The Properties and Reactions of Ammonium Fluorides

Rakov, E. G.; Mel'nichenko, E. I.

doi:10.1070/rc1984v053n09abeh003126

Cited by 40 publications

(34 citation statements)

References 98 publications

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“…by the formation of ammonium fluorometallates or oxofluorometallates. Silicon and its compounds form ammonium hexafluorosilicate, which decompose above 300°C [38]. The reaction of a mixture of SiO 2 and ΝΗ 4 ΗF 2 begins at a temperature of about 100°C and takes place exothermally to give (NH 4 ) 2 SiF 6 ×NH 4 F [38].…”

Section: Introductionmentioning

confidence: 99%

“…As potassium is a major element in most geological samples, only HF is needed for the stabilisation of boron in most geological sample solutions and attaining accurate analytical results [36]. As reviewed in the literature [38,39], different reaction products are created in the reaction of silicon or boron and its compounds (oxides, hydroxides, salts, etc.) if ammonium fluoride or ammonium hydrogen fluoride are the reagents.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of ammonium fluoride for quantitative microwave-assisted extraction of silicon and boron from different solid samples

Husáková

Urbanová

Šídová

et al. 2015

International Journal of Environmental Analytical Chemistry

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluation of ammonium fluoride for quantitative microwave-assisted extraction of silicon and boron from different solid samples

Husáková

Urbanová

Šídová

et al. 2015

International Journal of Environmental Analytical Chemistry

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“…Rakov and Mel'nichenko [5] reported that yttria, on reacting with NH 4 HF 2 , forms a compound NH 4 Y 2 F 7 ÁNH 4 F, which decomposes in two stages, at 260 and 380°C, to give NH 4 Y 2 F 7 and YF 3 . Patwe et al [6] reported that the fluorination of yttrium oxide using ammonium bifluoride at room temperature gave (NH 4 ) 3 YF 6 Á1.5H 2 O, which decomposed between 80 and 320°C to form YF 3 by losing NH 4 F and H 2 O. Kalinnikov et al [7] reported that the reaction between yttria and ammonium bifluoride yields the intermediates (NH 4 ) 3 Y 2 F 9 at 170°C and NH 4 Y 2 F 7 at 250°C, finally forming YF 3 at 350°C.…”

mentioning

confidence: 99%

“…Researchers [5][6][7] have suggested that the decomposition of the intermediates during the yttria fluorination reaction takes place through the thermal route. However, the kinetic parameters for the decomposition of the intermediates have not been reported in the open literature.…”

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Thermogravimetric studies and kinetics of decomposition of ammonium yttrium fluoride

Mukherjee

Mishra

Krishnamurthy

2011

Reac Kinet Mech Cat

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The kinetics of thermal decomposition of ammonium yttrium fluoride intermediates, (NH 4 ) 3 Y 2 F 9 and NH 4 Y 2 F 7 were studied by a non-isothermal thermogravimetric (TG) technique at different heating rates. Kinetic parameters were determined from the TG curves by using two model-free methods, i.e. Flynn-WallOzawa (FWO) and Kissinger-Akahira-Sunose (KAS). The activation energy (E) for the decomposition of (NH 4 ) 3 Y 2 F 9 was dependent on the fraction converted, a; its value was 152 kJ/mol (for a = 0.1-0.3) and 232 kJ/mol (for a = 0.4-0.8) from both models; and the pre-exponential factor (ln(A)) was 43 (for a = 0.1-0.3) and 59 (for a = 0.4-0.8). For the decomposition of NH 4 Y 2 F 7 , the activation energy (E) was independent of the fraction converted, a, and its value was 123 kJ/mol; the pre-exponential factor (ln(A)) was 31. The decomposition of (NH 4 ) 3 Y 2 F 9 proceeds by one-dimensional diffusion (for a = 0.1-0.3), followed by two-dimensional diffusion (for a = 0.4-0.8). The decomposition of NH 4 Y 2 F 7 occurs by random nucleation and growth.

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Rapid decomposition of geological samples by ammonium bifluoride (NH₄HF₂) for combined Hf‐Nd‐Sr isotope analyses

Újvári

Klötzli

Horschinegg

et al. 2021

Rapid Comm Mass Spectrometry

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Rationale Complete decomposition of silicate rock matrices is crucial in determining their isotopic compositions, but acid dissolution in a high‐pressure steel‐jacketed bomb, which has been the only powerful, effective technique thus far, is time‐consuming and expensive. Rock dissolution using ammonium bifluoride (ABF), as described here, is a viable alternative. Methods Geological reference materials (GRMs) were digested using ABF in closed Teflon beakers at temperatures of 220/230°C in a convection oven and subsequently treated with HNO3. Hf‐Sr‐Nd were separated and purified using ion‐exchange chemistry columns calibrated for 50–2 mg samples. The isotopic compositions of Sr‐Nd were measured by Thermal Ionization Mass Spectrometry, while that of Hf by Multi‐Collector Inductively Coupled Plasma Mass Spectrometry, both with normal 1011 Ω and gain calibrated 1013 Ω amplifiers. Results Total procedural blanks of our protocol are 0.5 ng for Sr, 0.2 ng for Nd and <25 pg for Hf. Test runs with GRMs, ranging in composition from basic to felsic and dissolved in ABF, yield accurate 87Sr/86Sr, 143Nd/144Nd and 176Hf/177Hf isotope ratios as compared with those obtained with the bomb dissolution technique. Reproducibilities were comparable, on the order of 10–20 ppm. Our technique allows combined Hf‐Sr‐Nd isotope analyses of low‐mass (50–2 mg) samples. Conclusions The ABF digestion is an alternative technique to high‐pressure bomb dissolution in matrix decomposition for accurate and reproducible Hf‐Nd‐Sr isotope analyses of geological samples within a reasonable time (3–4 days), with high sample throughput and low costs in geochemistry and environmental sciences.

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The Properties and Reactions of Ammonium Fluorides

Cited by 40 publications

References 98 publications

Evaluation of ammonium fluoride for quantitative microwave-assisted extraction of silicon and boron from different solid samples

Evaluation of ammonium fluoride for quantitative microwave-assisted extraction of silicon and boron from different solid samples

Thermogravimetric studies and kinetics of decomposition of ammonium yttrium fluoride

Rapid decomposition of geological samples by ammonium bifluoride (NH₄HF₂) for combined Hf‐Nd‐Sr isotope analyses

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The Properties and Reactions of Ammonium Fluorides

Cited by 40 publications

References 98 publications

Evaluation of ammonium fluoride for quantitative microwave-assisted extraction of silicon and boron from different solid samples

Evaluation of ammonium fluoride for quantitative microwave-assisted extraction of silicon and boron from different solid samples

Thermogravimetric studies and kinetics of decomposition of ammonium yttrium fluoride

Rapid decomposition of geological samples by ammonium bifluoride (NH4HF2) for combined Hf‐Nd‐Sr isotope analyses

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Rapid decomposition of geological samples by ammonium bifluoride (NH₄HF₂) for combined Hf‐Nd‐Sr isotope analyses