Aqueous solution acidic solutions

Frequently we need more oxygen or hydrogen to complete the mass balance for a reaction or half-reaction in aqueous solution. We must be careful, however, not to introduce other changes in oxidation number or to use species that could not actually be present in the solution. We cannot add H2 or O2 to equations because these species are not present in aqueous solutions. Acidic solutions do not contain significant concentrations of OH ions. Basic solutions do not contain significant concentrations of H+ ions. 

Anhydrous cupric sulphate is white but forms a blue hydrate and a blue aqueous solution. The solution turns yellow when treated with concentrated hydrochloric acid, dark blue with ammonia, and gives a white precipitate and brown solution when treated with potassium iodide. A yellow-brown aqueous solution of ferric chloride becomes paler on acidification with sulphuric or nitric... 

An alternative procedure for the above test is as follows. Mix 2-3 ml. of 2 per cent, aqueous paraperiodic acid solution with 1 drop of dilute sulphuric acid (ca. 2 5N) and add 20-30 mg. of the compound. Shake the mixture for 5 minutes, and then pass sulphur dioxide through the solution until it acquires a pale yellow colour (to remove the excess of periodic acid and also iodic acid formed in the reaction). Add 1-2 ml. of Schiff s reagent (Section 111,70) the production of a violet colour constitutes a positive test. 

Even the bulk permittivities of aqueous sulphuric acid solutions are unknown. 

Oxalic acid, H2C2O4, (aqueous) Dilute acid solution. Ag, Au, Cu, Hg, La, Ni, Pb, rare... 

Processes for Triacetate. There are both batch and continuous process for triacetate. Many of the considerations and support faciUties for producing acetate apply to triacetate however, no acetyl hydrolysis is required. In the batch triacetate sulfuric acid process, however, a sulfate hydrolysis step (or desulfonation) is necessary. This is carried out by slow addition of a dilute aqueous acetic acid solution containing sodium or magnesium acetate (44,45) or triethanolamine (46) to neutrali2e the Hberated sulfuric acid. The cellulose triacetate product has a combined acetic acid content of 61.5%. 

Ammonium fluorohafnate [1692 -24-9], (NH4)2HfFg, or potassium fluorohafnate [16871 -86-6], K HfF, can be prepared by crystallisation from an aqueous hydrofluoric acid solution by addition of ammonium fluoride or potassium fluoride, respectively. 

The dihydrate is soluble ia water. The specific gravities of aqueous oxaUc acid solutions are summarized ia Table 2. The solubiUty of the dihydrate ia water iacreases with temperature. Approximate solubiUty values (5) are given by the foUowiag formulas, where S = g(COOH)2/100 g soln and t = ° C. 

Group 17 (VIIA) Perchlorates. Fluorine perchlorate [37366 8-6] FCIO, is formed by action of elemental fluorine and 60—70% aqueous perchloric acid solution (68). The compound is normally a gas. It melts at —167.5° C and boils at — 15.9°C. It is extremely reactive and explosive ia all states. 

Aqueous sulfamic acid solutions are quite stable at room temperature. At higher temperatures, however, acidic solutions and the ammonium salt hydroly2e to sulfates. Rates increase rapidly with temperature elevation, lower pH, and increased concentrations. These hydrolysis reactions are exothermic. Concentrated solutions heated in closed containers or in vessels having adequate venting can generate sufficient internal pressure to cause container mpture. An ammonium sulfamate, 60 wt % aqueous solution exhibits mnaway hydrolysis when heated to 200°C at pH 5 or to 130°C at pH 2. The danger is minimised in a weU-vented container, however, because the 60 wt % solution boils at 107°C (8,10). Hydrolysis reactions are ... 

Donation of a proton to the reactant often forms a carbenium ion or an oxonium ion, which then reacts ia the catalytic cycle. For example, a catalytic cycle suggested for the conversion of phenol and acetone iato bisphenol A, which is an important monomer used to manufacture epoxy resias and polycarbonates, ia an aqueous mineral acid solution is shown ia Figure 1 (10). 

Dilute aqueous hypochlorous acid solutions are quite stable if pure, especially if kept cool and in the dark. For example, at 0°C the decomposition rate of a 1 M solution is only about 0.3%/d. At 20°C the decomposition rate is about tenfold higher. Decomposition produces oxygen, chloric acid, and chlorine. 

Table 3. pH and Specific Gravity of Aqueous Citric Acid Solutions... 

The absorbate containing the mixed ethyl sulfates is hydroly2ed with enough water to give an approximately 50—60% aqueous sulfuric acid solution. The hydrolysis mixture is separated in a stripping column to give dilute sulfuric acid bottoms and a gaseous alcohol—ether—water mixture overhead. The overhead mixture is washed with water or dilute sodium hydroxide and then purified by distillation (63,65,66,68,69). 

Total Pressure, bar, of Aqueous Sulfuric Acid Solutions, , , , 2-83... 

TABLE 2-12 Water Partial Pressure, bar, over Aqueous Sulfuric Acid Solutions Concluded)... 

BrCl can be prepared by the reaction in the gas phase or in aqueous hydrochloric acid solution. In the laboratory, BrCl is prepared by oxidizing bromide salt in a solution containing hydrochloric acid. 

The largest protonated cluster of water molecules yet definitively characterized is the discrete unit lHi306l formed serendipitously when the cage compound [(CyHin)3(NH)2Cll Cl was crystallized from a 10% aqueous hydrochloric acid solution. The structure of the cage cation is shown in Fig. 14.14 and the unit cell contains 4 [C9H,8)3(NH)2aiCUHnOfiiai- The hydrated proton features a short. symmetrical O-H-0 bond at the centre of symmetry und 4 longer unsymmetrical O-H - 0 bonds to 4... 

Aqueous perchloric acid solutions exhibit very little oxidizing power at room temperature, presumably because of kinetic activation barriers, though some strongly reducing species slowly react, e.g, Sn , Ti , V and V , and dithion-ite. Others do not, e.g. H2S, SO2, HNO2, HI and, surprisingly, Cr and Eu . Electropositive metals dissolve with liberation of H2 and oxides of less basic metals also yield perchlorates, e.g. with 12% acid ... 

The mixture is refluxed with stirring for ten hours, cooled and filtered. The filtrate is extracted three timas with 200 cc portions of 6 N acetic acid. The aqueous acetic acid solution is then made strongly basic with 10% sodium hydroxide solution, and extracted three times with 200 cc portions of ether. The ether extract is dried with anhydrous sodium sulfate, stirred with 5 g of activated carbon and filtered to provide 2-[p-chloro-a(2-di-methylaminoethoxylbenzyll pyridine in solution. Addition of a solution of 116 g (1 mol) of maleic acid in 1,500 cc of ether gives 323 g (79%) of solid which, on recrystallization from ethyl acetate, gives white solid 2-[p-chloro-a(2-dimethvlaminoethoxv)benzyl] pyridine maleate melting at 117° to 119°C. 

A mixture of 31 5 g (0.1 mol) of 2-chloro-9-(3 -dimethylaminopropylidene)-thiaxanthene (MP 97°C) and 100 g of N-( 3-hydroxyethyl)-piperazine is heated to 130°C and boiled under reflux at this temperature for 48 hours. After cooling, the excess of N-( 3-hydroxyethyl)-piperazine Is evaporated in vacuo, and the residue is dissolved in ether. The ether phase is washed with water and extracted with dilute acetic acid, and 2-chloro-9-[3 -N-(N - -hydroxy-ethyD-piperazinylpropylidene] -thiaxanthene separated from the aqueous acetic acid solution by addition of dilute sodium hydroxide solution to basic reaction. The free base is extracted with ether, the ether phase dried over potassium carbonate, the ether evaporated and the residue dissolved in absolute ethanol. By complete neutralization of the ethanolic solution with a solution of dry hydrogen chloride in absolute ethanol, the dihydrochloride of 2-chloro-9-[3 -N-(N -(3-hydroxyethyl)-piperazinylpropylidene] -thiaxanthene is produced and crystallizes out as a white substance melting at about 250°C to 260°C with decomposition. The yield is 32 g. 

Preparation of 2-Hydroxy-4,4 -Dicyanostilbene 10 grams of 2-amino-4,4 -dicyanostilbene thus prepared were dissolved in 400 cc of boiling glacial acetic acid and 200 cc of dilute sulfuric acid added the solution was suddenly chilled and diazotized over one and a half hours at 5° to 10°C with sodium nitrate (3.0 grams/15 cc H O). The diazonium salt solution was decomposed by boiling for 15 minutes with 600 cc of 55% aqueous sulfuric acid solution the solution was diluted, cooled and filtered. The residue crystallized from ethyl alcohol as lemon yellow prismatic needles, MP 296°C. 

A mixture of 10.0 g of 3-methylsulfinyl phenothiazine (MP 193° to 195°C), 6.1 g of finely powdered sodium hydroxide and 125 cc of toluene is boiled for 1 hour under reflux with a water separator on an oil bath kept at a temperature of 150°C, while the mixture is stirred. Without interrupting the boil a solution of 7.0 g of 2-(N-methvl-piperidyl-2 )-1-chloroethane (BP 84°C/10 mm Hg) in 10 cc of toluene is added dropwise in the course of 1 hour, after which boiling is continued for another 3 hours. When the reaction mixture has cooled it is first washed with 25 cc of water three times and then extracted with 75 cc of a 15% aqueous tartaric acid solution. The tartaric acid extract is shaken out with 25 cc... 

The residue was then heated at about 90°C for 16 hours on a steam bath with 300 cc of 20% aqueous hydrochloric acid solution, and treated with a small amount, e.g., 1 gram of charcoal. The hydrochloric acid was then removed under a vacuum of 15 mm, the residue dissolved in 30 cc of water and precipitated by the addition of 2.4 cc of concentrated aqueous ammonia. The precipitate was filtered off and dried. It consists of M-hydroxydihydro-normorphinone. It is soluble in ethanol. 

The combined liquors, which comprise an aqueous hydrochloric acid solution of 3-amino-methyl-pyridine hydrochloride, are then heated to a temperature of 60° to 65°C, and ethyl nitrite gas is passed into the heated solution. The ethyl nitrite is generated by placing 20 liters of 90% ethyl alcohol in a suitable vessel, diluting with 200 liters of water, and, while stirring, adding to the dilute alcohol 18.3 kg of nitrosyl chloride at the rate of 2.25 kg per hour. (The process using methyl nitrite is carried out by substituting a stoichiometrically equivalent quantity of methyl alcohol for the ethyl alcohol.)... 

After termination of the reaction by adding 200 ml of a 25% aqueous acetic acid solution, the reaction mixture was mixed with 5 liters of cold acetone to precipitate the reaction product. The precipitate was collected by filtration, washed with acetone, and dissolved in 500 ml of distilled water. The resulting aqueous solution was immediately adjusted to pH 6.0 and poured into a column containing 2 liters of CM-Sephadex C-25 (NH type) packed in 0.05 M aqueous ammonium chloride solution to adsorb bleomycins. 

Ethyl-2-methyl-3-(10,11) -dihydro-5H-dibenzo [a,d] cycloheptene-5-ylidene)-1 -pyrrolinium iodide (4.7 g) was dissolved in 7 cc of methanol. To this solution there were added 1.4 g of sodium boron hydride within about 80 minutes with stirring and stirring of the solution was continued for two hours to complete the reaction. The reaction mixture was acidified with 10% aqueous hydrochloric acid solution and then the methanol was distilled off. The residual solution was alkalized with 20% aqueous sodium hydroxide solution and extracted with ether. The ether layer was dried over magnesium sulfate and the ether was distilled off. The resulting residue was further distilled under reduced pressure to yield 2.0 g of 1-ethyl-2-methyl-3-(10,11 ) dihydro-5H-dibenzo[a,d]cycloheptene-5-ylidene)pyrrolidine (boiling point 167°C/4 mm Hg.). 

The undistilled aqueous tartaric acid solution was extracted with three 1-liter portions of ethyiene dichloride, and was then brought to a pH of about 8.5 to 9.5 by the addition of 28% aqueous ammonium hydroxide. The ammoniacal solution was extracted with three 1-liter portions of ethylene dichloride the ethylene dichloride extracts were combined, were dried, and were evaporated in vacuo, yielding a residue of 3.35 grams of a iight-brown powder. 

Isobutylene oxide is produced in a way similar to propylene oxide and butylene oxide by a chlorohydrination route followed by reaction with Ca(OH)2. Direct catalytic liquid-phase oxidation using stoichiometric amounts of thallium acetate catalyst in aqueous acetic acid solution has been reported. An isobutylene oxide yield of 82% could be obtained. 

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