Perchloric acid solution

Group 17 (VIIA) Perchlorates. Fluorine perchlorate [37366 8-6] FCIO, is formed by action of elemental fluorine and 60—70% aqueous perchloric acid solution (68). The compound is normally a gas. It melts at —167.5° C and boils at — 15.9°C. It is extremely reactive and explosive ia all states. 

Extremely high purity ammonium perchlorate can be made by the direct reaction of ammonia and pure perchloric acid solution (8,36) ... 

Chemical Designations - Synonyms Dioxonium perchlorate solution Perchloric acid solution Chemical Formula HCIO4-H2O. 

This procedure can now be repeated with a base D that is slightly weaker than C, using C as the reference. In this stepwise manner, a series of p determinations can be made over the acidity range from dilute aqueous solution to highly concentrated mineral acids. Table 8-18 gives pS bh+ values determined in this way for nitroaniline bases in sulfuric and perchloric acid solutions. This technique of determining weak base acidity constants is called the overlap method, and the series of p kBH+ values is said to be anchored to the first member of the series, which means that all of the members of the series possess the same standard state, namely, the hypothetical ideal 1 M solution in water. 

X is an acidity function based on the first-order approximation, Eq. (8-92). Values of X have been assigned by an iterative procedure. The data consist of values of Cb/cbh+ as functions of Ch+ for a large number of indicators. For each indicator an initial estimate of pXbh+ and m is made and X is calculated with Eq. (8-94). This yields a large body of X values, which are fitted to a polynomial in acid concentration. From this fitted curve smoothed X values are obtained, and Eq. (8-94), a linear function in X. allows refined values of pXbh + and m to be obtained. This procedure continues until the parameters undergo no further change. Table 8-20 gives X values for sulfuric and perchloric acid solutions. ... 

Values of X for Aqueous Sulfuric and Perchloric Acid Solutions... 

Aqueous perchloric acid solutions exhibit very little oxidizing power at room temperature, presumably because of kinetic activation barriers, though some strongly reducing species slowly react, e.g, Sn , Ti , V and V , and dithion-ite. Others do not, e.g. H2S, SO2, HNO2, HI and, surprisingly, Cr and Eu . Electropositive metals dissolve with liberation of H2 and oxides of less basic metals also yield perchlorates, e.g. with 12% acid ... 

Hydrolysis of the acetate ester with alkali, e.g., sodium methoxide in methanol, affords the free alcohol, 16/3-methyl-1,4,9( 11 )-pregnatriene-17o, 21-diol-3,20-dione. To a suspension of 3 grams of 16/3-methyl-1,4,9(11)-pregnatriene-17o,21-diol-3,20-dione-21-acetate in 40 ml of acetone is added at 0°C with stirring 2 grams of N-chlorosuccinimide and then 7 ml of a perchloric acid solution prepared by dissolving 0.548 ml of 70% perchloric acid in 33 ml of water. The resulting reaction mixture is stirred at 0°C for about 4 hours 45 minutes. 

Table 21.16 Exchange current densities for several noble metals and a platinum-rhodium alloy in the reduction of oxygen from perchloric acid solution ...

Notes. (1) All solutions should be freshly prepared before use. Perchloric acid solutions must not be exposed to sunlight or elevated temperatures as they can be EXPLOSIVE. 

The standard or formal potential of ferroin can be modified considerably by the introduction of various substituents in the 1,10-phenanthroline nucleus. The most important substituted ferroin is 5-nitro-l,10-phenanthroline iron(II) sulphate (nitroferroin) and 4,7-dimethyl-1,10-phenanthroline iron(II) sulphate (dimethylferroin). The former (E° = 1.25 volts) is especially suitable for titrations using Ce(IV) in nitric or perchloric acid solution where the formal potential of the oxidant is high. The 4,7-dimethylferroin has a sufficiently low formal potential ( e = 0.88 volt) to render it useful for the titration of Fe(II) with dichromate in 0.5 JVf sulphuric acid. 

The temperature behavior of low446,491,503 558 as well as high Miller index crystal faces of Au447,448 has been examined in 0.01 M perchloric acid solutions. For all gold surfaces studied, C, was found to decrease and Ea=Q moved to less negative values with increasing t 446-448 491503-558... 

Vittori O (1980) Polarographie study of adsorbed tellurium at the hanging and dropping mercury electrodes in 1 M hydrochloric or perchloric acid solutions. Anal Chim Acta 121 315-319... 

By means of a stopped-flow technique, Carlyle and Espenson ° ° have subjected the reaction between europium(II) and iron(III) to a detailed examination. In perchloric acid solution two processes are discerned, viz. 

The reduction of Co(lll) by Fe(II) in perchloric acid solution proceeds at a rate which is just accessible to conventional spectrophotometric measurements. At 2 °C in 1 M acid with [Co(IlI)] = [Fe(II)] 5 x 10 M the half-life is of the order of 4 sec. Kinetic data were obtained by sampling the reactant solution for unreacted Fe(Il) at various times. To achieve this, aliquots of the reaction mixture were run into a quenching solution made up of ammoniacal 2,2 -bipyridine, and the absorbance of the Fe(bipy)3 complex measured at 522 m/i. Absorbancies of Fe(III) and Co(lll) hydroxides and Co(bipy)3 are negligible at this wavelength. With the reactant concentrations equal, plots of l/[Fe(Il)] versus time are accurately linear (over a sixty-fold range of concentrations), showing the reaction to be second order, viz. 

Mercury(II) oxidises Cr(II) in aqueous perchloric acid solutions according to the stoichiometric equation... 

A slow reaction takes place between Hg(II) and Fe(ll) in perchloric acid solution viz. 

In dilute perchloric acid solution the reaction between Hg(ll) and Sn(II) is complete within 1 min for reactant concentrations of 10 M. After a detailed consideration, Wetton and Higginson conclude that a two-equivalent primary reaction is likely. 

The reaction between Tl(III) and U(IV) is one of the few redox reactions which have been studied in a mixed solvent. Solutions were kept under nitrogen. There are striking differences between the rate in aqueous perchloric acid and methanol-aqueous perchloric acid solutions. In the latter media the order with respect to Tl(III), U(IV), and H alters as the solvent composition is changed (Table 29). For 25% methanol-75 % water solvent the kinetic orders of 1.0, 1.5 and —1.33 with respect to U(IV), Tl(III), and H, respectively, are consistent with the existence of two competing pathr whose net activation processes are... 

This oxidation state is stable only when complexed by anions, e.g. PO4 , or in moderately acidic solutions. Perchloric acid solutions of Mn(IIl) perchlorate have been prepared these are fairly stable, although the omnipresent equilibrium... 

Further convincing evidence was found by Catherino - for the formation of arsenic(IV) during the electro-oxidation of arsenic(III) in perchloric acid solution. 

FIGURE 15.5 Polarization curves for anodic oxygen evolution at a platinum electrode in perchloric acid solutions with various concentrations (1) 1.34 (2) 3 (3) 5 (4) 9.8 M. 

Dederichs, F., Friedrich, K F. and Daum, W. (2000) Sum-frequency vibrational spectroscopy of CO adsorption on Pt(l 11) and Pt(llO) electrode surfaces in perchloric acid solution effects of thin-layer electrolytes in spectro-electrochemistry. J. Phys. Chem. B, 104, 6626-6632. 

Schmidt TJ, Grgur BN, Behm RJ, Markovic NM, Ross PN. 2000b. Bi adsorption on Pt(l 11) in perchloric acid solution A rotating ring-disk electrode and XPS smdy. Phys Chem Chem Phys 2 4379-4386. 

Grgur BN, Markovic NM, Ross PN. 1997. Underpotential deposition of lead on Pt(lll) in perchloric acid solution RRDpt(in)E measurements. Langmuir 13 6370-6374. 

El-Aziz AM, Kihler LA. 2002. New information about the electrochemical behaviour of Ru(OOOl) in perchloric acid solutions. Electrochem Commun 4 866. 

Garcia-Araez N, Climent V, Herrero E, Feliu J, Lipkowski J. 2006. Thermodynamic approach to the double layer capacity of a Pt(lll) electrode in perchloric acid solutions. Electrochim Acta 51 3787. 

Markovic NM, Adzic RR, Cahan BD, Yeager EB. 1994. Structural effects in electrocatalysis— Oxygen reduction on platinum low-index single-crystal surfaces in perchloric-acid solutions. J Electroanal Chem 377 249-259. 

Sun SG, Cai WB, Wan LJ, Osawa M. 1999. Infrared absorption enhancement for CO adsorbed on Au films in perchloric acid solutions and effects of surface structure studied by cyclic voltammetry, scanning tunneling microscopy, and surface-enhanced IR spectroscopy. J Phys Chem B 103 2460-2466. 

At more positive potentials, processes occur that depend on the composition of the electrolyte, such as the formation of H2S2Og and HS05 in sulphuric acid solutions, while the CIO radical is formed in perchloric acid solutions, decomposing to form C102 and 02. The formation of ozone has been observed at high current densities in solutions of rather concentrated acids. 

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