| Identification | More | [Name]
HAFNIUM | [CAS]
7440-58-6 | [Synonyms]
GFE 1
RAMBACH
HAFNIUM
celtium
HF004500
HF000210
HF000110
HF000150
HF000130
HF000200
HF007900
HF000205
HF000230
HF000090
HF000220
HF005130
HF000190
HF000214
HF005110
HF005120
HF000140
HF000120
HF000170
HF000160
HF000180
HF000240
HF007910
HF007902
HF000100
HF005105
Hafnium rod
hafnium atom
HAFNIUM FOIL
hafniumpowder
Hafnium plate
HAFNIUM METAL
HafniumZrwire
HAFNIUM SPONGE
Hafnium element
HafniumpowderZr
Hf Target 99.9%
Hafnium wire（Hf）
HAFNIUM STANDARD
hafniumpowder,dry
Hafnium foil (99.5%
Hafnium wire (99.7%
Hafnium foil50x80mm
Hafnium foil50x50mm
CHROMOCULT COLIFORM
HAFNIUM ICP STANDARD
Hafnium, crystal Bar
Hafnium foil80x250mm
Hafnium wire (99.97%
HafniumpowderNZrmesh
Hafnium foil100x100mm
HAFNIUM SPONGE, 99.8%
hafniummetal,dry(dot)
hafniummetal,wet(dot)
HafniumwireNZrmmdiagcm
hafnium powder, wetted
Hafnium metal powder,dry
Hafnium, powder, -20 Mesh
Hafniumfoil(99.5%,Zr-2.9%)
Hafnium, Crystal Bar 99.7%
HAFNIUM ISO 9001：2015 REACH
Hafnium, Powder 20 Mesh 99.6%
HafniumBars,Crystalline,99.9%
HAFNIUM WIRE (99.7%, ZR-3.1%)
HAFNIUM WIRE (99.97%, ZR-3.1%)
HafniumfoilNZrmmthickxmmwidegx
HAFNIUM, AAS STANDARD SOLUTION
HAFNIUM SINGLE ELEMENT STANDARD
Hafnium, sponge, -0.75+ 20 Mesh
HAFNIUM POWDER (99.6%, ZR-3.1%)
HAFNIUM POWDER (99.6%, ZR-2.2%)
Hafnium crystal bar chips (99.7%
HAFNIUM, SPONGE, +20 MESH, 99.5%
HAFNIUM PLASMA EMISSION STANDARD
HafniuM slug,2MM dia×3MM length.
HAFNIUM, PLASMA STANDARD SOLUTION
HAFNIUM FOIL 0.5MM THICK 99.5%
HAFNIUM, POWDER, -325 MESH, 99.5%
HAFNIUM, FOIL, 0.25MM THICK, 99.5%
HAFNIUM, WIRE, 1.0MM DIAM., 99.9+%
HAFNIUM, FOIL, 0.02MM THICK, 99.5%
HAFNIUM ATOMIC ABSORPTION STANDARD
POTASSIUM ACETATE BIOLOGICAL GRADE
Hafnium Rod/Φ3x100mm/99.9% (Zr<2%)
Hafnium Rod/Φ6x100mm/99.9% (Zr<2%)
Hafnium, 0.025mm (0.001 in.) thick
Hafnium rod, 6.35mm (0.25 in.) dia.
Hafnium wire, 1.0mm (0.04 in.) dia.
Hafnium wire, 2.0mm (0.08 in.) dia.
HAFNIUM, PLATE, 6.5MM X 25MM X 25MM
Hafnium wire, 0.5mm (0.02 in.) dia.
Hafniumcrystalbarchips(99.7%,Zr-~3%)
Hafnium, Sponge 0.75''+20 Mesh 99.6%
Hafnium wire, 0.25mm (0.01 in.) dia.
Hafnium foil, 0.75mm (0.03 in.) thick
HAFNIUM, TURNINGS, CRYSTAL BAR, 99.7%
Hafnium wire, 1.57mm (0.0618 in.) dia.
Hafnium Foil/0.10x50x50 mm/99.9% (Zr<2%)
Hafnium Target/Φ50.8x6.3mm/99.9% (Zr<2%)
Hafnium Target/Φ50.8x3.2mm/99.9% (Zr<2%)
Hafnium Foil/0.25x50x50 mm/99.9% (Zr<2%)
Hafnium Foil/0.50x50x50 mm/99.9% (Zr<2%)
Hafnium Foil/1.00x50x50 mm/99.9% (Zr<2%)
HAFNIUM ICP STANDARD TRACEABLE TO SRM FR
HAFNIUM FOIL (99.5%, ZR-2.9%) 1.0MM THICK
HAFNIUM CRYSTAL BAR CHIPS (99.7%, ZR-3.4%)
Hafnium, plate, 6.5mm x 25mm x 25mm, 99.5%
HAFNIUM FOIL (99.5%, ZR-2.9%) 0.254MM THICK
hafniumpowder,wettedwithnotlessthan25%water
HAFNIUM ATOMIC ABSORPTION STANDARD SOLUTION
Hafnium, AAS standard solution, Hf 1000μg/mL
Hafnium pieces, 3 to 12mm (0.12 to 0.47 in.)
Hafnium arc-cast pellet, 12mm (0.47 in.) dia.
HAFNIUM PLASMA EMISSION SPECTROSCOPY STANDARD
Hafnium plasma standard solution, Hf 1000μg/mL
Hafnium standard solution, 1 mg/ml Hf in 5% HF
Hafnium plasma standard solution, Hf 10000μg/mL
Hafnium foil, 0.25mm (0.01 in.) thick, Annealed
HAFNIUM FOIL (99.5%, ZR-2.9%) 0.025MM THICK X 100 MM WIDE
Hafnium, AAS standard solution, Specpure(R), Hf 1000μg/ml
HAFNIUM FOIL, 1.0MM (0.04IN) THICK, ANNEALED, 99.5% (METALS
HAFNIUM POWDER, -60+325 MESH, 99.6% (METALS BASIS EXCLUDING
HAFNIUM WIRE, 0.25MM (0.01IN) DIA, 99.97% (METALS BASIS EXCL
HAFNIUM CRYSTAL BAR, 99.7% (METALS BASIS EXCLUDING ZR), ZR N
HAFNIUM FOIL, 0.75MM (0.03IN) THICK, 99.5% (METALS BASIS EXC
HAFNIUM WIRE, 1.57MM (0.0618IN) DIA, 99.7% (METALS BASIS EXC
HAFNIUM WIRE, 2.0MM (0.08IN) DIA, 99.7% (METALS BASIS EXCLUD
HAFNIUM PIECES, 3-12MM (0.12-0.47IN), 99.9% (METALS BASIS EX
HAFNIUM FOIL, 0.025MM (0.001IN) THICK, 99.5% (METALS BASIS E
HAFNIUM WIRE, 0.5MM (0.02IN) DIA, 99.95% (METALS BASIS EXCLU
Hafnium foil, 1.0mm (0.04 in.) thick, Annealed, Temper: soft
HAFNIUM WIRE, 1.0MM (0.04IN) DIA, 99.95% (METALS BASIS EXCLU
Hafnium, plasma standard solution, Specpure(R), Hf 1000μg/ml
Hafnium pieces, 3-12mm, 99.9% trace metals basis excluding Zr
Hafnium, plasma standard solution, Specpure(R), Hf 10,000μg/ml
Hafnium powder, -325 mesh, 99.5% trace metals basis excluding Zr
Hafnium crystal bar milled chips, 99.5% trace metals basis excluding Zr
Hafnium crystal bar milled chips, 99.7% (metals basis excluding Zr), Zr nominal 3%
Hafnium wire, 1.0mm (0.04in) dia, 99.95% (metals basis excluding Zr), Zr nominal 3%
Hafnium wire, 1.57mm (0.0618in) dia, 99.7% (metals basis excluding Zr), Zr nominal 3%
Hafnium sponge, 0.8-20mm (0.03-0.79in), 99.6% (metals basis excluding Zr), Zr nominal 3%
Hafnium arc-cast pellet, 12mm (0.47in) dia, 99.8% (metals basis excluding Zr), Zr nominal 4.5%
Hafnium foil, 0.25mm (0.01in) thick, annealed, 99.5% (metals basis excluding Zr), Zr nominal 3%
Hafnium powder, -325 mesh, 99.5% trace metals basis (purity excludes ~2% zirconium), contains 1:10 pentanol to water solution as stabilizer | [EINECS(EC#)]
231-166-4 | [Molecular Formula]
Hf | [MDL Number]
MFCD00011032 | [Molecular Weight]
178.49 | [MOL File]
7440-58-6.mol |
| Chemical Properties | Back Directory | [Appearance]
Hafnium is a refractory metal which occurs in
nature in zirconium minerals. | [Melting point ]
2227 °C(lit.)
| [Boiling point ]
4602 °C(lit.)
| [density ]
13,31 g/cm3 | [storage temp. ]
Store at +15°C to +25°C. | [solubility ]
soluble in HF | [form ]
wire
| [color ]
Silver-gray | [Specific Gravity]
13.31 | [Stability:]
Stable. Incompatible with oxygen, sulfur, strong oxidizing agents, halogens, phosphorus, strong acids. Highly flammable. | [Resistivity]
29.6 μΩ-cm, 0°C | [Water Solubility ]
soluble HF; slowly reacts with conc H2SO4, aqua regia [KIR80] | [Merck ]
13,4603 | [Exposure limits]
ACGIH: Ceiling 2 ppm
OSHA: Ceiling 5 ppm(7 mg/m3)
NIOSH: IDLH 50 ppm; Ceiling 5 ppm(7 mg/m3) | [InChIKey]
VBJZVLUMGGDVMO-UHFFFAOYSA-N | [History]
Hafnium was thought to be present in various minerals and concentrations many years prior to its discovery, in 1923, credited to D. Coster and G. von Hevesey. On the basis of the Bohr theory, the new element was expected to be associated with zirconium. It was finally identified in zircon from Norway, by means of X-ray spectroscopic analysis. Hafnium was named in honor of the city in which the discovery was made. Most zirconium minerals contain 1 to 5% hafnium. It was originally separated from zirconium by repeated recrystallization of the double ammonium or potassium fluorides by von Hevesey and Jantzen. Metallic hafnium was first prepared by van Arkel and deBoer by passing the vapor of the tetraiodide over a heated tungsten filament. Almost all hafnium metal now produced is made by reducing the tetrachloride with magnesium or with sodium (Kroll Process). Hafnium is a ductile metal with a brilliant silver luster. Its properties are considerably influenced by the impurities of zirconium present. Of all the elements, zirconium and hafnium are two of the most difficult to separate. Their chemistry is almost identical; however, the density of zirconium is about half that of hafnium. Very pure hafnium has been produced, with zirconium being the major impurity. Natural hafnium contains six isotopes, one of which is slightly radioactive. Hafnium has a total of 41 recognized isotopes and isomers. Because hafnium has a good absorption cross section for thermal neutrons (almost 600 times that of zirconium), has excellent mechanical properties, and is extremely corrosion resistant, it is used for reactor control rods. Such rods are used in nuclear submarines. Hafnium has been successfully alloyed with iron, titanium, niobium, tantalum, and other metals. Hafnium carbide is the most refractory binary composition known, and the nitride is the most refractory of all known metal nitrides (m.p. 3310°C). Hafnium is used in gas-filled and incandescent lamps, and is an efficient “getter” for scavenging oxygen and nitrogen. Finely divided hafnium is pyrophoric and can ignite spontaneously in air. Care should be taken when machining the metal or when handling hot sponge hafnium. At 700°C hafnium rapidly absorbs hydrogen to form the composition HfH1.86. Hafnium is resistant to concentrated alkalis, but at elevated temperatures reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Halogens react directly to form tetrahalides. The price of the metal is about $2/g. The yearly demand for hafnium in the U.S. is now in excess of 50,000 kg. | [CAS DataBase Reference]
7440-58-6(CAS DataBase Reference) | [EPA Substance Registry System]
Hafnium (7440-58-6) |
| Hazard Information | Back Directory | [Chemical Properties]
Hafnium is a refractory metal which occurs in
nature in zirconium minerals. | [Chemical Properties]
solid | [General Description]
HAFNIUM POWDER, DRY(7440-58-6), is a grayish metallic colored powder. Dust from dry powder may be ignited by static electricity. The dry powder reacts with moisture to produce hydrogen, a flammable gas. The heat from this reaction may be sufficient to ignite the hydrogen. HAFNIUM POWDER, DRY(7440-58-6) does not appreciably react with large quantities of water. | [Reactivity Profile]
Metals, such as HAFNIUM METAL(reactivity similar to zirconium), are reducing agents and tend to react with oxidizing agents. Their reactivity is strongly influenced by their state of subdivision: in bulk they often resist chemical combination; in powdered form they may react very rapidly. Thus, as a bulk metal HAFNIUM POWDER, DRY is somewhat unreactive, but finely divided material may be pyrophoric. The metal reacts exothermically with compounds having active hydrogen atoms (such as acids and water) to form flammable hydrogen gas and caustic products. The reactions are less vigorous than the similar reactions of alkali metals, but the released heat can still ignite the released hydrogen. Materials in this group may react with azo/diazo compounds to form explosive products. These metals and the products of their corrosion by air and water can catalyze polymerization reactions in several classes of organic compounds; these polymerizations sometimes proceed rapidly or even explosively. Some metals in this group form explosive products with halogenated hydrocarbons. | [Air & Water Reactions]
Highly flammable. The dry powder reacts with moisture to produce hydrogen, a flammable gas. The heat from this reaction may be sufficient to ignite the hydrogen. HAFNIUM POWDER, DRY does not appreciably react with large quantities of water. | [Health Hazard]
Fire will produce irritating, corrosive and/or toxic gases. Inhalation of decomposition products may cause severe injury or death. Contact with substance may cause severe burns to skin and eyes. Runoff from fire control may cause pollution. | [Potential Exposure]
Hafnium metal has been used as a
control rod material in nuclear reactors. Thus, those
engaged in fabrication and machining of such rods may be
exposed. | [Fire Hazard]
Flammable/combustible material. May ignite on contact with moist air or moisture. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. Some may decompose explosively when heated or involved in a fire. May re-ignite after fire is extinguished. Runoff may create fire or explosion hazard. Containers may explode when heated. | [First aid]
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions, includ ing resuscitation mask) if breathing has stopped and CPR if
heart action has stopped. Transfer promptly to a medical
facility. When this chemical has been swallowed, get medi cal attention. Give large quantities of water and induce
vomiting. Do not make an unconscious person vomit. | [Shipping]
UN1326 Hafnium powder, wetted with not
<,25% water (a visible excess of water must be present)
(1) mechanically produced, particle size<53 μm; (2)
chemically produced, particle size<840 μm, Hazard Class:
4.1; Labels: 4.1-Flammable solid. UN2545 Hafnium pow der, dry, Hazard Class: 4.1; Labels: 4.1-Flammable solid.
UN1346 Hafnium powder, wetted with not less than 25%
water (a visible excess of water must be present)
(1) mechanically produced, particle size less than 53 μm;
(2) chemically produced, particle size less than 840 μm,
Hazard Class: 4.1; Labels: 4.1-Flammable solid. | [Incompatibilities]
Fine powder or dust may form explosive
mixture in air. The powder is highly flammable and a strong
reducing agent. The powder or dust reacts with moisture
forming flammable hydrogen gas; may spontaneously ignite
on contact with moist air; and at higher temperatures, with
nitrogen, phosphorous, oxygen, halogens, and sulfur; contact
with hot nitric acid; heat, shock, friction, strong oxidizers;
or ignition sources may cause explosions. | [Description]
De scription: Hafnium is a refractory metal which occurs innature in zirconium minerals. Molecular weight= 178.49;Specific gravity (H2O:1)= 13.31; Boiling point = 4602℃; .Freezing/Melting point = 2227℃; Vapor pressure= 1 X .10~4 mmHg at 20℃. Insoluble in water. | [Waste Disposal]
Recovery. Consider recycling,
otherwise, this chemical must be disposed of in compliance
with existing federal and local regulations. | [Isotopes]
There are 44 known isotopes for hafnium. Five are stable and one of the unstableisotopes has such a long half-life (Hf-174 with a 2.0×10+15 years) that it is includedas contributing 0.16% to the amount of hafnium found in the Earth’s crust. The percentagecontributions of the 5 stable isotopes to the element’s natural existence on Earth areas follows: Hf-176 = 5.26%, Hf-177 = 18.60%, Hf-178 = 27.28%, Hf-179 = 13.62%,and Hf-180 = 35.08%. | [Origin of Name]
Named after Hafnia, the Latin name for the city of Copenhagen, Denmark. | [Occurrence]
Hafnium is the 47th most abundant element on Earth. Thus, it is more abundant thaneither gold or silver. Because hafnium and zirconium are always found together in nature, bothmetals are refined and produced by the Kroll process. Pure samples of either hafnium or zirconiumare almost impossible to separate by the Kroll or other refining processes. Baddeleyite(ZrO2), a zirconium ore, and zircon (ZrSiO4) are treated with chlorine along with a carboncatalyst that produces a mixture of zirconium and hafnium tetrachlorides. These are reducedby using sodium or magnesium, resulting in the production of both metals. The molten metalsare separated by the process known as fractionation, which depends on their different meltingpoints and densities. As the mixture of the two metals cools during the fractionation process,the denser solidified hafnium sinks to the bottom of the vessel while the less dense zirconium(with a higher melting point than hafnium) floats on top. | [Characteristics]
As the first element in the third series of the transition elements, hafnium’s atomic number(72Hf ) follows the lanthanide series of rare-earths. The lanthanide series is separated out ofthe normal position of sequenced atomic numbers and is placed below the third series on theperiodic table (57La to 71Li). This rearrangement of the table allowed the positioning of elementsof the third series within groups more related to similar chemical and physical characteristics—for example, the triads of Ti, Zr, and Hf; V, Nb, and Ta; and Cu, Ag, and Au. | [Definition]
hafnium: Symbol Hf. A silvery lustrousmetallic transition element;a.n. 72; r.a.m. 178.49; r.d. 13.3; m.p.2227±20°C; b.p. 4602°C. The elementis found with zirconium and is extractedby formation of the chlorideand reduction by the Kroll process. Itis used in tungsten alloys in filamentsand electrodes and as a neutron absorber.The metal forms a passiveoxide layer in air. Most of its compoundsare hafnium(IV) complexes;less stable hafnium(III) complexesalso exist. The element was first reportedby Urbain in 1911, and its existencewas finally established by Dirk Coster (1889–1950) and Georgede Hevesey (1885–1966) in 1923. | [Hazard]
Although the metal hafnium is not harmful, its powder and dust are both toxic if inhaledand explosive even when wet. | [Flammability and Explosibility]
Highlyflammable | [Industrial uses]
Pure hafnium is a lustrous, silvery metal that is not so ductile nor so easily worked as zirconium; nevertheless, hafnium can be hot- and cold-rolled on the same equipment and with similar techniques as those used for zirconium. All zirconium chemicals and alloys may contain some hafnium, and hafnium metal usually contains about 2% zirconium.The metal has a closepacked hexagonal structure. The electric conductivity is about 6% that of copper. It has excellent resistance to a wide range of corrosive environments.
Because of the startling similarity in their chemical properties, zirconium and hafnium always occur together in nature. In their respective ability to absorb neutrons, however, they differ greatly, and this difference has led to their use in surprisingly different ways in nuclear reactors. Zirconium, with a low neutron-absorption cross section (0.18 barn), is highly desirable as a structural material in water-cooled nuclear reactor cores. Hafnium, on the other hand, because of its high neutron-absorption cross section (105 barns), can be used as a neutron-absorbing control material in the same nuclear reactor cores. Thus, the two elements, which occur together so intimately in nature that they are very difficult to separate, are used as individual and important but contrasting components in the cores of nuclear reactors. | [storage]
Color Code- -Yellow Stripe (dry powder is a strong reducing agent): Reactivity Hazard; Store separately in anarea isolated from flammables, combustibles, or other yellow coded materials. Prior to working with this chemical youshould be trained on its proper handling and storage. Store intightly closed containers in a cool, well-ventilated area. |
| Safety Data | Back Directory | [Hazard Codes ]
F,Xn | [Risk Statements ]
R11:Highly Flammable.
R20/21/22:Harmful by inhalation, in contact with skin and if swallowed . | [Safety Statements ]
S9:Keep container in a well-ventilated place .
S16:Keep away from sources of ignition-No smoking .
S26:In case of contact with eyes, rinse immediately with plenty of water and seek medical advice .
S27:Take off immediately all contaminated clothing .
S33:Take precautionary measures against static discharges .
S36:Wear suitable protective clothing .
S36/37/39:Wear suitable protective clothing, gloves and eye/face protection . | [RIDADR ]
UN 3178 4.1/PG 3
| [WGK Germany ]
-
| [RTECS ]
MG4600000
| [TSCA ]
Yes | [HS Code ]
3822 00 00 | [HazardClass ]
8 | [PackingGroup ]
III | [Hazardous Substances Data]
7440-58-6(Hazardous Substances Data) | [IDLA]
50 mg Hf/m3 |
| Questions And Answer | Back Directory | [History, Occurrence and Uses]
Hafnium was discovered in 1922 by Coster and deHevesy. They named it for Hafnia, the Latin word for Copenhagen. It is found in all zirconium ores, such as zircon, (ZrSiO4) and baddeleyite (ZrO2). It occurs in the earth’s crust at about 3 mg/kg. Its average concentration in sea water is 7 ng/L.
Hafnium is used in control rods for nuclear reactors. It has high resistance to radiation and also very high corrosion resistance. Another major application is in alloys with other refractory metals, such as, tungsten, niobium and tantalum.
| [Chemical Properties]
Hafnium is a lustrous silvery, ductile metal typically found in the 4+ oxidation state. It is poorly soluble in water as a pure metal. It is relatively unreactive to alkalis and strong acids, except hydrofluoric acid and is frequently alloyed with iron, niobium, tantalum, and titanium. Pure hafnium power is pyrophoric and may spontaneously ignite in air, especially under conditions of high moisture. Hafnium powder reacts violently with strong oxidizers and strong acids (Pohanish, 2011). When heated to around 200 °C, hafnium metal may react with several period 2 inorganic elements as well as silicone and sulfur. Hafnium oxide (HfO2) is poorly soluble in water and is a refractory compound, which is highly resistant to corrosion. With halogens, it may react to form tetrahalides. | [Physical Properties]
Occurs as a close-packed hexagonal alpha-form and a body-centered cubic beta modification; electrical resistivity 35.5 microhm-cm at 20°C; magnetic susceptibility 0.42x10–6 emu/g at 25°C; thermal neutron absorption cross section 105 barns/atom; work function 3.5 eV; modulus of elasticity 20x106 psi; tensile strength 58,000 psi at 25°C; insoluble in water, dilute mineral acids and nitric acid at all concentrations; soluble in hydrofluoric acid, concentrated sulfuric acid and aqua regia.
| [Uses]
Hafnium use is limited due to low abundance. The primary use of hafnium is in the nuclear industry, where it is used in fuel rods to regulate fission given its high neutron absorption cross section. Similar to zirconium, hafnium is alloyed with niobium and carbide to produce high temperature refractory materials for furnaces and jet components as well as for plasma cutters. In addition, hafnium oxide is increasingly being used to augment or replace silicone oxidebased microprocessor chips in certain applications as well as in cathodes and capacitors (Field et al., 2011). | [Production]
Hafnium is obtained commercially from mineral zircon, which is zirconium orthosilicate [14940-68-2]. Zircon usually contains hafnium oxide, HfO2, in an amount that ranges between 1 to 2%. Zircon sand is separated from heavy mineral fractions from alluvial deposits by various electrostatic and magnetic separation processes. The sand is then ground and heated with caustic soda at 600°C or with soda ash at 1,000°C, or fused with lime at elevated temperatures to separate silicates.
Alternatively, zircon may be decomposed by heating with chlorine in the presence of coke at 1,100°C. In the caustic fusion process, pulverized fusion cake is washed with water to remove water-soluble sodium silicate and unreacted caustic soda, leaving behind insoluble hydrous zirconium oxide. Hydrous zirconium oxide is soluble in most acids. It is dissolved in hydrochloric acid and filtered to remove unreacted ore and silica. When the chlorination process is applied, the products are zirconium tetrachloride, hafnium tetrachloride, and silicon tetrachloride. Silicon tetrachloride is more volatile than the other two chlorides and, therefore, zirconium tetrachloride and hafnium tetrachloride can be removed from silicon tetrachloride by condensing under controlled heating. The condensed tetrachlorides are dissolved in water and filtered to remove insoluble matter.
| [Reactions]
The chemical properties of hafnium are very much similar to those of zirconium. In aqueous solutions, the metal exists in tetravalent state. The electrode potential for the reaction Hf→ Hf 4+ + 4e¯ is –1.70V. The metal in bulk form does not react with most reagents at ordinary temperatures. However, the powdered metal or hafnium sponge may readily burn in air after ignited with a spark. When heated at 360°C under water pressure, the metal is oxidized to hafnium oxide, forming a thin, protective, surface oxide layer. A similar surface hafnium oxide layer forms in nitric acid, which protects the metal from acid attack.
Reaction with hydrofluoric acid at ordinary temperatures yields hafnium tetrafluoride, HfF4.
Reaction with hydrogen occurs around 700°C. Hafnium absorbs rapidly, forming a hydride which probably has a composition HfH1.86.
Hafnium metal reacts very slowly in concentrated sulfuric acid at ordinary temperatures. At acid concentration above 70% and under boiling conditions, sulfuric acid readily attacks the metal.
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