Sulphuric acid conductivity

Hence the strength of the acid goes up as sulphur trioxide is dissolved in it. The acidity of pure and fuming sulphuric acids is not so apparent as in ordinary aqueous acids because it is masked by the oxidising and other properties moreover, the conductivity... 

Solutions of nitric acid in 100% sulphuric acid have a high electrical conductivity. If nitric acid is converted into a cation in these solutions, then the migration of nitric acid to the cathode should be observed in electrolysis. This has been demonstrated to occur in oleum and, less conclusively, in concentrated acid, observations consistent with the formation of the nitronium ion, or the mono- or di-protonated forms of nitric acid. Conductimetric measurements confirm the quantitative conversion of nitric acid into nitronium ion in sulphuric acid. ... 

High-silicon irons may be used at elevated temperatures if the process requires it. For example, 20-in diameter (0-5m) pipe has been used for acid concentrations handling boiling 95% sulphuric acid at approximately 285°C where the products of combustion reach temperatures of the order of 590°C. The principal limitation on their use is imposed by their relatively low thermal conductivities and susceptibility to cracking from thermal shock this demands that the rate of application or removal of heat should not be rapid. 

An increase in conductivity usually increases T because it increases the proportion of polarisation in the total cell potential difference and lowers the ratio ( V A )/( V - AEj). Changing the conductivity of an acid copper bath with sulphuric acid produced the following result (291 A/m average c.d., P = 5) ... 

The existence of materials now included among the conducting polymers has long been known. The first electrochemical syntheses and their characterization as insoluble systems took place well over a century ago. In 1862 Letheby reported the anodic oxidation of aniline in a solution of diluted sulphuric acid, and that the blue-black, shiny powder deposited on a platinum electrode was insoluble in HjO, alcohol, and other organic solvents. Further experiments, including analytical studies, led Goppelsroeder to postulate in 1876 that oligomers were formed by the oxidation of aniline. 

In 1968 DairOlio et al. published the first report of analogous electrosyntheses in other systems. They had observed the formation of brittle, filmlike pyrrole black on a Pt-electrode during the anodic oxidation of pyrrole in dilute sulphuric acid. Conductivity measurements carried out on the isolated solid state materials gave a value of 8 Scm . In addition, a strong ESR signal was evidence of a high number of unpaired spins. Earlier, in 1961, H. Lund had reported — in a virtually unobtainable publication — that PPy can be produced by electrochemical polymerization. 

When reporting the molar conductivity data, the species whose amount is given in moles should be indicated. Often, a fractional molar conductivity corresponding to one mole of chemical equivalents (called a val) is reported. For example, for sulphuric acid, the concentration c can be expressed as the normality , i.e. the species H2S04 is considered. Obviously, A(H2S04) = 2A( H2S04). Consequently, the concept of the equivalent conductivity is often used, defined by the relationship... 

Recent studies performed with deactivated anodes show [55] that electroless or electrolytic platinum deposition on failed anodes, not only lowered the polarisation behaviour of these anodes (see Fig. 5.20), but also demonstrated an equivalent lifetime as that of a new anode in accelerated life tests in the sulphuric acid solution (see Fig. 5.21). These results unequivocally demonstrate that the deactivation of anodes, for which the Ru loading is still high, is a direct consequence of the depletion of Ru from the outer region of the anode coating. Note that this process of surface enrichment by conducting electroactive species will not lead to reactivating a failed anode, if there is a TiC>2 build-up at the Ti substrate/coating interface. 

Because of the nature of the reaction by which molecules dissociate into ions there is not always a simple relationship between the increase in conductivity with increasing molar concentration and often a limiting value is reached. For instance, increasing concentrations of sulphuric acid result in increased conductivity up to a concentration of about 35% (v/v), above which the conductivity decreases. 

Typically, the electrodes are of lead dioxide on a titanium substrate in the form of horizontal perforated plates, usually 5-40 mm apart, depending on the conductivity of the liquid. A potential difference of 5-10 V may be applied to give current densities of the order of 100 A/m2. Frequently, the conductivity of the suspension itself is adequate, though it may be necessary to add ionic materials, such as sodium chloride or sulphuric acid. Electrode fouling can usually be prevented by periodically reversing the polarity of the electrodes. Occasionally, consumable iron or aluminium anodes may be used because the ions released into the suspension may then assist flocculation of the suspended solids. 

The new compounds M3[Nb(02)2F4],nH20 and M3[Ta(02)2F4],nH20 (M = NH4, n = 0 M = K or Na, n = 1) have been prepared, and i.r. and conductivity studies suggest that they involve eight-co-ordinate metal atoms. The stability constants of the niobium(v)-peroxide complexes formed in sulphuric acid solutions have been determined. ... 

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