Acids species

Ionic species containing the characteristic cation - e.g. NH4CI - are acids species containing the characteristic anion are bases, e.g. KNH2. 

Ionisations 2, 3 and 5 are complete ionisations so that in water HCI and HNO3 are completely ionised and H2SO4 is completely ionised as a monobasic acid. Since this is so, all these acids in water really exist as the solvated proton known as the hydrogen ion, and as far as their acid properties are concerned they are the same conjugate acid species (with different conjugate bases). Such acids are termed strong acids or more correctly strong acids in water. (In ethanol as solvent, equilibria such as 1 would be the result for all the acids quoted above.) Ionisations 4 and 6 do not proceed to completion... 

The reaction proceeds until aU. available monomer has reacted or until it is terminated by an acidic species. The gel point in these m situ polymerizations, as represented by the time of fixture, occurs within several seconds on strongly catalytic surfaces such as thermoset mbbers to several minutes on noncatalytic surfaces. 

Meta.1 Conta.mina.nts and Ash. Alkali metals form basic oxides that are very reactive toward acidic species such as the acid gases, siHcates, and alurninates. These form stable salts with acid gases if the off-gas contains such gases. Sodium, the most common of these metals, prefers to form chlorides ahead of sulfates. Sodium carbonate only forms in the absence of haHdes and sulfur oxides, SO. There usually is too Htde NO present to form nitrates (see Sodium compounds). 

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

The use of neutralising amines in conjunction with an oxygen scavenger—metal passivator improves corrosion control in two ways. First, because any acidic species present is neutralized and pH is increased, the condensate becomes less corrosive. Second, most oxygen scavenger—passivators react more rapidly at the mildly alkaline conditions maintained by the amine than at lower pH levels. For these reasons, this combination treatment is gaining wide acceptance, particularly for the treatment of condensate systems that are contaminated by oxygen. 

As a result of the concentration of acidic species, such as chloride and sulfate, material scraped from the inside of tubercles is virtually always acidic when mixed with water. Acidity varies not only from tubercle to tubercle but also from place to place in a given tubercle. Acidity is greatest near the corroded metal surface. The size of the fluid-filled cavity can indicate acidity. The larger the cavity, the more acidic the internal environment. 

Deposits contained organic acids formed by oxidation of rolling oils. Up to 40% by weight of the lumps shown in Fig. 4.27A and B was iron oxides, hydroxides, and organic-acid iron salts. Acidic species concentrated in the deposits. 

In general, the higher the residual or applied metal stress, the more severe the corrosion at a given acidic pH. This explains why many heat exchanger tube ends are often attacked so severely (Fig. 7.1). Tube ends that have been rolled or welded often contain high residual stress. Further, crevices are sometimes present in which acidic species may concentrate (see Chap. 2, Crevice Corrosion ). Screens, rolled sheet metal, and other highly worked metals (not stress relieved) are also prone to attack. 

Arrhenius acid Species that, upon addition to water, increases [H+], 86 Arrhenius base Species that, upon addition to water, increases [OH-], 86 Arrhenius equation Equation that expresses the temperature dependence of the rate constant In k2/ki = a(l/Ti — 1 IT2)IR, 302-305... 

It must be noted that the cyclic model fails to account for the role of the additional alkyllithium and diethylaluminum that are required in precise amounts to achieve high selectivity. A simple model that recognizes a possible role for the additional reagents suggests the intermediacy of an extended, noncyclic transition state G with the aldchydic oxygen coordinated to some undefined Lewis acidic species derived from the additional components of the reaction mixture26,44. Aggregates composed of enolate, alkyllithium and dialkylaluminum species are also possible. 

High-boiling products found in this procedure and in similar experiments involving cyclohex-2-enone derivatives5 probably result from bimolecular reduction processes.15 3-Methylcyclohexanone, which arises by protonation rather than alkylation of the enolate (and which made up ca. 12% of the volatile products), is probably the result of reaction of allyl bromide with liquid ammonia to form the acidic species allyl ammonium bromide.5 10... 

This chapter also considers concentration variables that do not themselves necessarily play a role in the mechanism. For example, pH variations may affect the rate of a reaction because an acidic species (HA) is ionized (to A ). The size and direction of the pH effect depend in this instance on how either or both of these species enter the mechanism. Of course, in aqueous solution H+ and OH- may play direct roles as well. 

Sodium tungstate has also been used as a catalyst in the oxidation of dimethyl sulphoxide to the sulphone36. The kinetics of this reaction have been studied in great detail and it has been shown that oxygen transfer to the sulphoxide takes place via two peroxytungstic acid species (HW05 and HWOg ). 

Analysis of sulfonic acid species in sulfonated olefins. Kupfer and Kuenzler [108] reported the determination of acid species following partition between a 6.5% hydrochloric acid solution in 40% ethanol and a 1 1 (v/v) propan-2-ol-hexane mixture. The organic fraction contains alkenesulfonic and hydroxy-alkanesulfonic acids and the aqueous phase disulfonic acids and sulfato-sulfonates. The monosulfonic acids were converted to methyl esters and separated by column chromatography. To determine sulfatosulfonates the aqueous fraction was hydrolyzed and then partitioned and chromatographed. The separation is controlled using IR spectroscopy. 

Fig. 14-1 Extent of dissolution of phosphoric acid species as a function of pH in distilled and sea waters (Atlas, 1975).

Suzuki Y, Ito T, Suzuki T, HoUand RE Jr, Chambers TM, Kiso M, Ishida H, Kawaoka Y (2000) Sialic acid species as a determinant of the host range of influenza A viruses. J Virol 74 11825-11831... 

The concentrations of lactic acid and other organic acid species were determined by HPLC CTOlOA... 

There are several acidic species present in any solution of a polyprotic acid. The solution of carbonic acid in Example contains the following concentrations of acidic species ... 

To draw molecular pictures illustrating a proton transfer process, we must visualize the chemical reactions that occur, see what products result, then draw the resulting solution. When a strong base is added to a weak acid, hydroxide ions remove protons from the molecules of weak acid. When more than one acidic species is present, the stronger acid loses protons preferentially. 

The reduced catalyst deactivation compared to the analogous oxidations of glycerol and tartronic acid was attributed to the use of the calcium salt rather than the free acid. A recent publication describes a similar observation for the oxidation of sodium gluconate [15]. Sodium ions were assumed to counter catalyst deactivation by neutralizing the acid species responsible. 

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