Sulfuric acid system

Chemical Properties. The chemistry of sodium metabisulfite is essentially that of the sulfite—bisulfite—metabisulfite—sulfurous acid system. The relative proportions of each species depend on the pH. The pH of a sodium bisulfite solution obtained by dissolving 10 wt % sodium metabisulfite in water at 20°C is 4.9 at 30 wt %, the pH is 4.4. 

H. Lennartz and co-workers. Vaporisation Equilibrium of the Water—Sulfuric Acid System, Rep. Fur. 6783, Commission of European Communities, Hydrogen Energy Vector, Europe, 1980, pp. 60—70. 

These alloys have extensive applications in sulfuric acid systems. Because of their increased nickefand molybdenum contents they are more tolerant of chloride-ion contamination than standard stainless steels. The nickel content decreases the risk of stress-corrosion cracking molybdenum improves resistance to crevice corrosion and pitting. 

Replacing some of the nickel with iron produces a family of alltws with intermediate corrosion resistance between stainless steels and the Ni-Cr-Mo alloys. Alloys such as Incoloy 825 and Hastelloy G-3 and G-30 are in this family. Incoloy 825 has 40 percent Ni, 21 percent Cr, 3 percent Mo, and 2.25 percent Cu. Hastelloy G-3 contains 44 percent Ni, 22 percent Cr, 6.5 percent Mo, and 0.05 percent C maximum. These alloys have extensive applications in sulfuric acid systems. Because of their increased nickel and molybdenum contents they are more tolerant of chloride-ion contamination than are standard stainless steels. The nickel content decreases the risk of stress-corrosion cracking molybdenum improves resistance to crevice corrosion and pitting. Many of the nickel-based alloys are proprietary and are coverecf by the following specifications ... 

Sulfite-bisulfite-metabisulfite-sulfurous acid system, 23 672 Sulfite ester, 23 651 Sulfite lignins, 75 15-18 Sulfite oxidation kLaL measurement method, 75 679... 

The preparation of l-amino-4-nitrosonaphthalene is given here by way of an illustration of the technique used in this reaction. 1-Aminonaphthalene has been withdrawn from the market because of its suspected tumor-producing characteristics and therefore this example is not to be considered an illustration of a safe reaction. It hardly needs to be emphasized that, quite generally, due precautions must be taken when working with the indicated concentrated sulfuric acid system. In carrying out this reaction, a large excess of nitrosation reagent must be avoided to reduce the possibility of diazotization of the primary amine. 

Direct nitration of compounds (20) and (22) are straightforward reactions, with preferential electrophilic substitution occurring at C-3. The nitration proceeded in yields of approximately 50% using a mixed nitric/sulfuric acid system <70JHC373>. 

Acid Exchange in Specific Heterocyclic Compounds The sulfuric acid system has been the most extensively studied and will be used to demonstrate the application of the method in determining the reactivity of heterocyclic compounds to deuterium and/or tritium labeling. A summary of representative data with the other acidic catalysts for labeling heterocyclic compounds will complete this section. 

Hgurc 4.14 (a) A typical phase diagram for a poly (p-phenylene terephthala-mide)-sulfuric acid system, a solution that is used to make Kevlar fiber (after Kikuchi, 1982). (b) Viscosity versus polymer concentration in PPTA/HjSO solution. Note the sharp drop in viscosity at about 20% which corresponds to a transition between isotropic and nematic liquid crystal phase. 

Heart alkymer from storage and 100% sulfuric acid from the sulfuric acid system (which can be represented by a block) are pumped... 

The first acids of the sulfuric acid system to be recognized (29) were disulfuric acid, H2S2O7, and the higher polysulfuric acids, H2SSO10 etc., which are present in oleum. Dilute oleum contains mainly disulfuric acid, H2S2O7, and from cryoscopic measurements on such solutions the first dissociation constant of disulfuric acid has been found to be 1.4 X 10 2 (5). It is approximately 30% ionized in a 0.1 m solution ... 

B, 1, c), although the extent to which this occurs varies widely from one element to another. Thus, for example, the oxides and hydroxides of the more electropositive metals are completely converted into the corresponding hydrogen sulfates, while phosphoric acid, for example, is merely pro-tonated and undergoes no conversion into a sulfato derivative. In general a wide variety of compounds intermediate between the oxides and hydroxides of the aqueous system and the sulfates and hydrogen sulfates of the sulfuric acid system may be formed. Some of the possible compounds and the relations between them are illustrated in Fig. 5 for the... 

Addition of a synergist to the DEFIPA/FICI extraction system such as tributylphosphate (TBP) has a two-sided effect in improving extraction at high acidity and hindering extraction at low acidity. At low acidity, as in the analogous sulfuric acid system, the presence of TBP disrupts the creation of polymeric complexes between and DEFIPA. ... 

The purpose of this study was to investigate the anionic exchange behavior of neptunium(V) in sulfate-sulfuric acid, because neptunium is often present as a contaminant during the separation of other actinides (l ). Sulfuric acid systems are seldom utilized in industrial processes, but are often used as part of a laboratory analytical procedure. Literature on neptunium in HC101, HC1, HC1-HF, and HNO3 is quite complete, but the information on the H2S0l system is sketchy at best. There is one report 2) that neptunium(V) is adsorbed strongly on Dowex 2 resin from 0.1 IT to 1 IT H SOip Our measurements indicate that there is very little adsorption of Np(V) on Dowex 1 resin even at low concentrations of sulfate-sulfuric acid. We believe the differences in chemical structure of the two resins are not sufficient to explain the disparity in adsorption. 

In addition to catalysis of small molecule transformations and biocatalysis, non-functionalized LLC phases used as reaction media have also been found to accelerate polymerization reactions as well. For example, the L and Hi phases of the sodium dodecylsulfate/n-pentanol/sulfuric acid system have been found to lower the electric potential needed to electropolymerize aniline to form the conducting polymer, polyaniline [110]. In this system, it was also found that the catalytic efficiency of the L phase was superior to that of the Hi phase. In addition to this work, the Ii, Hi, Qi, and L phases of non-charged Brij surfactants (i.e., oligo(ethylene oxide)-alkyl ether surfactants) have been observed to accelerate the rate of photo-initiated radical polymerization of acrylate monomers dissolved in the hydrophobic domains [111, 112]. The extent of polymerization rate acceleration was found to depend on the geometry of the LLC phase in these systems. Collectively, this body of work on catalysis with non-functionalized LLC phases indicates that LLC phase geometry and system composition have a large influence on reaction rate. 

FIGURE 10.14 Vapor pressure of sulfuric acid as a function of temperature using the Ayers et al. (1980) and Kulmala and Laaksonen (1990) estimates. (Reprinted with permission from Kulmala, M. and Laaksonen, A. Binary nucleation of water sulfuric acid system. Comparison of classical theories with different H2S04 saturation vapor pressure, J. Chem. Phys. 93, 696-701. Copyright 1990 American Institute of Physics.)... 

Kulmala, M., and Laaksonen, A. (1990) Binary nucleation of water sulfuric acid system. Comparison of classical theories with different H2SO4 saturation vapor pressures, J. Chem. Phys. 93,696-701. 

The aqueous sulfuric acid system is highly complex with varying concentrations of H20, H2SC>4, HSO, SO4-, and H3SO4 less is known about other aqueous acids. The ability of X and XH+ to respond to varying modes of interaction with these species can scarcely be expected to be neatly related to a single interaction such as XH+--0H2 and the above results show clearly that they cannot. 

Although the presence of solvate phases has been established and qualitative phase diagrams have been published, to our knowledge, a detailed model for a pol3nner solvate and its phase behavior has not been presented. At this time we would like to present a partial phase diagram for the poly(p-phenylene terephthalamide) (PPTA)/sulfuric acid system and a model for the crystal solvate formed. In addition the structure of a model complex will be described. 

Differential Scanning Calorimetry (DSC) of the PPTA/ sulfuric acid system was carried out in order to establish the melting behavior of the system. Samples (5-10 mg) were sealed in gold-coated aluminum pans under N, and cooled at 10 C/min to -150 C. Subsequently the samples were heated to 100 C at 10 C/min and the melting thermograms were recorded. 

---