Hydrogen fluoride, ammonium

Zirconium is readily attacked by acidic solutions containing fluorides. As Httle as 3 ppm flouride ion in 50% boiling sulfuric acid corrodes zirconium at 1.25 mm/yr. Solutions of ammonium hydrogen fluoride or potassium hydrogen fluoride have been used for pickling and electropolishing zirconium. Commercial pickling is conducted with nitric—hydrofluoric acid mixtures (see Metal surface treatments). 

Chemical Designatioiis - Synonyms Acid Ammonium Fluoride, Ammonium Acid Fluoride, Ammonium Hydrogen Fluoride Chemical Formula NH NF. ... 

The Crystal Structure of Ammonium Hydrogen Fluoride, NH4HF2... 

Ammonium hydrogen fluoride (NH4HF2) is useful for converting pure oxides or hydroxides to the corresponding fluorides. The reaction occurs through the formation of a double fluoride. For example, with vanadium sesquioxide the following reactions occur ... 

Ammonium fluoride, or Ammonium hydrogen fluoride Gardner, D. M. et al., Inorg. Chem., 1963, 2, 413... 

The reaction gases (containing chlorodifluoramine) must be handled at below —5°C to avoid explosion. Ammonium hydrogen fluoride behaves similarly. 

Schwenzfeier-Pomelee A process for purifying beryllium and producing glassy beryllium fluoride. Beryllium hydroxide is dissolved in aqueous ammonium hydrogen fluoride various metal impurities are removed by successive precipitations, and ammonium fluoroberyllate is crystallized under vacuum. When this is heated, ammonium fluoride vaporizes and molten beryllium fluoride remains. 

Formula NH4HF2 MW 57.04 Synonym ammonium hydrogen fluoride... 

The ore thortveitite is crushed and powdered. It is mixed with a large excess of ammonium hydrogen fluoride and heated at about 400°C for several hours in a platinum container under a stream of dry air. Silica is converted to volatile silicon tetrafluoride and swept out with dry air. Scandium oxide is converted to scandium trifluoride, SCF3 ... 

Yttrium oxalate is then ignited to its oxide, Y2O3. The oxide is heated at 750°C in a stream of anhydrous hydrogen fluoride to yield yttrium fluoride, YF3. Alternatively, the oxide is mixed with ammonium hydrogen fluoride NH4HF2 and heated at 400°C in a stream of dry air or helium. Yttrium metal may be produced from its fluoride either by metallothermic reduction or electrolysis. The more common metallothermic reduction involves reducing the fluoride with redistilled calcium in 10% excess over the stoichiometric amounts at elevated temperatures ... 

Synonym Ammonia Water Amfbnioformaldehyde Ammonium Acetate Ammonium Acid Fluoride Ammonium Amidosulfonate Ammonium Amidosulphate Ammonium Benzoate Ammonium Bicarbonate Ammonium Bichromate Ammonium Bifluoride Ammonium Carbonate Ammonium Chloride Ammonium Citrate Ammonium Citrate, Dibasic Ammonium Decaborate Octahydrate Ammonium Dichromate Ammonium Disulfate-Nickelate (II) Ammonium Ferric Citrate Ammonium Ferric Oxalate Trihydrate Ammonium Ferrous Sulfate Ammonium Fluoride Ammonium Fluosilicate Ammonium Formate Ammonium Gluconate Ammonium Hydrogen Carbonate Ammonium Hydrogen Fluoride Ammonium Hydrogen Sulfide Solution Ammonium Hydroxide Ammonium Hypo Ammonium Hyposulfite Ammonium Iodide Ammonium Iron Sulfate Ammonium Lactate Ammonium Lactate Syrup Ammonium Lauryl Sulfate Ammonium Molybdate Ammonium Muriate Ammonium Nickel Sulfate Ammonium Nitrate Ammonium Nitrate-Urea Solution Ammonium Oleate... 

The procedures discussed for aromatics can readily be adopted for the efficient preparation of fluoro-substituted heteroaromatics.141,143,149 150 Fluorodediazoniations of 2-ainino-, 3-amino-, 4-amino- and 2.6-diamino-substituted pyridines and some of the chloro or bromo derivatives have been carried out in liquid hydrogen fluoride with anhydrous sodium nitrite. About 1.2 equivalents of nitrite are used per amino group, and ammonium hydrogen fluoride has also been added. The corresponding fluoropyridines or their hydrochlorides have been obtained in 49-89% yield.150 For example, the reported synthesis150 is suitable for the preparation of larger quantities of 4-fluoropyridine hydrochloride (54% yield mp 100 C) examples are given by the formation of 5-7.150... 

Ammonium salts such as those with the formula NH4F - nHF, among which ammonium hydrogen fluoride (n = 1) is preferred.25-31-49 65 In addition to its action on the vapor pressure, NH4+ HF2, used in such an amount that NH4+/(F + HF) = 0.03 to 0.15 (mol/mol), improves the yield of the fluorinated product and makes the final decantation and recovery of hydrogen fluoride easier. Typical improved yields are given below. 

However, the method is no longer satisfactorily applicable to synthesis of higher polysilane derivatives because extensive cleavage of the silicon-silicon bond occurs and a mixture of isomeric halopolysilane derivatives that are inseparable by distillation is formed. For example, the reaction of decamethyltetrasilane with sulfuric acid and treatment with ammonium hydrogen fluoride leads to the formation of several fluoro derivatives of... 

Thus, the action of sulfuric acid on 1,1-diphenyltetramethyldisilane below 10° C followed by treatment with ammonium chloride gives 1,1-dichlorotetramethyldisilane in 60% yield (116). Similarly, dephenylation by sulfuric acid of 1,2-diphenyl-1,2-dimethyl-1,2-disilacycloheptane gives, after treatment with ammonium hydrogen fluoride, 1,2-difluoro-1,2-dimethyl-1,2-disilacycloheptane in 81% yield (112, 124), whereas this product can not advantageously be obtained from the 1,1,2,2-tetramethyl compound (see Section III, C,4). 

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