Hydrofluoric acid composition

Corrosion inhibition is primarily associated with acidizing. Buffered hydrofluoric acid compositions have been shown to be less corrosive (147). Corrosion inhibitors are designed to reduce the rate of reaction of fluid with metal surfaces, generally by forming films on the surfaces. Acetylenic alcohols and amines are frequently components of corrosion inhibitor blends. Other compounds that have been used include nitrogen heterocyclics, substituted thioureas, thiophenols, and alpha-aminoalkyl thioethers (148). 

Hydrolysis of solutions of Ti(IV) salts leads to precipitation of a hydrated titanium dioxide. The composition and properties of this product depend critically on the precipitation conditions, including the reactant concentration, temperature, pH, and choice of the salt (46—49). At room temperature, a voluminous and gelatinous precipitate forms. This has been referred to as orthotitanic acid [20338-08-3] and has been represented by the nominal formula Ti02 2H20 (Ti(OH). The gelatinous precipitate either redissolves or peptizes to a colloidal suspension ia dilute hydrochloric or nitric acids. If the suspension is boiled, or if precipitation is from hot solutions, a less-hydrated oxide forms. This has been referred to as metatitanic acid [12026-28-7] nominal formula Ti02 H2O (TiO(OH)2). The latter precipitate is more difficult to dissolve ia acid and is only soluble ia concentrated sulfuric acid or hydrofluoric acid. 

Antimony(Ill) fluoride may be prepared by treating antimony trioxide or trichloride with hydrofluoric acid. Pure SbF is then obtained by carefully evaporating all of the water from the cmde product, which is subsequently sublimed. SbF does not hydrolyze as readily as do the other antimony ttihahdes. When heated in open air at 100°C, a crystalline soHd quickly forms of composition Sb302(0H)2F3, which, upon further heating, is transformed into antimony oxide fluoride [11083-22-0] SbOF. This compound may also be prepared by heating 1 1 mixtures of Sb203 and SbF. There are three known crystalline modifications. 

Alloy 400 Hydrofluoric acid Usually IG 1. Stress relieve after fabrication 2. Control composition of weld electrode/filler 3. Control residual O2 and other oxidising agents... 

Tantalum is severely attacked at ambient temperatures and up to about 100°C in aqueous atmospheric environments in the presence of fluorine and hydrofluoric acids. Flourine, hydrofluoric acid and fluoride salt solutions represent typical aggressive environments in which tantalum corrodes at ambient temperatures. Under exposure to these environments the protective TajOj oxide film is attacked and the metal is transformed from a passive to an active state. The corrosion mechanism of tantalum in these environments is mainly based on dissolution reactions to give fluoro complexes. The composition depends markedly on the conditions. The existence of oxidizing agents such as sulphur trioxide or peroxides in aqueous fluoride environments enhance the corrosion rate of tantalum owing to rapid formation of oxofluoro complexes. 

The furnace scales which form on alloy steels are thin, adherent, complex in composition, and more difficult to remove than scale from non-alloy steels. Several mixed acid pickles have been recommended for stainless steel, the type of pickle depending on the composition and thickness of the scale For lightly-scaled stainless steel, a nitric/hydrofluoric acid mixture is suitable, the ratio of the acids being varied to suit the type of scale. An increase in the ratio of hydrofluoric acid to nitric acid increases the whitening effect, but also increases the metal loss. Strict chemical control of this mixture is necessary, since it tends to pit the steel when the acid is nearing exhaustion. For heavy scale, two separate pickles are often used. The first conditions the scale and the second removes it. For example, a sulphuric/hydrochloric mixture is recommended as a scale conditioner on heavily scaled chromium steels, and a nitric/hydrochloric mixture for scale removal. A ferric sulphate/ hydrofluoric acid mixture has advantages over a nitric/hydrofluoric acid mixture in that the loss of metal is reduced and the pickling time is shorter, but strict chemical control of the bath is necessary. 

Stoneware and porcelain are attacked only by hydrofluoric acid and hot concentrated caustic alkalis and are almost completely unaffected by all concentrations of mineral and organic acids, acid salts and weak alkalis. The degree of susceptibility depends upon composition, firing temperature and porosity. 

The main advantages of the method can be formulated as follows. First, hydrofluoric acid is not needed for the decomposition stage the amount of fluorine required for the raw material decomposition can be calculated and adjusted as closely as possible to the stoichiometry of the interaction. Since the leaching of the fluorinated material is performed with water, a significant fraction of the impurities are precipitated in the form of insoluble compounds that can be separated from the solution, hence the filtrated solution is essentially purified. There is no doubt that solutions prepared in this way can be of consistent concentrations of tantalum and niobium, independent of the initial raw material composition. 

Kuterev, Stoyanov, Bagreev and Zolotov [461] reported on the investigation, using IR spectroscopy, of the composition of niobium and tantalum complexes extracted by amines from fluoride solutions. It was shown that in solutions that contain hydrofluoric acid in concentrations ranging from 1M to 12M, both niobium and tantalum were extracted in the form of NbF6 and TaF6 ... 

The unique advantage of the plasma chemical method is the ability to collect the condensate, which can be used for raw material decomposition or even liquid-liquid extraction processes. The condensate consists of a hydrofluoric acid solution, the concentration of which can be adjusted by controlling the heat exchanger temperature according to a binary diagram of the HF - H20 system [534]. For instance, at a temperature of 80-100°C, the condensate composition corresponds to a 30-33% wt. HF solution. 

Y. A. Balakirov, A. I. Chemorubashkin, G. A. Makeev, I. P. Korolev, and V. N. Glushchenko. Composition for treatment of stratum head zone—contains oxyethylated isononyl phenol, aqueous solution of hydrofluoric acid and aqueous solution of hydrochloric acid. Patent SU 1770555-A, 1992. 

The amphoteric agents exhibit excellent compatibility with inorganic electrolytes and with acids and alkalis. Such is their stability in strongly acidic solution that they are even used in cleaning compositions based on hydrofluoric acid [14]. 

The solution experiments may be made in aqueous media at around ambient temperatures, or in metallic or inorganic melts at high temperatures. Two main types of ambient temperature solution calorimeter are used adiabatic and isoperibol. While the adiabatic ones tend to be more accurate, they are quite complex instruments. Thus most solution calorimeters are of the isoperibol type [33]. The choice of solvent is obviously crucial and aqueous hydrofluoric acid or mixtures of HF and HC1 are often-used solvents in materials applications. Very precise enthalpies of solution, with uncertainties approaching 0.1% are obtained. The effect of dilution and of changes in solvent composition must be considered. Whereas low temperature solution calorimetry is well suited for hydrous phases, its ability to handle refractory oxides like A1203 and MgO is limited. 

In 1976, an X-ray powder diffraction analysis of a substance obtained from Te02, dissolved in concentrated hydrofluoric acid, was performed (96). The orthorhombic crystals had the composition H2Te203F4. The structure was shown to be characterized by... 

Partial substitution of fluorine for oxygen in VO2 and V 2O5 has been achieved by treating these oxides with aqueous hydrofluoric acid under pressure. The new phases of composition V02. xFjc (for 0 < x < 0.2) and V205 Fj( (for 0 < X < 0.025) were obtained and characterized by X-ray diffraction studies. The oxide-fluoride bronze K0.25VO0.75F2.25 has been prepared from the high-temperature reaction of KVO3 and VF3 and the unit cell parameters have been determined. 

Elemental composition Hf 84.80%, O 15.20%. Hafnium may be analyzed in aqueous solution following digestion with hydrofluoric acid-nitric acid, or with aqua regia. The dioxide may be characterized nondestructively by x-ray methods. 

Elemental composition Fe 59.51%, F 40.49%. The compound may he analyzed hy x-ray techniques. Iron may he analyzed hy AA or ICP/AES methods following digestion with dilute hydrofluoric acid and nitric acid and appropriate dilution. 

Elemental composition Mg 39.02%, F 60.98%. The compound is digested with nitric acid-hydrofluoric acid mixture, diluted and analyzed for magnesium by AA or ICP method. The crystals may be characterized nondestruc-tively by x-ray crystallography. 

Elemental composition Se 40.92%, F59.08%. The gas may be dissolved in nitric acid and dilute hydrofluoric acid and the solution appropriately diluted and analyzed for selenium (see Selenium). The hexafluoride may be decomposed with ammonia at 200°C and product selenium analyzed by AA, and gaseous products nitrogen and hydrogen fluoride diluted with helium and analyzed by GC-TCD or GC/MS. Alternatively, selenium hexafluoride diluted with helium is introduced onto the GC injector port and analyzed by GC/MS. Molecular ions have masses 194, 192, 196, and 190. 

Elemental composition Si 26.97%, F 73.03%. The gas is bubbled slowly through water to decompose into silicic acid and hydrofluoric acid. HE is analyzed for fluoride ion by fluoride-selective electrode or by ion chromatography. Silicon in the aqueous solution can be measured by AA or ICP. 

Elemental composition W 73.59%, H 0.81%, O 25.61%. The compound is dissolved in hydrofluoric acid and the solution diluted with water and analyzed for tungsten (See Tungsten). 

Table 4 shows the composition of aromatic hydrocarbons which have been obtained through dissolving used HZSM5 samples in hydrofluoric acid and... 

In carrying out the alkylation of benzene the propylene tetramer is reacted with an excess of benzene in the presence of a Friedel-Crafts catalyst such as aluminum chloride, boron trifluoride, or hydrofluoric acid. With careful control of this reaction, yields of alkylate boiling from 500° to 650° F. are of the order of 80% of theory with the losses due to slight olefin degradation and dialkylation. Inspection of commercial aromatic products, believed to be typical of this process, indicates the composition to be that shown in... 

A. A. Bineau9 found that during the boiling of a cone. aq. soln. of hydrofluoric acid an excess of hydrogen fluoride escapes until there remains a soln. with a constant b.p., 130°, and a constant composition corresponding with about 36 per cent. HF. In an analogous way, if dil. soln. are distilled, the first fractions are particularly rich in water, this continues until there remains an acid with the same constant b. temp, and the same constant composition. Similarly, if the cone, or dil. acid is allowed to stand over slaked lime, the former becomes more dil. and the latter more cone. 

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