Potassium fluoride flux

Because barium titanate has interesting properties, many methods have been used to grow single crystals of this compound. One of the most popular techniques, using a potassium fluoride flux, was first employed by Remeika.1... 

Aluminum fluoride Lithium fluoride flux, hard solder Potassium fluoride flux, magnesium prod. 

Potassium fluoride is a fluorinating agent in organic synthesis. Other applications are in making insecticide formulations, as an additive to flux for making hard solder, and to control fermentation. 

Fusion with anhydrous potassium fluoride in a platinum dish is undoubtedly the simplest, most effective and reliable method available for the complete dissolution of a wide variety of siliceous materials. The potassium fluoride cake can then be transposed in the same container to a pyrosulfate fusion with rapid and complete volatilisation of both hydrogen fluoride and silicon tetrafluoride [54]. Except for a small quantity of barium sulfate, the pyrosulfate cake will dissolve completely in dilute hydrochloric acid. The resulting pyrosulfate fusion is one of the simplest and most effective methods available for rapid, complete and dependable dissolution of nonsiliceous materials, particularly high-fired oxides. This fusion has the distinct advantage that the flux can be obtained by simply adding easily purified alkali metal sulfates to sulfuric acid, and the fusion can be carried out in either borosilicate flasks or platinum vessels with very little contamination from either reagents or containers. 

Joining silver pieces with silver solder requires temperatures of 316-760°C. At these temperatures, impurities in the silver solder, such as antimony and cadmium, are released. The flux may contain fluoride compounds, such as potassium fluoride and boron trifluoride, or other boron compounds. 

USE In the prepn of pure potassium fluoride as an electrolyte in the manuf of fluorine frosting glass treating coal to prevent slag formation flux [or diver solders catalyst in the alkylation of benzene with olefins. Caution Corrosive and irritating to skin, mucous membranes. 

Potassium fluoride is used as a fluoridating agent—a substance that provides fluorine atoms to other compounds—in the preparation of organic chemicals. It also finds some use in the field of metallurgy, where it is used as a flux, to finish metals, to make coatings for metals, and in tin... 

Preparation from Beryl.—Since beryl is not directly attacked by any acid, except, perhaps, by hydrofluoric when ground to a dust, it must first be fused with some flux or be heated in the electric furnace to a temperature (Lebeau, 1895 5) which volatilizes some of the silica and leaves a residue easily attacked by hydrofluoric acid. For those having the facilities, this latter method presents many advantages. Among the fluxes whicl can be successfully used are sodium and potassium carbonates, calcium fluoride, potassium fluoride, calcium oxide, and sodium and potassium hydroxide. The fluorides possess the advantage in subsequent treatment, in the comparative ease of removal of the large... 

The mineral fluorspar had been used as a flux since the middle ages (the name comes from the Latin meaning yZow), and in the Traite Lavoisier had included the fluoric radical as a simple substance (element) as yet unknown. Scheele obtained hydrofluoric acid in 1771. In 1813 Ampere pointed out the many similarities between the fluoric and muriatic (chlorine) compounds. He suggested the unknown element be called fluorine, and in the same year Humphry Davy tried to prepare it by the electrolysis of hydrofluoric acid. The corrosive nature of the acid presented insuperable problems, and it was to be another 73 years before the isolation of the element was achieved. During that time the toxic nature of fluorine compounds was to be responsible for the deaths of at least two chemists and was to ruin the health of many more. Success was finally achieved by Henri Moissan (1852-1907), who electrolysed potassium fluoride dissolved in anhydrous hydrofluoric acid using platinum apparatus. 

To move now to the aluminum industry, a similar question was being asked, although the context of the question was different. Aluminum is produced by the electrolytic reduction of aluminum oxide/fluoride fluxes at temperatures of about 1(X)0°C, less than the maximum temperatures of a blast furnace (about 1300 °C). The reductant is the carbon anode which is a block of calcined carbon weighing about 1 tonne which has to be inserted into the electrolytic cell. From time to time, these anodes would fail and fall into the molten electrolyte from which they would have to be extracted (a procedure not looked upon with favor within the industry). A major cause of this problem was eventually associated with the presence of sodium (less so with potassium) within the calcined coke. The question to be solved at that time was how does sodium cause degradation and weakening of the carbon anode. 

HISTORY. Fluorine was first isolated in 1886 by Henri Moissan, a Frenchman, who obtained it by the electrolysis of anhydrous hydrogen fluoride containing dissolved potassium fluoride. The name fluorine is derived from the Latin fluo, meaning to flow, because until 1500 A. D. it was used as a flux in metallurgy. 

Welding flux comprises equimolar mixtures of lithium chloride and potassium chloride with an addition of lithium fluoride, sodium fluoride, potassium fluoride or... 

Crystals of barium titanate can be grown with a mixture of 30% barium titanate by weight and anhydrous potassium fluoride. In a specific procedure, 28 g of barium titanate [or 23.6 g (0.1 mol) of barium carbonate and 9.6 g (0.12 mol) of titanium(IV) oxide] is placed in a 50-mL platinum crucible and covered with 66 g of anhydrous potassium fluoride. The cover is placed on the crucible, and the crucible and contents are heated to 1160 °. When barium carbonate and titanium(IV) oxide are used with potassium fluoride, the contents of the crucible are first slowly melted before the cover is placed on tightly and the mixture heated to 1160°. After being held for 12 h at 1160°, the crucible is cooled 25 °/h at 900 °, and the flux is poured off. The crystals then are annealed by slowly cooling them to room temperature, and they are removed by soaking the crucible contents in hot water. 

Naturally, the flux employed will depend upon the nature of the insoluble substance. Thus acidic materials are attacked by basic fluxes (carbonates, hydroxides, metaborates), whilst basic materials are attacked by acidic fluxes (pyroborates, pyrosulphates, and acid fluorides). In some instances an oxidising medium is useful, in which case sodium peroxide or sodium carbonate mixed with sodium peroxide or potassium nitrate may be used. The vessel in which fusion is effected must be carefully chosen platinum crucibles are employed for... 

Potassium Bifluoride (Potassium Acid Fluoride), KHFa, mw 78.11 colorless, poisonous corrosive crysrs mp — decomp sol in w dil ale insol in abs ale. Can be prepd by crystallizing from an aq soln of KF in HF (Ref 1). Used for etching glass production of fluorine and of flux in metallurgy Rsfs ]) Gmel in-Kraut 3ysf Nunibcr 22(1937)... 

A rapid, alternative method of crystal separation is the addition of solid potassium chloride (an amount necessary to fill the crucible) directly into the untreated, fused mass (obtained after cooling to room temperature), followed by heating the new mixture to its fusion point by means of a Meker burner in a fume hood and maintaining this temperature for 1 or 2 hours. The molten potassium chloride will rapidly dissolve the magnesium fluoride and decompose the tungstate. The crucible is allowed to cool, and the fused mass is treated as described in the previous section. However, dissolving of the flux will now be much more rapid. 

Boric acid Copper oxide (ic) Lithium chloride Lithium fluoride Potassium tetraborate Tributyl borate Zirconium potassium hexafluoride welding flux, gaseous Trimethyl borate welding fluxes, special Zirconium welding gas Oxygen... 

The weakly nitric-acid solution obtained as a result of concentration of the water sample is extracted with ethyl acetate following the addition of aluminium nitrate. The organic phase containing the uranium is separated off, evaporated in a platinum crucible, and the uranium is melted at 630 °C after adding sodium fluoride/potassium carbonate/sodium carbonate as a fluxing agent. The yellow-green fluorescence of the melt which appears when irradiated with an ultraviolet lamp is compared with that of standard samples prepared under equivalent conditions. 

Fluorine had been suspected as an element present in the mineral fluorite (CaF2) and had been officially named in 1812 by A. M. Ampere and H. Davy (Latin fluere, to flow, from the use of fluorite as a flux). Its isolation, however, remained one of the chief unsolved problems of inorganic chemistry for more than 70 years because of the great reactivity of this element. In 1886, the French chemist H. Moissan successfully prepared elemental fluorine by the electrolysis of a cooled solution of dry potassium hydrogen fluoride (KHF2) in anhydrous hydrofluoric... 

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