Problems Sulphuric acid

M.p. I08-5 C. Ordinary DDT contains about 15% of the 2,4 -isomer, and is prepared from chloral, chlorobenzene and sulphuric acid. It is non-phytotoxic to most plants. It is a powerful and persistent insecticide, used most effectively to control mosquitoes in countries where malaria is a problem. It is stored in the bodies of animals and birds. 

Reconcentration of sulphuric acid A very large amount of tantalum heater surface has been installed in plants for the reconcentration of diluted sulphuric acid arising from metal pickling, oil refinery operations and from petrochemical processes producing alcohols and ketones. Since reconcentration provides a means of overcoming a waste of disposal problem, the use of such plants is expanding ... 

Fig. 10,54 Potentiostatic anodic polarisation curves for mild steel in 10% sulphuric acid. Note the magnitude of the critical current density which is lO -lO A/m this creates a problem in practical anodic protection since very high currents are required to exceed icu. and therefore...

In addition a number of the species involved may be solvated giving rise to the alternative equilibria (57a) etc., so that clearly to unravel the nature of the appropriate reacting species, the sequence in which they are involved, and the ratedetermining step is a formidable kinetic task. It is therefore not surprising that the number of mechanisms proposed, and the number of papers published on the subject, has tended to be comparable. The problem is heightened by the fact that there is a relatively large number of species present in sulphuric acid to consider, and any equilibrium which produces a molecule of water then requires a further molecule of sulphuric acid to ionise the water via the equilibrium ... 

A very wide range of substituent effects have also been measured using acetic acid (4 vol.) and aqueous sulphuric acid (3 vol.), the rate coefficients for the corresponding strengths of the added sulphuric acid being given in Table 232 (refs. 537, 673, 679-685). It will be noted that the rate coefficients do not always increase with an increase in the strength of the sulphuric acid (as stated) and this arises from the same reason noted above except that the problem becomes more... 

Traditionally, aromatic nitrations have been performed with mixtures of concentrated nitric and sulphuric acids leading to considerable effluent problems associated with the spent acid. A heterogeneous alternative for. sulphuric acid has been reported (Bertea et al., 1995), namely dealuminated Mordenite, which is sufficiently robust to be able to catalyse the vapour-phase nitration of benzene with 65% aqueous nitric acid. 

Dinkevich F.E., Juravel T.A., Ksenzhek O.S. and Lobach G.A. The Solubility of Some Quinon Compounds in the Sulphuric Acid Solvents. (Rus.), Problems of Chemistry and Chemical Technology IVoprosy Khimii i Khimicheskoy Tekhnologiil (Ukrainian Journal). 1979 55 10-12. 

Beckmann rearrangement of oxime is an acid catalysed reaction. The environmental problems associated with the use of sulphuric acid instigated interest to use number of solid acid catalysts [1], There are only scanty references about Lewis acid ion-exchanged MeAlPOs. Beyer et al. [2], Mihalyi et al. [3] and Mavrodinova et al. [4] already suggested the presence of Lewis acid metal ions as MO+ species in zeolites. The present study focussed the synthesis and characterisation of Fe3+, La3+ and Ce3+ ion-exchanged MAPO-36. The catalytic results of Beckmann rearrangement of cyclohexanone oxime over ion-exchanged catalysts are delineated in this article. 

The work on the electrochemical generation of a solution of ceric sulphate from slurry of cerous sulphate in 1-2 M sulphuric acid was abandoned by BCR due to difficulties encountered in handling slurried reactants. A 6kW pilot reactor operated at 50 °C using a Ti plate anode and a tungsten wire cathode (electrolyte velocity about 2ms 1) produced 0.5 M Ce(S04)2 on the anode with a current efficiency of 60%. The usefulness of Ce(IV) has been limited by the counter anions [131,132], Problems include instability to oxidation, reactivity with organic substrates and low solubility. Grace found that use of cerium salts of methane sulfonate avoids the above problems. Walsh has summarized the process history, Scheme 6 [133],... 

Downstream from the 3rd bed, the gas is cooled and passed to an intermediate absorption tower, in which the S03 formed is absorbed in recirculating sulphuric acid. The cold and practically S03-free process gas is reheated to 380-440°C and returned to the converter, where the remaining SO2 is converted to S03 in a 4th catalyst bed. The rest of the S03 is subsequently recovered in a final absorption tower before the process gas, containing a small fraction of unconverted S02, is emitted through the stack. The combustion air is dried with the 98 wt% product acid in order to avoid corrosion and acid mist problems in the plant. The sulphuric acid process normally operates close to atmospheric pressure with the combustion air blower dimensioned just for compensation of the pressure drop through the plant. 

The fate of alkyl cations in proton acid systems has been well investigated, especially in sulphuric acid. The ability to vary continuously the acidity of this solvent and study the fate of alkyl cations as a function of acidity has provided insight into the problem. 

Preparative scale reduction of nitramines and nitrosamines in acid solution is a convenient route to substituted hydrazines. Early workers used a cathode of tinned copper [120], More recently mercury has been employed as cathode material, although tin would probably be equally suitable. Nitrosamines are conveniently reduced in dilute hydrochloric acid and evaporation of the electrolyte at the end of the reaction affords the hydrazine hydrochloride [121]. Some nitroso compounds are unstable to these acidic conditions. In the case of N-nitrosoindoles, this problem has been overcome in an ingenious manner [122]. The nitroso compound and aqueous sulphuric acid are mixed just prior to reaction and then forced through a porous cathode of bronze coated with mercury at such a rate that the reduction is completed in one pass through the cathode. Other workers have overcome the instability of N-benzyl-N-nitrosoanthraniiic acid towards acid by working in an acetate buffer at below room temperature [123],... 

Faga, A., Scevola, D., Mezzetti, M.G., Scevola, S. Sulphuric acid burned women in Bangladesh a social and medical problem. Bums 26, 701-709 (2000)... 

The nitrous sulphuric acid is decomposed, but comparatively slowly, when subjected to the action of sulphurous acid in an undiluted state - and. this appears tohavo been the cause of the failure in the commencement, inasmuch as the acid flowed from the decomposer almost of the same density as when introduced. It would seem inconsistent that the expedient of mixing it with water so as to dilute it was not adopted, especially as the decomposing action of water per se must have been observed. Doubtless this would have solved the problem, especially as with this addition a modification of his apparatus answers very well. 

The problem of how to stabilize nitrostarch has been solved by different means, but the majority of stabilization processes remain obscure as patent secrets. None the less, from certain observation some general conclusions can be made. It was early observed by Bechamp [13] that nitrostarch obtained by nitration in nitric acid alone is more stable than one obtained by means of nitric acid mixed with sulphuric acid. This has been confirmed experimentally by Hackel and T. Urbanski [18], and seems likely to be explained by the formation of starch sulphates or mixed nitric and sulphuric esters of starch. 

The main disadvantage of mercury sensors based on bare gold layers is their poor selectivity. This is illustrated in Fig. 12.6 an incubation at 100% humidity (Fig. 12.6a), with saturated vapour of sulphuric acid (Fig. 12.6), volatile sulphides or thiols (10 pg/1 of 1-butanethiol vapour, Fig. 12.6c), or halogens (10 pg/1 of iodine vapour, Fig. 12.6d), results in conductivity changes of the same magnitude as an incubation with 10-20 ng/1 of mercury vapour. This interference with widely spread substances is a serious problem in applications of such sensors for real probes and makes necessary a pre-treatment of probes. 

The formation of the nitrosonium ion follows the acidity function HR and the conversion of nitrous acid to nitrosonium bisulphate is essentially complete in ca. 65% sulphuric acid. At these high acidities, there is no reason to doubt that the nitrosonium ion is the effective electrophile. The problem arises with studies at lower acidities for most of the kinetic evidence for equation (19) relates to feebly acidic media. 

In order to illustrate this problem, it is interesting to analize the unsubstituted polyamides prepared from aliphatic diamines and aromatic diacids or from aliphatic diamines and aliphatic diacids. They are only soluble in solvents such as sulphuric acid, trifluoracetic acid, m-cresol, etc. 

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