Hydrofluoric Acid HF

Like hydrochloric acid, anhydrous hydrofluoric acid is gaseous. It is highly soluble in water. 

This is the halogen acid that attacks aluminium most. In an acid at a concentration of 40%, the dissolution rate is 0.5 mm-h at room temperature. In anhydrous acid, the dissolution rate is low, in the order of 0.02 mm per year. 

Tests at — 10 °C have shown that the dissolution rate depends on the acid concentration and on the alloy. 5056 is particularly sensitive as the acid concentration decreases [4] (Table E.5.2). 

The very low dissolution rate of aluminium in concentrated hydrofluoric acid is due to the fact that AIF3 resulting from the reaction of aluminium with hydrofluoric acid 

Is it nevertheless possible to store and transport anhydrous hydrofluoric acid in aluminium vessels The same remark as for anhydrous hydrochloric acid applies to hydrofluoric acid. 

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Other kinds of liquid-liquid equilibria are encountered in processes such as alkylation, where anhydrous hydrofluoric acid (HF) is partially soluble in hydrocarbons. 

A large oil refinery had a failure in their alkylation unit resulting in a significant release of hydrofluoric acid (HF). This incident and others in refineries during recent years prompted members of the hydrocarbon processors to turn to HAZOP to better understand their risks. 

Precipitation of fluoride compounds from solutions of hydrofluoric acid, HF, is performed by the addition of certain soluble compounds to solutions containing niobium or tantalum. Initial solutions can be prepared by dissolving metals or oxides of tantalum or niobium in HF solution. Naturally, a higher concentration of HF leads to a higher dissolution rate, but it is recommended to use a commercial 40-48% HF acid. A 70% HF solution is also available, but it is usually heavily contaminated by H2SiF6 and other impurities, and the handling of such solutions is extremely dangerous. 

Preparation of the solutions was similar to that of niobium-containing solutions, i.e. by dissolving tantalum metal powder in hydrofluoric acid, HF, at a concentration of about 40% weight. 

Two types of digestion solutions are usually used for the chemical decomposition of the raw material hydrofluoric acid, HF, or a mixture of hydrofluoric and sulfuric acids, HF and H2SO4 [32], The process is performed using solutions with relatively high acid concentrations, at elevated temperatures and under intensive stirring for several hours to ensure effective digestion. The raw material is nearly completely dissolved. 

C) for cast iron and up to 140 °F for marstenitic SS (60 °C). It is widely used where silicates are present with the iron oxides. Typically, 5 to 7.5% HC1 is employed. The ammonium bifluoride normally is present at 0.5%, but it may be increased to a maximum of 1.5% for a boiler that has not been cleaned for many years. The presence of hydrofluoric acid (HF), which is formed by the reaction of ammonium bifluoride with HC1 (see equation), tends to increase the rate of iron oxide dissolution and reduce the corrosion rate of exposed steel, when compared to using HC1 alone. This is due to the stability of the hexafluoroferric ion (FeFg3 ), which prevents the ferric ion from corroding exposed steel. 

The LAB production process (process 1) is mainly developed and licensed by UOP. The N-paraffins are partially converted to internal /z-olefins by a catalytic dehydrogenation. The resulting mixture of /z-paraffins and n-olefins is selectively hydrogenated to reduce diolefins and then fed into an alkylation reactor, together with an excess benzene and with concentrated hydrofluoric acid (HF) which acts as the catalyst in a Friedel-Crafts reaction. In successive sections of the plant the HF, benzene, and unconverted /z-paraffins are recovered and recycled to the previous reaction stages. In the final stage of distillation, the LAB is separated from the heavy alkylates. 

Hydrofluoric acid, HF, is considered a weak acid. Which microscopic representation best Uiustrates this concept ... 

Although the total content of carbohydrate fractions of the three components is similar, as reported by Williams et al., 1990, it was found that protein-rich fractions have a significantly lower glucuronic acid content. Circular dichroism studies conducted on different GA fractions showed that only the AGP and GP components have a secondary structure (Renard et al., 2006). The AGP fraction was isolated by gel filtration chromatography and subjected to deglycosylation with hydrofluoric acid (HF) to separate the protein (Qi et al., 1991). About 400 amino acids were contained by the AGP protein fraction ( 33% are... 

C16-0105. Write the equilibrium reaction and equilibrium constant expression for each of the following processes (a) Trimethylamine, (CH3)3 N, a weak base, is added to water, (b) Hydrofluoric acid, HF, a weak acid, is added to water, (c) Solid calcium sulfate, CaSOq, a sparingly soluble salt, is added to water. 

In a solution of hydrofluoric acid, HF molecules donate protons to water molecules, generating H3 O and F" ions. As discussed in Chapter 16, the forward reaction and the reverse reaction must occur at equal rates in a solution that is at equilibrium. In an aqueous solution of HF that is at equilibrium, hydronium ions donate protons to fluoride ions to generate molecules of H2 O and HF ... 

Traditionally, the production of LABs has been practiced commercially using either Lewis acid catalysts, or liquid hydrofluoric acid (HF).2 The HF catalysis typically gives 2-phenylalkane selectivities of only 17-18%. More recently, UOP/CEPSA have announced the DetalR process for LAB production that is reported to employ a solid acid catalyst.3 Within the same time frame, a number of papers and patents have been published describing LAB synthesis using a range of solid acid (sterically constrained) catalysts, including acidic clays,4 sulfated oxides,5 plus a variety of acidic zeolite structures.6"9 Many of these solid acids provide improved 2-phenylalkane selectivities. 

Figure 6.3.1 The molecular structure of fluorosilicic acid, produced by the action of hydrofluoric acid (HF) on glass.

The etching of glass, Si02, by hydrofluoric acid, HF, is not an oxidation-reduction reaction, since no element in the reaction is undergoing a change in oxidation number. 

Consider hydrofluoric acid, HF, reacting with water HF + H20 H30+ + F-... 

Hydroelectric turbines, virtual two-way SMA devices in, 22 349-350 Hydroentanglement, 17 507-508 Hydrofinishing, 15 216 Hydroflumethiazide, molecular formula and structure, 5 162t Hydrofluoric acid (HF), 4 579t. See also Hydrogen fluoride North American capacity of, 14 15t production of, 14 15 silicon solubility in, 22 491-492 in sodium fluoride manufacture, 22 825 solubility of boron halides in, 4 140t solubility of metal fluoroborates in, 4 152t... 

Newer and more complex humus extractions have been developed. These typically involve more steps such as both physical separation on the basis of density and particle size (related to the size of soil inorganic components), and chemical separation based on extractions and washings with hydrofluoric acid (HF), hydrochloric acid (HC1), and sodium hydroxide (NaOH). The products of such separations are then subjected to spectroscopic analysis and interpretation [22,23],... 

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