Sulfuric acids, lead oxides

Certain of the above reactions are of practical importance. The oxidation of hydrogen sulfide in a flame is one means for producing the sulfur dioxide required for a sulfuric acid plant. Oxidation of hydrogen sulfide by sulfur dioxide is the basis of the Claus process for sulfur recovery. The Claus reaction can also take place under mil der conditions in the presence of water, which catalyzes the reaction. However, the oxidation of hydrogen sulfide by sulfur dioxide in water is a complex process leading to the formation of sulfur and polythionic acids, the mixture known as Wackenroeder s Hquid (105). 

The oxidation of octaethylporphyrin 418 with hydrogen peroxide in sulfuric acid leads under pinacol rearrangement to a mixture of hydroporphyrinones, among them the expected three constitutionally isomeric isobacteriochlorins. 

Oxidation of that compound with chromium trioxide in sulfuric acid leads cleanly to the desired ketone (67). Treatment with hydrobromic acid serves to demethylate the phenolic ether function (68). Direct... 

The oxidation of wood charcoal by means of sulfuric acid leads to mellitic acid and its decarboxylation products 6 nitric add may also be employed.7 Pyromellitic acid has also been obtained by the electrolytic oxidation of graphite in an alkaline medium.8... 

Zinc also may be produced by electrolysis of zinc sulfate solution. The zinc oxide in the roasted concentrate is leached with sulfuric acid. The oxide is converted to soluble zinc sulfate. Impurity metals, such as iron, copper, cadmium, arsenic, tin, and cobalt are removed by precipitation, floe formation, and other methods. The purified zinc sulfate solution is electrolyzed using aluminum cathodes and lead anodes. Zinc is deposited on the cathode. 

Process does not lead to the oxidation of nitrogen, or the degradation of sulfuric acid to oxides of sulfur, and no dioxins or furans are produced. 

The dibenzopyranone ring system may be viewed as a chromone with an additional fused benzene ring and thus generally related to the antiasthmatic mediator release inhibitor cromolyn (see Chapter 11). Two dibenzopyranones have in fact been investigated for this indication in the clinic. Friedel-Crafts cyclization of the substituted cresyloxybenzoic acid (2-1) in sulfuric acid leads to the dibenzopyranone (2-2). The methyl group is then oxidized to a carboxylic acid by means of chromic acid. The acid is then converted to its sodium salt, xanoxate sodium (2-3) [2]. 

Similarly sodium dichromate dihydrate in DMSO is a poor oxidant, but the addition of catalytic quantities of sulfuric acid leads to the effective oxidation of a variety of alcohols to give aldehydes and ketones in good yield (80-90%).Oxidations are normally complete within 90 min at 70 C, and may be performed in commercial DMSO without the need for further purification. 

SULFURIC ACID, INDIUM SALT see ICJOOO SULFURIC ACID, IRON(2- ) SALT (1 1) see FBNIOO SULFURIC ACID, IRON (3 SALT (3 2) see FBAOOO SULFURIC ACID, LEAD(2+) SALT (1 1) see LDYOOO SULFURIC ACID, MAGNESIUM SALT (1 1), compounded with 2,2 -DITHIOBIS(PYRIDINE) 1,T-OXIDE see OIU850... 

The nickel-cobalt sulfides as a suspension in dilute sulfuric acid are oxidized in agitated, spherical autoclaves at 350°F in the presence of air at 500 psig and excess sulfides. The unleached solids in the thickener overflow are recycled back to the autoclave and the liquor, containing 50 gm/liter Ni, 5 gm/liter Co as sulfates and small amounts of iron, aluminum, chromium, copper, zinc, and lead, is purified. The iron, aluminum, and chromium are precipitated as the hydroxides by adjusting the pH to 5.5 with ammonia and the copper, lead, and most of the zinc are removed by subsequent addition of sulfuric acid to lower the pH to 1.5 and precipitation of the metals with hydrogen sulfide. 

PbSO HjO S Pb Violent reaction with boric acid potassium. Reacts, possibly violently, with carbon dust, finely divided aluminum, magnesium, zirconium. High heat and fire decon osition products include toxic fumes of sulfur and lead oxides. Probable human carcinogen. On small fires, use dry chemical powder (such as Purple-K-Powder), foam, or COj extinguishers. 

Narcotine can be split into cotarnine and opianic acid by treatment with dilute sulfuric acid by oxidation with dilute nitric acid, chromic acid, potassium permanganate or with mercuric acetate (691). Hydrogenolysis (hydrochloric acid or sulfuric acid and zinc) affords hydrocotarnine and meconine. Treatment of hydrocotarnine with sodium in ethanol leads to cleavage of the methoxyl group with the formation of 8-hydroxy-1,2-dihydrohydrastinine. The phthalidetetrahydroisoquinoline alkaloids can be converted into rhoeadane see Section III,M and spirobenzylisoquinoline (see Section 111,0,1) precursors (692). 

In the lead chamber process for the manufacture of sulfuric acid, nitric oxide, oxygen (from the air), sulfur dioxide, and water (steam), interact. The nitric oxide acts as the catalyst, and is present at the end of the action, with the sulfuric acid. It acts as oxygen carrier. One of the intermediate compounds which is formed contains nitrogen peroxide (NO2), sulfur dioxide, and water. It may be obtained in crystalline form, known as chamber crystals which have the composition HSQ3NO2, nitro-sulfonic acid, under certain conditions. This substance is decomposed in the presence of an excess of steam or water vapor into sulfuric acid and nitric oxide, or better, nitrogen trioxide, N2O3. While the exact formulation of the intermediate compounds is not simple under the various conditions, the evidence at hand is sufficient to make the existence of at least one intermediate compound certain. 

The proposed mechanism for this methane oxidation is shown in Scheme 18.2 and follows steps discussed in more detail in the next section. One remarkable feature of this platinum system in this highly acidic medium at high temperatures is the thermodynamic stability of platinum(II) boimd by the bipyrimidine ligand. Addition of platinum metal to bipyrimidine in sulfuric acid leads to generation of the platinum(II) bipyrimidine complex (Equation 18.8). 

The first industrial catalyst was probably the niter pot, which was used in the early sulfuric acid lead chamber process when it became known that oxides of nitrogen catalyzed the oxidation of sulfur dioxide. How was this important process—on which chemical development soon depended—discovered Was it from the observation that cannons corroded or that condensation was acidic following the explosion of gunpowder All the ingredients for chamber acid were there—sulfur, saltpeter, atmospheric air, and heat. Ostwald noted that copious brown fumes were evolved as gunpowder exploded, but did not make any comment on sulfur oxides. Empirical observations, or inspired deductions, ditr-ing the 1800s led to the introduction of several more important catalytic processes. The inevitable development of a chemical industry based on the use of catalysts followed from a mass of experimental observations, such as those shown in Table 1.1, accumulated after Berzelius defined catalysts in 1835 (Figure 1.1). 

Acid Oxidation. Reactions of lead with acid and alkaUes are varied. Nitric acid, the best solvent for lead, forms lead nitrate acetic acid forms soluble lead acetate in the presence of oxygen sulfuric acid forms insoluble lead sulfate. Sulfuric acid is stored in containers with chemical or acid-grade lead. Lead dissolves slowly in HCl, but in the presence of aqueous alkaUes forms soluble plumbites and plumbates. 

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