General Description
Silvery, whitish-gray, malleable, ductile metal. Mp: 1772°C; bp: 2187°C. Density: 21.45 g cm-3 at room conditions (very dense). Also shipped as a finely divided powder (PLATINUM(7440-06-4) black), as a sponge, and as particles deposited on a supporting material such as alumina. Has strong catalytic activity in these forms; finely divided PLATINUM(7440-06-4) can be dangerous to handle in the vicinity of other chemicals on this account. Used PLATINUM(7440-06-4) catalysts are particularly dangerous and can be explosive.
Reactivity Profile
Massive platinum (lump, ingot, etc.) is generally inert. Dissolves readily in aqua regia (mixture of concentrated hydrochloride and concentrated nitric acids). Reacts rapidly with molten alkali metal oxides and peroxides. Reacts with F2 and Cl2 at red heat. Absorbs large volumes of hydrogen when hot. Catalyzes the exothermic oxidation of ammonia by air. Finely divided platinum is incompatible with aluminum, acetone, arsenic, ethane, hydrazine, hydrogen peroxide, lithium, phosphorus, selenium, tellurium and many fluorides. Explosion can occur upon contact with hydrogen peroxide. Platinum black, sponge and supported catalysts have strong catalytic activity; can be dangerous to handle in the vicinity of other chemicals on this account. Used platinum catalysts are particularly dangerous and can cause explosions. Ethanol or methanol can ignite on contact with a platinum-black catalyst. (Urben 1794).
Potential Exposure
Platinum and its alloys have high electrical conductivity and excellent catalytic properties. They are used in relays, contacts and tubes in electronic equipment, in spark plug electrodes for aircraft; and windings in high-temperature electrical furnaces. Platinum alloys are used for standards for weight, length, and temperature measurement. Platinum and platinum catalysts, for example, hexachloroplatinic acid and H2PtCl6, are widely used in the chemical industry in persulfuric, nitric, and sulfuric acid production, in the synthesis of organic compounds and vitamins, and for producing higher octane gasoline. They are coming into use in catalyst systems for control of exhaust pollutants from automobiles. They are used in the equipment for handling molten glass and manufacturing fibrous glass; in laboratory, medical, and dental apparatus; in electroplating; in photography; in jewelry; and in X-ray fluorescent screens. Because platinum complexes are used as antitumor agents, the potential for carcinogenic activity is present; tests to clarify this aspect should be conducted. While low levels of emissions of platinum particulate have been observed from some catalyst-equipped automobiles, the major potential source of Pt is from the disposal of spent catalysts.
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, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When chloroplatinic acid has been swallowed, get medical attention. If victim is conscious, administer water, or milk. Do not induce vomiting.
Shipping
UN3089 Metal powders, flammable, n.o.s., Hazard Class: 4.1; Labels: 4.1-Flammable solid.
Incompatibilities
Dust or powder may form explosive mixture with air. Platinum metal is incompatible with aluminum; acetone, arsenic, ethane, hydrazine, hydrogen peroxide; lithium, phosphorus, selenium, tellurium, various fluorides.
Waste Disposal
Catalyst disposal is expected to be the largest contributor of Pt to the environment. The value of the metal would help to offset the cost of reclaiming the Pt from discarded catalysts. If direct vehicular emissions of Pt are found to be significant, particulate taps, which are available at reasonable cost, may provide a technological solution. In any event, recovery and recycling is the preferred technique for both health and economic reasons. Details of platinum recovery and recycling from plating wastes, platinum metal refinery effluents; spent catalysts and precious metals scrap have been published.
Physical properties
Platinum is classed by tradition and commercial usefulness as a precious metal that is soft,dense, dull, and silvery-white in color, and it is both malleable and ductile and can be formedinto many shapes. Platinum is considered part of the “precious” metals group that includesgold, silver, iridium, and palladium. It is noncorrosive at room temperature and is not solublein any acid except aqua regia. It does not oxidize in air, which is the reason that it is foundin its elemental metallic form in nature. Its melting point is 1,772°C, its boiling point is3,827°C, and its density is 195.09g/cm3.
Isotopes
There are a total of 43 isotopes for platinum. Five of these are stable, andanother has such a long half-life that it is considered practically stable (Pt-190 with ahalf-life of 6.5×10+11 years). Pt-190 contributes just 0.014% to the proportion of platinumfound on Earth. The stable isotopes and their contributions to platinum’s existenceon Earth are as follows: Pt-192 = 0.782%, Pt-194 = 32.967%, Pt-195 = 33.832%, Pt-196 = 25.242%, and Pt-198 = 7.163%. All the other isotopes are radioactive and areproduced artificially. They have half-lives ranging from a few microseconds to minutes tohours, and one has a half-life of 50 years (Pt-193).
Origin of Name
The name “platinum” is derived from the Spanish word platina, which
means “silver.”
Occurrence
Platinum is the 75th most abundant element and, unlike many elements, is found in itspure elemental form in nature, as are deposits of silver and gold. Platinum is widely distributedover the Earth and is mined mainly in the Ural Mountains in Russia and in South Africa,Alaska, the western United States, Columbia in South America, and Ontario in Canada.When found in the mineral sperrylite (PtAs2), it is dissolved with aqua regia to form a precipitatecalled “sponge” that is then converted into platinum metal. It is also recovered as aby-product of nickel mining, mainly in Ontario, Canada.
Characteristics
Platinum is the main metal in the platinum group, which consists of metals in both period5 and period 6. They are ruthenium (Ru), rhodium (Ro), and palladium (Pd) in period 5 andosmium (Os), iridium (Ir), and platinum (Pt) in period 6. All six of these metals share someof the same physical and chemical properties. Also, the other metals in the group are usuallyfound in platinum ore deposits.
Platinum can absorb great quantities of hydrogen gas, which makes it useful as a catalystin industry to speed up chemical reactions.
Definition
A silvery-white
malleable ductile transition metal. It occurs
naturally in Australia and Canada, either
free or in association with other platinum
metals. It is resistant to oxidation and is not attacked by acids (except aqua regia)
or alkalis. Platinum is used as a catalyst for
ammonia oxidation (to make nitric acid)
and in catalytic converters. It is also used in
jewelry.
Symbol: Pt; m.p. 1772°C; b.p. 3830 ±
100°C; r.d. 21.45 (20°C); p.n. 78; r.a.m.
195.08.
Definition
platinum: Symbol Pt. A silverywhite metallic transition element(see also platinum metals); a.n. 78;r.a.m. 195.09; r.d. 21.45; m.p. 1772°C;b.p. 3827±100°C. It occurs in somenickel and copper ores and is alsofound native in some deposits. Themain source is the anode sludge obtainedin copper–nickel refining. Theelement is used in jewellery, laboratoryapparatus (e.g. thermocouples,electrodes, etc.), electrical contacts,and in certain alloys (e.g. with iridium or rhodium). It is also a hydrogenationcatalyst. The elementdoes not oxidize nor dissolve inhydrochloric acid. Most of its compoundsare platinum(II) orplatinum(IV) complexes.
Production Methods
Platinum is obtained mainly from copper and nickel ores, and
platinum alloys and by recovery from the catalyst and other
waste. The main stages of platinum production include
extraction of the precious metal concentrate from the ore followed by separation through a complex refining process,
during which the concentrate is dissolved in aqua regia, and
the platinum is precipitated in the form of ammonium(IV)
hexachloroplatinate. The precipitate is then calcinated at
600–700 °C to give platinum sponge, which is then hardened
by melting at high temperatures, such as in the electric arc.
The resultant gray platinum sponge contains 99.95–99.9%
pure metal. Another method of platinum production involves
its reduction to metal from the aqueous platinum salts by
zinc, magnesium, iron, or aluminum. Similar procedures are
used to recover platinum from the catalytic converters and
other waste. The hexachloroplatinic(IV) acid produced by
treating platinum with aqua regia is an important chemical
platinum compound used to obtain various platinum
salts.
Hazard
Fine platinum powder may explode if near an open flame. Because platinum is rather inertin its elemental metallic form, it is not poisonous to humans, but some of its compounds,particularly its soluble salts, are toxic if inhaled or ingested.
Health Hazard
Exposure to the complex salts of
platinum, especially ammonium hexachloroplatinate and ammonium tetrachloroplatinate,
but not elemental platinum, may cause skin
sensitization and a progressive allergic reaction
that may lead to pronounced asthmatic
symptoms.
The signs and symptoms of hypersensitivity include urticaria, contact dermatitis of the
skin, and respiratory disorders ranging from
sneezing, shortness of breath, and cyanosis to
severe asthma. The latency period from the
first contact with platinum to the occurrence of
the first symptoms varies from a few weeks to
several years.
Flammability and Explosibility
Nonflammable
Environmental Fate
Inhalation of industrial platinum compounds may be
a problem. The general population is exposed to platinum by
the dermal route, especially from jewelry. The oral route is not
significant because the absorption is very poor.
Platinum can enter the environment through automobile
emissions from the platinum-containing catalytic converter.Relatively high levels of platinum can be found along congested
roadways. A number of chemotherapeutic agents
contain platinum and thus their disposal can lead to environmental
contamination. In industrialized regions, relatively
high concentrations can be found in waterway sediments.
Organic matter binds to the metal. In soil, mobility depends on
pH, redox potential, and chloride concentration. Platinum will
likely only mobilize under highly acidic conditions or in soil
water with high chloride content. Some platinum (IV)
complexes, in the presence of platinum (II), may undergo
methylation by microorganisms.
Toxicity evaluation
While the metal itself is systemically of little concern, its salts
are very toxic. The cis-platinum compounds can react with
disulfides and amino groups and form adducts with some bases in nucleic acids. Platinum compounds inhibit a few
enzymes, including leucine aminopeptidase, and the hydrogenases
of malate, alcohol, and lactate. Cisplatin can form
crosslinks between strands of DNA.
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