Showing papers on "Hydrofluoric acid published in 1983"

Structure of liquid hydrogen fluoride studied by infrared and Raman spectroscopy

Abstract: Infrared and Raman spectra of hydrogen fluoride, deuterium fluoride, and their isotopic mixtures at various temperatures from 293 to 77 K have been recorded and analyzed in comparison with calculated data obtained from the classical G.F. matrix method applied to hypothetical structures chosen a priori. The best fit lead to the most probable structure of HF at 293 K which is a zig–zag chain with six or seven molecules having an angle of 42° with the average axis. At a lower temperature (190 K), just before solidification, the chains become longer, n=8 with an angle θ≂35 °. These structures fit well with the high dielectric constant of liquid hydrogen fluoride and lead to a calculated Kirkwood factor g1=3.65 at 293 K and g1=5.36 at 190 K which are in perfect agreement with known experimental values.

FTIR observation of the N2‐‐‐HF complex in solid argon

Abstract: Sharp absorptions at 3881.5 and 262 cm−1 in argon matrices containing HF are shown to depend upon N2. Substitution with DF indicates assignments to the νs and νl modes of the linear N2‐‐‐HF complex.

Method of fracturing a subterranean formation

Abstract: A method for fracturing a subterranean formation whereby undesirable fines are removed from the fracture face and/or proppant pack. The method is carried out by introducing hydrogen ions and fluoride ions into the formation being fractured and allowing hydrofluoric acid to be formed which dissolves the undesirable fines.

Stabilization of aqueous solutions containing hydrogen peroxide, hydrofluoric acid and metal ions

Abstract: Process for improving the stability of aqueous solutions containing hydrogen peroxide, metal ions and hydrofluoric acid which can be partially in the form of salts, comprising adding to the said solution at least one hydroxide selected from alkali metal hydroxides, ammonium hydroxide, or mixtures thereof in an amount which is insufficient to neutralize all the acidity present. The resultant novel stabilized solutions according to the invention are used in the surface treatment of metals especially of stainless steels.

Method of polishing glass articles in an acid bath

Abstract: The method according to the invention of polishing glass in a polishing bath containing sulfuric acid and hydrofluoric acid permits long polishing times and thus reduced alternating treatments in polishing bath and washing bath at high polishing speed due to the fact that the polishing bath contains at least one acid which is stronger than the hydrofluoric acid, in particular acids whose dissociation constants are higher than that of the second dissociation stage of the sulfuric acid; preferably, oxalic acid is used. In order that the sulfuric acid concentration can be increased--in particular for glasses containing alkaline earth--0.1 to 5 g sodium chloride and/or potassium chloride per liter of polishing bath are added to the polishing bath during an 8-hour shift, either all at once or in portions.

Indentification of the gas-phase trimer methyl sulfide-hydrofluoric acid complex [Me2S.cntdot.(HF)2] by photoelectron spectroscopy

Abstract: L'analyse du spectre de photoelectron UV du complexe (CH 3 ) 2 S•HF indique la presence d'une espece trimere (CH 3 ) 2 •(HF) 2 . Des calculs d'orbitales moleculaires montrent que (CH 3 ) 2 S•HF a une geometrie a l'equilibre non plane de symetrie C S

Process for acidic pickling of stainless steels and acidic solution for its use

Abstract: Process for acidic pickling of stainless steels, in which the acidic solution according to the invention, employed for its use, comprises essentially an acid whose anion is a complexant for ferric ions, for example hydrofluoric acid, and a strong oxidising agent capable of oxidising ferrous ions to ferric ions, such as aqueous hydrogen peroxide, which may be introduced directly or by means of a persalt. The method makes it possible to eliminate toxic gas releases and to envisage an easier processing of the spent baths.

Etching of chemically vapour-deposited amorphous Si3N4-C composites in HF solution

Abstract: Amorphous Si3N4-C[Am.CVD-(Si3N4] composites (C: 0.6 to 6 wt%) were prepared by chemical vapour deposition (CVD) using SiCl4, H2, NH3and C3H8 gases, and their etching characteristics in 47% hydrofluoric acid (HF) solution were investigated in the temperature range of 25 to 50° C. It was found that the etching rate decreases with increasing carbon content. The etching rate of the Am.CVD-(Si3N4-C) composite containing 6 wt% carbon was about 1/40 of the rate for carbon free Am.CVD-Si3N4. The activation energies obtained from the temperature dependence of the etching rates were 11 to 17 kcal mol−1, which increased with increasing carbon content. This paper also presents the study on the characteristics of the etched surfaces as well as the carbon state in the Am.CVD-(Si3N4-C) composites, and finally the possible etching mechanism is discussed.

Solid-State Structures of The Binary Fluorides of The Transition Metals

Abstract: Publisher Summary This chapter discusses the solid-state structures of the binary fluorides of the transition metals. There has been a great deal of interest in binary transition metal fluorides, over many years, both from the synthetic and structural points of view. Synthetically, this group of compounds has provided a challenge, ranging as it does from compounds that can be prepared from aqueous solution to those requiring either very sophisticated or very extreme techniques. Thus manganese difluoride can be separated from aqueous hydrofluoric acid solution, whereas the recently characterized gold pentafluoride was synthesized through the intermediate formation of dioxygenyl hexafluoroaurate, which was decomposed thermally under controlled conditions. Chromium hexafluoride and osmium heptafluoride are forrned only under conditions of high temperature and high excess pressure of fluorine, and can be isolated only by rapid quenching to liquid nitrogen temperatures.

Kinetics of the reaction between hydrofluoric acid and calcium oxide for fluoride emission control

Abstract: Basic kinetic data are presented for the reaction between HF and CaO where CaF2 is the reaction product. Two CaO materials were studied a reagent-grade CaO and calcined Greer limestone. The reaction is first order with respect to HF, and the intrinsic rate constants, k,, have been measured for temperatures ranging from 550 to 800 \"C. The diffusion coefficients of HF in CaF2 are also reported for this temperature range. With limestone or for the reaction system limestone-potlining-air, fusion of the products occurs a t temperatures above 790 \"C, caused by the eutectic complex NaCa2FSiOl. An example of possible application of this reaction in HF emission control is the combustion of potlining produced in aluminum industry in a fluidized bed combustor.

Upgrading of natural gasoline with trifluoromethane sulfonic acid, hydrofluoric acid and Lewis acid catalyst

Abstract: Natural gasoline of low octane value derived from natural gas is upgraded to higher octane value by means of a liquid ternary catalyst comprising trifluoromethanesulfonic acid and hydrogen fluoride in conjunction with a Lewis acid of the formula MX n wherein M is selected from Group III-A, IV-B or V elements of the Periodic Table, x is a halogen and n is a number varying from 3 to 6. Effective upgrading is achieved when the Lewis acid:HF mole ratio of the catalyst ranges from 1:2 to 2:1 at temperatures less than about 120° C. under liquid phase conditions.

Production of anhydrous hydrogen fluoride from low-grade metallic fluorides and sulfuric acid

Abstract: A novel method is provided for the production of anhydrous hydrofluoric acid from low-grade metallic fluorides using an intermediate aluminum fluoride compound. The method involves the reaction of low-grade metallic fluorides such as fluorspar with sulfuric acid to produce weak hydrofluoric acid. The weak acid is then reacted with a metallic salt (such as aluminum chloride) to form precipitated aluminum fluoride (AlF3.3H2 O). After dewatering, the aluminum fluoride is reacted with strong sulfuric acid to form aluminum sulfate and strong hydrofluoric acid.

Process for preparation of ultrapure thorium fluoride

Abstract: The specification discloses a process for the preparation of ultrapure thorium fluoride (ThF 4 ) having minimized water content and consequent maximized optical transmission of 10.6 micrometer radiation. First, thorium oxide is reacted with aqueous hydrofluoric acid to form a solid reaction product, which is then dried under controlled heating to form a hydrated thorium fluoride with a predetermined amount of hydration, namely ThF 4 .xH 2 O where x is equal to 0.39. The hydrated thorium fluoride is exposed to a reactive atmosphere of hydrofluoric acid vapor and a selected fluoride compound in the gas phase at elevated temperature for a predetermined period of time. The reactive atmosphere removes substantially all of the water and water-derived impurities from the hydrated thorium fluoride to produce ultrapure thorium fluoride which is highly transmissive to 10.6 micrometer radiation.

Production of potassium hexafluotitanates using dilute hydrofluoric acid

Abstract: A process is provided for recovering fluorine from dilute hydrofluoric acid solutions, such as waste scrubber solution obtained in the treatment of phosphates. The dilute solution is used to react with oxidic titanium material to solubilize the contained titanium and subsequently form, in the presence of potassium ions, crystals of K 2 TiF 6 which are commercially useful as a grain-refining agent in the manufacture of aluminum alloys.

Development of Hydrogen Ion Selective Electrode with Lithium Phosphate Glasses for the Use in Solutions Containing Hydrofluoric Acid

Abstract: In order to determine reproducible and stable potential response conditions of the hydrogen ion in hydrofluoric acid solutions, lithium phosphate glass membranes of various constituents were developed. The glass membranes contained various metal oxides: Ag2O, Li2O, P2O5, MgO, BeO, WO2, and Al2O3. The response characteristics of the glass electrode depend strongly on the glass compositions. For the examination of the selectivity coefficient and the electrode function of hydrogen ion activities, the glass composition of 10 Ag2O : 20 Li2O : 50 P2O5 : 10 MgO : 10 WO2 is the most suitable one. The potential response is linear over the hydrogen ion activities of (100.3–10−4) mol/dm3, and has a slope of 44.5 mV/decade change in the hydrogen ion activity at 20 °C. The dynamic response time was within a minute in the range 10−1 to 10−4 mol/dm3. The intereference of the various cations on the activity of about 0.1 mol/dm3 can be ignored during the determination of the hydrogen ion activities at pH below 3. Physical...

Perfluoro-cyclic-amine

Abstract: NEW MATERIAL:A compound of the formula (j, k are 0, 1; l, m, n are 0, 1, 2) EXAMPLE:Perfluoro-2-azatricyclo[5,2,2,0 , ]undecane USE:Blood substitute, oxygen-carrying transfusion solution PREPARATION:For example, a cyclic amine, as a starting material, such as 2- azatricyclo[5,2,2,0 , ]undecane is dissolved in anhydrous hydrofluoric acid and the solution is subjected to electrolysis in a bath of 4-12 degC under passing helium gas The reaction mixture separates into the upper layer of hydrofluoric acid and the bottom layer of fluorocarbon and the bottom layer is collected The collected reaction mixture is combined with sodium hydroxide and di-isobutylamine, then heated under reflux to remove the proton-containing compounds and the perfluoro product is obtained from the lowermost layer The product is combined with an emulsifier such as phospholipid and emulsified by means of a high pressure jetting type emulsifier to give a blood substitute

Preparation of C2 -C4 -olefins from methanol/dimethyl ether

Abstract: C 2 -C 4 -olefins are prepared by catalytic conversion of methanol and/or dimethyl ether in the presence of a zeolite catalyst at elevated temperatures, by a process in which the catalyst used is a pure borosilicate zeolite which has been tableted or extruded without a binder and treated with hydrofluoric acid and hydrochloric acid. The treatment of the catalyst with hydrofluoric acid is carried out using 0.001-1N HF, and that with hydrochloric acid is carried out using 3-25% strength acid. The time-on-stream of the catalyst is improved.

Determination of iron in semiconductor-grade silicon by furnace atomic-absorption spectrometry

Abstract: The determination of iron in semiconductor-grade silicon for device production by furnace atomic-absorption spectrometry is described for iron contents down to a level of 5 ng g–1 in slice and polycrystalline material. The silicon matrix is first removed by treatment with hydrofluoric acid - nitric acid. Reagent purification and the selection of the most suitable furnace materials have been studied. Surface iron contamination is assessed separately by a chemical etching technique.

Preparation of optical fiber having high strength

Abstract: PURPOSE:To prepare optical fiber having high strength, by etching the surface layer of a parent material for optical fiber with a solution of the hydrofluoric acid type, heating the parent material at high temperature, making the surface smooth, followed by spinning it. CONSTITUTION:A parent material for optical fiber is immersed in a solution of the hydrofluoric acid such as HF, fluorosulfuric acid, fluoronitric acid, etc., preferably ultrasonic washing is also carried out, the surface layer of the parent material is etched. The parent material after etching is heated at high temperature to make the surface smooth, and spun, to give optical fiber having high strength.

Method of cleaning semiconductor wafer

Abstract: PURPOSE:To provide an easy, quick and economical cleaning treatmen of a semiconductor wafer using a liquid mixture of hydrofluoric acid, sulfuric acid and hydrogen peroxide CONSTITUTION:The degree of etching on the various parts of the wafer is made uniform by determining the mixture ratio of hydrofluoric acid at an appropriate values lower than 15% Treating with this liquid mixture, the hydrogen peroxide oxidizes the wafer, then hydrofluoric acid etches it so that removal of fat, elimination heavy metal and etching can be performed at one time, economizing the process by reducing the use of expensive chemicals as well as reducing the processing time

Fluorinating method of organic compound

Abstract: PURPOSE:To substitute an organic compound having active chlorine or bromine with fluorine in high yield without side reactions even under conditions in which the conventional KF is unreactive, by using fine particulate anhydrous potassium fluoride obtained by the spray drying method in an aprotic organic solvent. CONSTITUTION:An organic compound having an active chlorine or bromine is substituted by fluorine in an aprotic organic solvent by using potassium fluoride. In the process, fine particulate anhydrous potassium fluoride having 1-50mu particle diameter obtained by the spray method is used. The anhydrous potassium fluoride is obtained by spraying a concentrated aqueous solution synthesized by neutralizing hydrofluoric acid with KOH, etc. in hot air at 300-600 deg.C in a spray dryer, drying the solution instantaneously, and recovering the dried particles from the hot air by a cyclone. The resultant KF has very slight hygroscopicity, and can be converted into a low-boiling solvent even in a system in which the reaction is carried out only in a high-boiling solvent. Thus, side reactions can be suppressed. The equipment can be also simplified.

Electroless plating method

Abstract: PURPOSE:To form a golden plated film with superior adhesive strength and corrosion resistance at a low cost by adding fluorine anion and carboxyl anion to an aqueous soln contg Sn iron and Cu ion and by carrying out electroless plating in the soln CONSTITUTION:Sn ion and Cu ion are incorporated in an aqueous soln used in plating in the form of metallic salts such as halides or sulfates Fluorine anoion is added to the soln in the form of an acid such as hydrofluoric acid or borofluoric acid, and carboxyl anion is added in the form of acetic acid, succinic acid or the like A compound such as tin silicofluoride may be used The concns of the ions are preferably adjusted to 0003-15mole/l Sn ion, 00004- 002mole/l Cu ion, 0003-24mole/l fluorine anion and 0005-07mole/l carboxyl anion When a product made of iron or other suitable material is plated by treatment with the aqueous soln having said composition, it can be plated only by immersion in the soln