Hydrofluoric acid chemical properties

Properties. Lithium fluoride [7789-24-4] LiF, is a white nonhygroscopic crystaUine material that does not form a hydrate. The properties of lithium fluoride are similar to the aLkaline-earth fluorides. The solubility in water is quite low and chemical reactivity is low, similar to that of calcium fluoride and magnesium fluoride. Several chemical and physical properties of lithium fluoride are listed in Table 1. At high temperatures, lithium fluoride hydroly2es to hydrogen fluoride when heated in the presence of moisture. A bifluoride [12159-92-17, LiF HF, which forms on reaction of LiF with hydrofluoric acid, is unstable to loss of HF in the solid form. 

Chemical Properties. Sulfur tetrafluoride reacts rapidly with water to give hydrofluoric acid and thionyl fluoride [7783 2-8] ... 

Alkylate. Alkylation means the chemical combination of isobutane with any one or a combination of propylene, butylenes, and amylenes to produce a mixture of highly branched paraffins that have high antiknock properties with good stabiUty. These reactions are cataly2ed by strong acids such as sulfuric or hydrofluoric acid and have been studied extensively (98—103). In the United States mostly butylenes and propylene are used as the olefins. 

It is common practice to refer to the molecular species HX and also the pure (anhydrous) compounds as hydrogen halides, and to call their aqueous solutions hydrohalic acids. Both the anhydrous compounds and their aqueous solutions will be considered in this section. HCl and hydrochloric acid are major industrial chemicals and there is also a substantial production of HF and hydrofluoric acid. HBr and hydrobromic acid are made on a much smaller scale and there seems to be little industrial demand for HI and hydriodic acid. It will be convenient to discuss first the preparation and industrial uses of the compounds and then to consider their molecular and bulk physical properties. The chemical reactivity of the anhydrous compounds and their acidic aqueous solutions will then be reviewed, and the section concludes with a discussion of the anhydrous compounds as nonaqueous solvents. 

Nitryl fluoride may be identified from its physical and chemical properties. Its hydrolysis products, nitric and hydrofluoric acids, may be measured by selective ion electrodes or by ion chromatography. The gas, diluted in hehum or hydrogen (in cold), may be identified by GC/MS. 

Vitreous Silica Vitreous sdica is a glass form of sdica composed of Si02. It may be transparent, translucent, or opaque. It has a number of abnormal and anomalous properties in thermal expansion, viscosity, bulk density, compressibility, and elasticity. These properties depend on thermal history and preparation method. Vitreous sdica exhibits high resistance to chemical attack. At ambient temperature, it is not attacked by any chemical except hydrofluoric acid. 

Tungsten Trisilicide, WS%, was isolated by Frilley from a mi.xed iron tungsten silicide containing 9 per cent, iron, 51-6 per cent, tungsten, and 38-4 per cent, silicon by successive treatment with concentrated hydrofluoric acid, hot concentrated sodium liydroxide, and dilute hydrofluoric acid. The crystals obtained were white and lustrous, and exhibited similar chemical properties to those of the disilicide. 

The properties that make granite an attractive chemically resistant masonry are its naturally low permeability, thermal expansion (in generally the same range as that of "acid-brick"), high strength and the insolubility of its component minerals in dilute HCI and H2SO4. Hydrofluoric acid is the only acid in which quartz, feldspar and mica, the major constituents of most industrial granites, are easily soluble. Contact with HF must therefore be avoided. 

Properties Color varies from gray (transition-metal) to black (alkaline-earth) to blue (rare-earth). Highly refractory, with mp from 2000 to 3000C Mohs hardness from 8 to 10 thermally and electrically conductive. High chemical stability. Does not react with hydrochloric or hydrofluoric acids but is attacked by hot alkali hydroxides. 

Properties Silvery-white solid. Mp 1539C, bp 2727C, d 2.99. Does not tarnish in air, reacts rapidly with acids, strongly electropositive. Not attacked by 1 1 mixture of nitric and 48% hydrofluoric acids. It is chemically similar to the rare earths. 

Discussion Hydrofluoric acid is too corrosive and poison- ous a substance to be prepared by an elementary class in sufficient quantities to observe its physical properties. Enough can be made, however, to show its action on glass, which is one of its most important chemical reactions. 

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