 

Figure 9.4 shows an alternative oxide production stage using the fairly expensive oxalic acid as a process reagent. A pure product is, however, obtained, as a fine, free flowing powder. Calcium reduction of the oxide to metal powder, as selected for Fig. 9.4., is used on a commercial scale and gives a very satisfactory product. 

A separation of eleven cations with indirect non-suppressed-conductivity detection is illustrated in Figure 7.18. The mobile phase contained both a strong acid (MSA) and oxalic acid as a complexing reagent [16]. The peaks actually denote decreasing conductivity. 

Redox titrants (mainly in acetic acid) are bromine, iodine monochloride, chlorine dioxide, iodine (for Karl Fischer reagent based on a methanolic solution of iodine and S02 with pyridine, and the alternatives, methyl-Cellosolve instead of methanol, or sodium acetate instead of pyridine (see pp. 204-205), and other oxidants, mostly compounds of metals of high valency such as potassium permanganate, chromic acid, lead(IV) or mercury(II) acetate or cerium(IV) salts reductants include sodium dithionate, pyrocatechol and oxalic acid, and compounds of metals at low valency such as iron(II) perchlorate, tin(II) chloride, vanadyl acetate, arsenic(IV) or titanium(III) chloride and chromium(II) chloride. 

Multiple products are possible from C02 hydrogenation, but all of the products are entropically disfavored compared to C02 and H2 (Scheme 17.1). As a result, the reactions must be driven by enthalpy, which explains why formic acid is usually prepared in the presence of a base or another reagent with which formic acid has an exothermic reaction. Of the many reduction products that are theoretically possible, including formic acid, formates, formamides, oxalic acid, methanol, CO, and methane, only formic acid and its derivatives are readily prepared by homogeneous catalysis. 

The highest concentrate grade and PGM recoveries were achieved using a mixture of oxalic acid and thiourea. The use of Q1SO4 as an activator was examined in relation to the point of addition and type of depressant used [11]. It was concluded that the point of reagent addition played an important role in PGM recovery. 

The 2,3-dioxo-6-thioxo-2,3,5,6-tetrahydro-l/7-imidazo[l,2-A]pyrazole 393 and 5,6-dioxo-2,3-dihydro-l//-imidazo[l,2- ]-imidazole 395 were synthesized by condensation of the respective 5-amino-3-thioxo-2,3-dihydro-pyrazole 392 and 2-aminoimidazoline 394 compounds with either oxalyl dichloride or diethyl oxalate in moderate to poor yields (Equations 178 and 179) <1995JPR472, 2002EJM845>. These cyclizations can suffer from various side reactions such as expulsion of CO, polymerization, or formation of open-chain products. To solve these problems, reagents such as oxalic acid bis-imidoyl- and bis-hydrazoylchlorides 397 and 400 as well as 2,3-dichloroquinoxalines 403... 

It is evident that other methods end reagents may be adopted. For example, the original solution In aqua regia may be concentrated by evaporation, until it is very much reduced in quentlty then add about throe-fourths of its bulk of spirit of wine, and, lastly, a saturated solution of chloride of ammonium. By these reagents the platinum will be thrown down as a yellow Crystalline precipitate, while the solution filtered from this, and treated with sulphate of iron or boiled with oxalic acid, deposits geld. 

---