Hydrofluoric acid physical 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. 

Lead Fluoride. Lead difluoiide, Pbp2, is a white oithorhombic salt to about 220°C where it is transformed into the cubic form some physical properties ate given in Table 1. Lead fluoride is soluble in nitric acid and insoluble in acetone and ammonia. It is formed by the action of hydrofluoric acid on lead hydroxide or carbonate, or by the reaction between potassium fluoride and lead nitrate. 

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. 

Exists in two adotropic modifications. Crystalline sihcon is made up of grayish-black lustrous needle-hke crystals or octahedral platelets cubic structure Amorphous sdicon is a brown powder. Other physical properties are density 2.33g/cm3 at 25°C melts at 1,414°C high purity liquid silicon has density 2.533 g/cm at its melting point vaporizes at 3,265°C vapor pressure 0.76 torr at 2,067°C Mohs hardness 6.5. Brinell hardness 250 poor conductor of electricity dielectiric constant 13 critical temperature 4°C calculated critical pressure 530 atm magnetic susceptibility (containing 0.085%Fe) 0.13x10 insoluble in water dissolves in hydrofluoric acid or a mixture of hydrofluoric and nitric acids soluble in molten alkalies. 

The physical properties of tantalum are similar to those of mild steel, with the exception that its melting point (2996°C) is much higher. It is ordinarily used in the pure form, and it is readily fabricated into many different shapes. The corrosion-resistance properties of tantalum resemble those of glass. The metal is attacked by hydrofluoric acid, by hot concentrated alkalies, and by materials containing free sulfur trioxide. It is resistant to all other acids and is often used for equipment involving contact with hydrochloric acid. 

Products of the degradation of molten fluoropolymers are highly corrosive, often containing hydrofluoric acid. The parts of the machine that come in contact with molten fluoropol5miers must be constructed from corrosion-resistant metals that are significantly more expensive than lower grades of steel. Corrosion of process surfaces can result in the contamination of the finished product and deterioration of its physical properties. 

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. 

PHYSICAL PROPERTIES soft, bulky, solid material (88% amorphous silica) composed of skeletons of small aquatic plants related to algae (diatoms) available as white to buff colored blocks, bricks, powder, etc. odorless solid insoluble in water insoluble in acids except hydrofluoric acid soluble in strong alkalies capable of absorbing 1.5-4 times its weight of wa-... 

PHYSICAL PROPERTIES white, cubic-system crystals formed from quartz or amorphous silica at temperatures above 1000°C (1832°F) odorless solid transparent and tasteless may be a component of many mineral dusts practically insoluble in water or acid, except hydrofluoric acid MP (1600°C, 2912°F) BP (2230°C, 4046 F) SG (2.66) VD (NA) VP (0 mmHg... 

PHYSICAL PROPERTIES white to reddish crystals odorless, tasteless solid component of many mineral dusts practically insoluble in water or acids, except hydrofluoric acid ... 

PHYSICAL PROPERTIES white or colorless platelets or orthorhombic crystals foimed from quartz at temperatures greater than 870°C (1598°F), with a 16.2% increase in volume odorless, tasteless solid insoluble in water and most acids but dissolves in hydrofluoric acids insoluble in organic solvents unlike quartz, it is soluble in boiling sodium carbonate solution MP (1710 C, 3110°F) BP (2230°C, 4046°F) DN (2.28-2.3 g/cm") SG (2.3) CP (44.4 J/K-mol crystal at 25°C) VD (NA) VP (0 mmFIg approximately at 20°C) MOFIS HARDNESS (7). 

PHYSICAL PROPERTIES black to steel-gray, lustrous crystals or black-brown amorphous powder dark-colored crystals are of the octahedral form, in which the atoms have a diamond arrangement practically insoluble in water, nitric acid, and hydrochloric acid soluble in hydrofluoric acid or in a mixture of nitric and hydrofluoric acids also soluble in molten alkali oxides MP (MIO C, 2570°F) BP (2355 C, 4271 F) DN (2.33 g/cm at 25 C) SG (2.33) CP (20.0 J/K-mol crystal at 25°C) VD (NA) VP (approximately 0 mmHg at 20°C, 1 mmHg at 1724 C) MOHS HARDNESS (7.0). 

PHYSICAL PROPERTIES The physical properties of metallic tantalum and tantalum pentoxide are provided for illustrative purposes, (metallic tantalum) steel-blue to gray solid or black powder very hard, malleable, ductile metal can readily be drawn in fine wires odorless insoluble in water insoluble in acids, except hydrofluoric and fuming sulfuric acids soluble in fused alkalies MP (2996"C, 5425"F) BP (5425 C, 9797T) DN/SG (16.65 (metal), 14.40 (powder)) CP (25.4 J/K-mol crystal at 25°C) VD (NA) VP (approximately 0 mmHg at 20 C) TS (130,000 psi) EC (8 x 10" over range 20 - 1500 C). (tantalum pentoxide) white, microcrystalline, infusible powder insoluble in water, acids, and alcohol soluble in hydrogen fluoride MP (1800 C, 3272 F) BP (NA) DN/SG (8.2) CP (135.1 J/K-mol crystal at 25"C) VD (NA) VP (approximately 0 mmHg at 20 C). 

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