پالادیم

از ویکی‌پدیا، دانشنامهٔ آزاد
پرش به ناوبری پرش به جستجو
فارسیEnglish
رودیمپالادیمنقره
Ni

Pd

Pt
ظاهر
نقرهy white metallic
ویژگی‌های کلی
نام، نماد، عدد پالادیم، Pd،‏ 46
تلفظ به انگلیسی ‎/pəˈldiəm/‎
pə-LAY-dee-əm
نام گروهی برای عناصر مشابه فلزات واسطه
گروه، دوره، بلوک ۱۰، ۵، d
جرم اتمی استاندارد 106.42 گرم بر مول
آرایش الکترونی [Kr] 4d10
الکترون به لایه 2, 8, 18, 18
ویژگی‌های فیزیکی
حالت جامد
چگالی (نزدیک به دمای اتاق) 12.023 g·cm−۳
چگالی مایع در نقطه ذوب 10.38 g·cm−۳
نقطه ذوب 1828.05 K،‎ 1554.9 °C،‎ 2830.82 °F
نقطه جوش 3236 K،‎ 2963 °C،‎ 5365 °F
گرمای هم‌جوشی 16.74 کیلوژول بر مول
گرمای تبخیر 362 کیلوژول بر مول
ظرفیت گرمایی 25.98 کیلوژول بر مول
فشار بخار
فشار (پاسکال) ۱ ۱۰ ۱۰۰ ۱k ۱۰k ۱۰۰k
دما (کلوین) 1721 1897 2117 2395 2753 3234
ویژگی‌های اتمی
وضعیت اکسید شدن 0, +1, +2, +4, +6
(mildly basic oxide)
الکترونگاتیوی 2.20 (مقیاس پاولینگ)
انرژی‌های یونش نخستین: 804.4 کیلوژول بر مول
دومین: 1870 کیلوژول بر مول
سومین: 3177 کیلوژول بر مول
شعاع اتمی 137 pm
شعاع کووالانسی 139±6 pm
شعاع واندروالانسی 163 pm
متفرقه
ساختار کریستالی face-centered cubic
مغناطیس پارامغناطیس[۱]
مقاومت ویژه الکتریکی (20 °C) 105.4 nΩ·m
رسانایی گرمایی (300 K) 71.8 W·m−1·K−1
انبساط گرمایی (25 °C) 11.8 µm·m−1·K−1
سرعت صوت (سیم نازک) (20 °C) 3070 m/s
مدول یانگ 121 GPa
مدول برشی 44 GPa
مدول حجمی 180 GPa
نسبت پواسون 0.39
سختی موس 4.75
سختی ویکر 461 MPa
سختی برینل 37.3 MPa
عدد کاس 7440-05-3
پایدارترین ایزوتوپ‌ها
مقاله اصلی ایزوتوپ‌های پالادیم
ایزوتوپ NA نیمه‌عمر DM DE (MeV) DP
100Pd syn 3.63 d ε - 100Rh
γ 0.084, 0.074,
0.126
-
102Pd 1.02% 102Pd ایزوتوپ پایدار است که 56 نوترون دارد
103Pd syn 16.991 d ε - 103Rh
104Pd 11.14% 104Pd ایزوتوپ پایدار است که 58 نوترون دارد
105Pd 22.33% 105Pd ایزوتوپ پایدار است که 59 نوترون دارد
106Pd 27.33% 106Pd ایزوتوپ پایدار است که 60 نوترون دارد
107Pd ایزوتوپ پرتوزای ناچیز 6.5×106 y β 0.033 107Ag
108Pd 26.46% 108Pd ایزوتوپ پایدار است که 62 نوترون دارد
110Pd 11.72% 110Pd ایزوتوپ پایدار است که 64 نوترون دارد

پالادیوم یا پالادیم از عنصرهای شیمیایی جدول تناوبی است. نشانه کوتاه آن Pd و عدد اتمی آن ۴۶ است، و یکی از فلزات کمیاب است و به رنگ نقره‌ای و سفید می‌باشد. پالادیوم از فلزات گروه پلاتین است و در مقایسه با سایر فلزات این گروه کمترین چگالی و پائینترین نقطه ذوب را دارد. این فلز کمیاب بیشتر از معادن مس و نیکل بدست می‌آید.

تولید جهانی پالادیم از معادن در سال ۲۰۰۶ حدود ۲۲۲ تن بوده و بیشتر آن برای تهیه مبدل‌های کاتالیست در صنعت خودروسازی استفاده شده‌است که گازهای سمی خروجی از اگزوز را به ترکیبات بی‌خطر یا کم‌خطر تبدیل می‌کنند. از این فلز در صنایع الکترونیک، پزشکی (مثل نوارهای تست قند خون)، دندانپزشکی، تلخیص هیدروژن، صنایع شیمیایی، هواپیماسازی و جواهرسازی (مثل تولید طلای سفید) نیز استفاده می‌شود. این فلز همچنین نقش مهمی در تولید نوعی از پیلهای سوختی دارد که هیدروژن و اکسیژن را ترکیب کرده تا الکتریسیته، گرما و آب تولید کنند.

پالادیم یکی از گرانترین فلزات دنیاست و قیمت هر اونس آن در سال ۲۰۱۴ بیش از ۸۰۰ دلار (نزدیک به ۳۰ هزار دلار برای هر کیلوگرم) بوده‌است. بیشتر پالادیم دنیا در دو کشور روسیه و آفریقای جنوبی تولید می‌شود ضمن اینکه بازیافت محصولات حاوی پالادیم نیز به ویژه مبدل‌های کاتالیست یکی از منابع عمده تولید این فلز است.

تاریخچه[ویرایش]

پالادیوم در سال ۱۸۰۳ توسط ویلیام هاید والاستون کشف شد. این عنصر دو سال بعد از کشف سیارک پالاس و به نام آن نامگذاری شد، که نام این سیارک هم برگرفته از الهه یونانی خرد، آتنا ملقب به پالاس است. والاستون این عنصر را در یک معدن پلاتین در آمریکای جنوبی کشف کرد. او این عمل را با حل کردن مواد دریافت شده از معدن در تیزاب سلطانی و خنثی سازی محلول با اضافه کردن هیدروکسید سدیم که با اضافه کردن آمونیوم کلرید باعث ته‌نشین شدن نمک آمونیوم کلرو پلاتینات میشد و با اضافه کردن سیانید جیوه باعث شکل‌گیری پالادیوم سیانید می‌شد و در آخر با گرم کردن ترکیب بدست آمده، فلز پالادیوم را بدست آورد.

روزگاری ترکیب کلریدپالادیوم برای درمان مرض سل به میزان ۰٫۰۶۵ گرم در روز تجویز می‌شد. این ترکیب، عوارض جانبی زیادی داشت و بعداً داروهای مؤثر دیگر جایگزین آن شدند.

پیدایش[ویرایش]

پالادیوم هم به صورت فلز آزاد و هم به صورت آلیاژ با طلا و پلاتین و دیگر فلزات این گروه در محل کوه‌های اورال استرالیا، اتیوپی و آمریکای شمالی و جنوبی یافت می‌شود. با این حال، اکثر پالادیوم مصرفی به دلیل صرفه اقتصادی از معادن نیکل و مس در آفریقای جنوبی و انتاریوی کانادا استخراج می‌شود، چرا که حجم بالای فلزات تولید این معادن عمل دریافت پالادیوم را به‌صرفه می‌کند.

ویژگی‌های قابل توجه[ویرایش]

پالادیوم در مجاورت هوا سیاه نمی‌شود. این فلز با چگالی اندک خود، پایین‌ترین نقطه ذوب را در میان فلزات هم گروه پلاتینیوم دارد. این فلز در زمانی که به آن حرارت داده شود، به میزان زیاده کشیده و نرم شده، در دمای سخت سفت و محکم می‌شود. پالادیوم به‌شدت با ترکیبات گوگردی و اسید نیتریک ترکیب شده، به‌آرامی در اسید هیدروکلریک حل می‌شود. همچنین این فلز در دماهای معمولی با اکسیژن ترکیب نمی‌شود.

این فلز به طرز بسیار غیرمعمول و عجیب خاصیت جذب هیدروژن را تا ۹۰۰ برابر حجم خود در شرایط مناسب (دمای ۸۰ درجه سانتیگراد و فشار ۱ اتمسفر) دارد.[۲] به نظر می‌رسد که احتمالاً هیدرید پالادیوم را شکل می‌دهد: pd2H. اما هنوز ترکیب شیمیایی واقعی آن آشکار نیست.

حالتهای معمولی اکسیداسیون پالادیوم +۲، +۳ و +۴ می‌باشد. اخیراً ترکیبات پالادیوم که در آن، این عنصر اکسیداسیون +۶ دارد هم به وجود آمد.

کاربردها[ویرایش]

پالادیوم، کاتالیزورهای خوبی را شکل داده، مخصوصاً در عمل تصفیه نفت، سرعت هیدروژن‌گیری و هیدروژن‌زدایی (Hydrogenation and Dehydrogenation) را زیاد می‌کند. همچنین آلیاژ آن، در جواهرسازی استفاده می‌شود.

طلای سفید، آلیاژی از طلا بوده که با اضافه کردن پالادیوم، رنگ خود را از دست می‌دهد.

پالادیوم نیز همانند طلا می‌تواند به ورقه‌های نازک تبدیل شود.

هیدروژن به‌راحتی در پالادیوم گرم شده منتشر می‌شود که در خالص‌سازی گازها کاربرد دارد.

در تجهیزات و سیستم‌های سوییچینگ مخابراتی از پالادیوم استفاده می‌شود.

پالادیوم همچنین در دندانپزشکی، ساعت سازی و ساخت ابزار جراحی و اتصالات الکتریکی کاربرد دارد.

ایزوتوپها[ویرایش]

پالادیوم طبیعی از شش ایزوتوپ تشکیل شده‌است. پایدارترین ایزوتوپ‌های رادیو اکتیوی Pd-107 با نیمه عمر ۶٫۵ میلیون سال، Pd-103 با نیمه عمر ۱۷ روز و Pd-100 با نیمه عمر ۳٫۶۳ روز روز می‌باشند. ۱۸ ایزوتوپ رادیواکتیوی دیگر از طریق وزن اتمی شان طبقه‌بندی می‌شوند. اکثر آن‌ها به غیر از Pd-101 که نیمه عمرش ۸٫۴۷ ساعت و Pd-109 که نیمه عمرش ۱۳٫۷ ساعت و Pd-112 که نیمه عمرش ۲۱ ساعت است، بقیه نیمه عمری کمتر از نیم ساعت دارند.

ویژگی‌های فیزیکی[ویرایش]

تولید جهانی پالادیم در سال ۲۰۰۵
  • عدد اتمی: ۴۶
  • جرم اتمی: ۱۰۶٫۴
  • نقطه ذوب: C° ۱۵۵۴٫۹
  • نقطه جوش: C° ۲۹۶۳
  • ظرفیت: ۱
  • رنگ: سفید نقره‌ای متالیک

منابع[ویرایش]

  1. Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
  2. "palladium (Pd)". Encyclopædia Britannica. Retrieved 16 May 2014.

پیوند به بیرون[ویرایش]

Palladium,  46Pd
Palladium (46 Pd).jpg
Palladium
Pronunciation/pəˈldiəm/ (pə-LAY-dee-əm)
Appearancesilvery white
Standard atomic weight Ar, std(Pd)106.42(1)[1]
Palladium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Ni

Pd

Pt
rhodiumpalladiumsilver
Atomic number (Z)46
Groupgroup 10
Periodperiod 5
Blockd-block
Element category  Transition metal
Electron configuration[Kr] 4d10
Electrons per shell
2, 8, 18, 18
Physical properties
Phase at STPsolid
Melting point1828.05 K ​(1554.9 °C, ​2830.82 °F)
Boiling point3236 K ​(2963 °C, ​5365 °F)
Density (near r.t.)12.023 g/cm3
when liquid (at m.p.)10.38 g/cm3
Heat of fusion16.74 kJ/mol
Heat of vaporization358 kJ/mol
Molar heat capacity25.98 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1721 1897 2117 2395 2753 3234
Atomic properties
Oxidation states0, +1, +2, +3, +4 (a mildly basic oxide)
ElectronegativityPauling scale: 2.20
Ionization energies
  • 1st: 804.4 kJ/mol
  • 2nd: 1870 kJ/mol
  • 3rd: 3177 kJ/mol
Atomic radiusempirical: 137 pm
Covalent radius139±6 pm
Van der Waals radius163 pm
Color lines in a spectral range
Spectral lines of palladium
Other properties
Natural occurrenceprimordial
Crystal structureface-centered cubic (fcc)
Face-centered cubic crystal structure for palladium
Speed of sound thin rod3070 m/s (at 20 °C)
Thermal expansion11.8 µm/(m·K) (at 25 °C)
Thermal conductivity71.8 W/(m·K)
Electrical resistivity105.4 nΩ·m (at 20 °C)
Magnetic orderingparamagnetic[2]
Magnetic susceptibility+567.4·10−6 cm3/mol (288 K)[3]
Young's modulus121 GPa
Shear modulus44 GPa
Bulk modulus180 GPa
Poisson ratio0.39
Mohs hardness4.75
Vickers hardness400–600 MPa
Brinell hardness320–610 MPa
CAS Number7440-05-3
History
Namingafter asteroid Pallas, itself named after Pallas Athena
Discovery and first isolationWilliam Hyde Wollaston (1802)
Main isotopes of palladium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
100Pd syn 3.63 d ε 100Rh
γ
102Pd 1.02% stable
103Pd syn 16.991 d ε 103Rh
104Pd 11.14% stable
105Pd 22.33% stable
106Pd 27.33% stable
107Pd trace 6.5×106 y β 107Ag
108Pd 26.46% stable
110Pd 11.72% stable
| references

Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas. Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.

More than half the supply of palladium and its congener platinum is used in catalytic converters, which convert as much as 90% of the harmful gases in automobile exhaust (hydrocarbons, carbon monoxide, and nitrogen dioxide) into less noxious substances (nitrogen, carbon dioxide and water vapor). Palladium is also used in electronics, dentistry, medicine, hydrogen purification, chemical applications, groundwater treatment, and jewelry. Palladium is a key component of fuel cells, which react hydrogen with oxygen to produce electricity, heat, and water.

Ore deposits of palladium and other PGMs are rare. The most extensive deposits have been found in the norite belt of the Bushveld Igneous Complex covering the Transvaal Basin in South Africa, the Stillwater Complex in Montana, United States; the Sudbury Basin and Thunder Bay District of Ontario, Canada, and the Norilsk Complex in Russia. Recycling is also a source, mostly from scrapped catalytic converters. The numerous applications and limited supply sources result in considerable investment interest.

Characteristics

Palladium belongs to group 10 in the periodic table, but the configuration in the outermost electrons are in accordance with Hund's rule. Electrons in the s orbital[clarification needed] migrate to fill the d orbitals because they have less energy.[clarification needed]

Z Element No. of electrons/shell
28 nickel 2, 8, 16, 2 (or 2, 8, 17, 1)
46 palladium 2, 8, 18, 18, 0
78 platinum 2, 8, 18, 32, 17, 1
110 darmstadtium 2, 8, 18, 32, 32, 16, 2 (predicted)

This 5s0 configuration, unique in period 5, makes palladium the heaviest element having only one incomplete electron shell, with all shells above it empty.

Palladium is a soft silver-white metal that resembles platinum. It is the least dense and has the lowest melting point of the platinum group metals. It is soft and ductile when annealed and is greatly increased in strength and hardness when cold-worked. Palladium dissolves slowly in concentrated nitric acid, in hot, concentrated sulfuric acid, and when finely ground, in hydrochloric acid.[4] It dissolves readily at room temperature in aqua regia.

Palladium does not react with oxygen at standard temperature (and thus does not tarnish in air). Palladium heated to 800 °C will produce a layer of palladium(II) oxide (PdO). It may slowly develop a slight brownish coloration over time, likely due to the formation of a surface layer of its monoxide.

Palladium films with defects produced by alpha particle bombardment at low temperature exhibit superconductivity having Tc=3.2 K.[5]

Isotopes

Naturally occurring palladium is composed of seven isotopes, six of which are stable. The most stable radioisotopes are 107Pd with a half-life of 6.5 million years (found in nature), 103Pd with 17 days, and 100Pd with 3.63 days. Eighteen other radioisotopes have been characterized with atomic weights ranging from 90.94948(64) u (91Pd) to 122.93426(64) u (123Pd).[6] These have half-lives of less than thirty minutes, except 101Pd (half-life: 8.47 hours), 109Pd (half-life: 13.7 hours), and 112Pd (half-life: 21 hours).[7]

For isotopes with atomic mass unit values less than that of the most abundant stable isotope, 106Pd, the primary decay mode is electron capture with the primary decay product being rhodium. The primary mode of decay for those isotopes of Pd with atomic mass greater than 106 is beta decay with the primary product of this decay being silver.[7]

Radiogenic 107Ag is a decay product of 107Pd and was first discovered in 1978[8] in the Santa Clara[9] meteorite of 1976. The discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. 107Pd versus Ag correlations observed in bodies, which have been melted since accretion of the solar system, must reflect the presence of short-lived nuclides in the early solar system.[10]

Compounds

Palladium compounds primarily exist in the 0 and +2 oxidation state. Other less common states are also recognized. Generally the compounds of palladium are more similar to those of platinum than those of any other element.

Alpha-palladium(II)-chloride-xtal-3D-balls.png
Pd6Cl12-from-xtal-1996-CM-3D-ellipsoids.png
Structure of α-PdCl2
Structure of β-PdCl2

Palladium(II)

Palladium(II) chloride is the principal starting material for other palladium compounds. It arises by the reaction of palladium with chlorine. It is used to prepare heterogeneous palladium catalysts such as palladium on barium sulfate, palladium on carbon, and palladium chloride on carbon.[11] Solutions of PdCl2 in nitric acid react with acetic acid to give palladium(II) acetate, also a versatile reagent. PdCl2 reacts with ligands (L) to give square planar complexes of the type PdCl2L2. One example of such complexes is the benzonitrile derivative PdX2(PhCN)2.[12][13]

PdCl2 + 2 L → PdCl2L2 (L = PhCN, PPh3, NH3, etc)

The complex bis(triphenylphosphine)palladium(II) dichloride is a useful catalyst.[14]

Palladium(0)

Palladium forms a range of zerovalent complexes with the formula PdL4, PdL3 and PdL2. For example, reduction of a mixture of PdCl2(PPh3)2 and PPh3 gives tetrakis(triphenylphosphine)palladium(0):[15]

2 PdCl2(PPh3)2 + 4 PPh3 + 5 N2H4 → 2 Pd(PPh3)4 + N2 + 4 N2H5+Cl

Another major palladium(0) complex, tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3), is prepared by reducing sodium tetrachloropalladate in the presence of dibenzylideneacetone.[16]

Palladium(0), as well as palladium(II), are catalysts in coupling reactions, as has been recognized by the 2010 Nobel Prize in Chemistry to Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki. Such reactions are widely practiced for the synthesis of fine chemicals. Prominent coupling reactions include the Heck, Suzuki, Sonogashira coupling, Stille reactions, and the Kumada coupling. Palladium(II) acetate, tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4, and tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3) serve either as catalysts or precatalysts.[17]

Other oxidation states

Although Pd(IV) compounds are comparatively rare, one example is sodium hexachloropalladate(IV), Na2[PdCl6]. A few compounds of palladium(III) are also known.[18] Palladium(VI) was claimed in 2002,[19][20] but subsequently disproven.[21][22]

Mixed valence palladium complexes exist, e.g. Pd4(CO)4(OAc)4Pd(acac)2 forms an infinite Pd chain structure, with alternatively interconnected Pd4(CO)4(OAc)4 and Pd(acac)2 units.[23]

History

William Hyde Wollaston noted the discovery of a new noble metal in July 1802 in his lab book and named it palladium in August of the same year. Wollaston purified a quantity of the material and offered it, without naming the discoverer, in a small shop in Soho in April 1803. After harsh criticism from Richard Chenevix that palladium is an alloy of platinum and mercury, Wollaston anonymously offered a reward of £20 for 20 grains of synthetic palladium alloy.[24] Chenevix received the Copley Medal in 1803 after he published his experiments on palladium. Wollaston published the discovery of rhodium in 1804 and mentions some of his work on palladium.[25][26] He disclosed that he was the discoverer of palladium in a publication in 1805.[24][27]

It was named by Wollaston in 1802 after the asteroid 2 Pallas, which had been discovered two months earlier.[4] Wollaston found palladium in crude platinum ore from South America by dissolving the ore in aqua regia, neutralizing the solution with sodium hydroxide, and precipitating platinum as ammonium chloroplatinate with ammonium chloride. He added mercuric cyanide to form the compound palladium(II) cyanide, which was heated to extract palladium metal.[25]

Palladium chloride was at one time prescribed as a tuberculosis treatment at the rate of 0.065 g per day (approximately one milligram per kilogram of body weight). This treatment had many negative side-effects, and was later replaced by more effective drugs.[28]

Most palladium is used for catalytic converters in the automobile industry.[29] In the run up to year 2000, the Russian supply of palladium to the global market was repeatedly delayed and disrupted; for political reasons, the export quota was not granted on time.[30] The ensuing market panic drove the price to an all-time high of $1340 per troy ounce in January 2001.[31] Around that time, the Ford Motor Company, fearing that automobile production would be disrupted by a palladium shortage, stockpiled the metal. When prices fell in early 2001, Ford lost nearly US$1 billion.[32]

World demand for palladium increased from 100 tons in 1990 to nearly 300 tons in 2000. The global production of palladium from mines was 222 tonnes in 2006 according to the United States Geological Survey.[33] Many were concerned about a steady supply of palladium in the wake of Russia's annexation of Crimea, partly as sanctions could hamper Russian palladium exports; any restrictions on Russian palladium exports could have exacerbated what was already expected to be a large palladium deficit in 2014.[34] Those concerns pushed palladium prices to their highest level since 2001.[35] In September 2014 they soared above the $900 per ounce mark. In 2016 however palladium cost around $614 per ounce as Russia managed to maintain stable supplies.[36] In January 2019 palladium futures climbed past $1,344 per ounce for the first time on record, mainly due to the strong demand from the automotive industry.[37]

Occurrence

Palladium output in 2005

As overall mine production of palladium reached 208,000 kilograms in 2016, Russia was the top producer with 82,000 kilograms, followed by South Africa, Canada and the U.S.[38] Russia's company Norilsk Nickel ranks first among the largest palladium producers globally, accounting for 39% of the world’s production.[39]

Palladium can be found as a free metal alloyed with gold and other platinum-group metals in placer deposits of the Ural Mountains, Australia, Ethiopia, North and South America. For the production of palladium, these deposits play only a minor role. The most important commercial sources are nickel-copper deposits found in the Sudbury Basin, Ontario, and the Norilsk–Talnakh deposits in Siberia. The other large deposit is the Merensky Reef platinum group metals deposit within the Bushveld Igneous Complex South Africa. The Stillwater igneous complex of Montana and the Roby zone ore body of the Lac des Îles igneous complex of Ontario are the two other sources of palladium in Canada and the United States.[33][40] Palladium is found in the rare minerals cooperite[41] and polarite.[42] Many more Pd minerals are known, but all of them are very rare.[43]

Palladium is also produced in nuclear fission reactors and can be extracted from spent nuclear fuel (see synthesis of precious metals), though this source for palladium is not used. None of the existing nuclear reprocessing facilities are equipped to extract palladium from the high-level radioactive waste.[44]

Applications

The Soviet 25-rouble commemorative palladium coin is a rare example of the monetary usage of palladium.

The largest use of palladium today is in catalytic converters.[45] Palladium is also used in jewelry, dentistry,[45][46] watch making, blood sugar test strips, aircraft spark plugs, surgical instruments, and electrical contacts.[47] Palladium is also used to make professional transverse (concert or classical) flutes.[48] As a commodity, palladium bullion has ISO currency codes of XPD and 964. Palladium is one of only four metals to have such codes, the others being gold, silver and platinum.[49] Because it adsorbs hydrogen, palladium is a key component of the controversial cold fusion experiments that began in 1989.

Catalysis

When it is finely divided, as with palladium on carbon, palladium forms a versatile catalyst; it speeds heterogeneous catalytic processes like hydrogenation, dehydrogenation, and petroleum cracking. Palladium is also essential to the Lindlar catalyst, also called Lindlar's Palladium.[50] A large number of carbon–carbon bonding reactions in organic chemistry are facilitated by palladium compound catalysts. For example:

(See palladium compounds and palladium-catalyzed coupling reactions.)

When dispersed on conductive materials, palladium is an excellent electrocatalyst for oxidation of primary alcohols in alkaline media.[51] Palladium is also a versatile metal for homogeneous catalysis, used in combination with a broad variety of ligands for highly selective chemical transformations.

In 2010, palladium-catalysed organic reactions were recognized by the Nobel Prize in Chemistry. A 2008 study showed that palladium is an effective catalyst for carbon-fluorine bonds.[52]

Catalytic cycle for Kumada cross coupling reaction, which is widely used in the synthesis of fine chemicals.

Palladium catalysis is primarily employed in organic chemistry and industrial applications, although its use is growing as a tool for synthetic biology; in 2017, effective in vivo catalytic activity of palladium nanoparticles was demonstrated in mammals to treat disease.[53]

Electronics

The second greatest application of palladium in electronics is in multi-layer ceramic capacitors[54] in which palladium (and palladium-silver alloy) is used for electrodes.[45] Palladium (sometimes alloyed with nickel) is used for component and connector plating in consumer electronics[55][56] and in soldering materials. The electronic sector consumed 1.07 million troy ounces (33.2 tonnes) of palladium in 2006, according to a Johnson Matthey report.[57]

Technology

Hydrogen easily diffuses through heated palladium,[4] and membrane reactors with Pd membranes are used in the production of high purity hydrogen.[58] Palladium is used in palladium-hydrogen electrodes in electrochemical studies. Palladium(II) chloride readily catalyzes carbon monoxide gas to carbon dioxide and is useful in carbon monoxide detectors.[59]

Hydrogen storage

Palladium readily adsorbs hydrogen at room temperatures, forming palladium hydride PdHx with x less than 1.[60] While this property is common to many transition metals, palladium has a uniquely high absorption capacity and does not lose its ductility until x approaches 1.[61] This property has been investigated in designing an efficient, inexpensive, and safe hydrogen fuel storage medium, though palladium itself is currently prohibitively expensive for this purpose.[62] The content of hydrogen in palladium can be linked to magnetic susceptibility, which decreases with the increase of hydrogen and becomes zero for PdH0.62. At any higher ratio, the solid solution becomes diamagnetic.[63]

Dentistry

Palladium is used in small amounts (about 0.5%) in some alloys of dental amalgam to decrease corrosion and increase the metallic lustre of the final restoration.[64]

Jewelry

Palladium has been used as a precious metal in jewelry since 1939 as an alternative to platinum in the alloys called "white gold", where the naturally white color of palladium does not require rhodium plating. Palladium is much less dense than platinum. Similar to gold, palladium can be beaten into leaf as thin as 100 nm (​1250,000 in).[4] Unlike platinum, palladium may discolor at temperatures above 400 °C (752 °F)[65] due to oxidation, making it more brittle and thus less suitable for use in jewelry; to prevent this, palladium intended for jewelry is heated under controlled conditions.[citation needed]

Prior to 2004, the principal use of palladium in jewelry was the manufacture of white gold. Palladium is one of the three most popular alloying metals in white gold (nickel and silver can also be used).[45] Palladium-gold is more expensive than nickel-gold, but seldom causes allergic reactions (though certain cross-allergies with nickel may occur).[66]

When platinum became a strategic resource during World War II, many jewelry bands were made out of palladium. Palladium was little used in jewelry because of the technical difficulty of casting. With the casting problem resolved[citation needed] the use of palladium in jewelry increased, originally because platinum increased in price while the price of palladium decreased.[67] In early 2004, when gold and platinum prices rose steeply, China began fabricating volumes of palladium jewelry, consuming 37 tonnes in 2005. Subsequent changes in the relative price of platinum lowered demand for palladium to 17.4 tonnes in 2009.[68][69] Demand for palladium as a catalyst has increased the price of palladium to about 50% higher than that of platinum in January 2019.[70]

In January 2010, hallmarks for palladium were introduced by assay offices in the United Kingdom, and hallmarking became mandatory for all jewelry advertising pure or alloyed palladium. Articles can be marked as 500, 950, or 999 parts of palladium per thousand of the alloy.

Fountain pen nibs made from gold are sometimes plated with palladium when a silver (rather than gold) appearance is desired. Sheaffer has used palladium plating for decades, either as an accent on otherwise gold nibs or covering the gold completely.

Photography

In the platinotype printing process, photographers make fine-art black-and-white prints using platinum or palladium salts. Often used with platinum, palladium provides an alternative to silver.[71]

Toxicity

Palladium
Hazards
GHS pictograms GHS07: Harmful
GHS Signal word Warning
H317
P261, P273, P280, P302+352, P321, P333+313, P363, P501[72]
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
0
0
0

Palladium is a metal with low toxicity as conventionally measured (e.g. LD50). Recent research on the mechanism of palladium toxicity suggests high toxicity if measured on a longer timeframe and at the cellular level in the liver and kidney.[73] Mitochondria appear to have a key role in palladium toxicity via mitochondrial membrane potential collapse and depletion of the cellular glutathione (GSH) level. Until that recent work, it had been thought that palladium was poorly absorbed by the human body when ingested. Plants such as the water hyacinth are killed by low levels of palladium salts, but most other plants tolerate it, although tests show that, at levels above 0.0003%, growth is affected. High doses of palladium could be poisonous; tests on rodents suggest it may be carcinogenic, though until the recent research cited above, no clear evidence indicated that the element harms humans.[74]

Precautions

Like other platinum-group metals, bulk Pd is quite inert. Although contact dermatitis has been reported, data on the effects are limited. It has been shown that people with an allergic reaction to palladium also react to nickel, making it advisable to avoid the use of dental alloys containing palladium on those so allergic.[29][75][76][77][78]

Some palladium is emitted with the exhaust gases of cars with catalytic converters. Between 4 and 108 ng/km of palladium particulate is released by such cars, while the total uptake from food is estimated to be less than 2 µg per person a day. The second possible source of palladium is dental restoration, from which the uptake of palladium is estimated to be less than 15 µg per person per day. People working with palladium or its compounds might have a considerably greater uptake. For soluble compounds such as palladium chloride, 99% is eliminated from the body within 3 days.[29]

The median lethal dose (LD50) of soluble palladium compounds in mice is 200 mg/kg for oral and 5 mg/kg for intravenous administration.[29]

See also

References

  1. ^ Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
  2. ^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  3. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  4. ^ a b c d Hammond, C. R. (2004). "The Elements". Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0485-9.
  5. ^ B. Strizker, Phys. Rev. Lett., 42, 1769 (1979).
  6. ^ "Atomic Weights and Isotopic Compositions for Palladium (NIST)". 23 August 2009. Retrieved 12 November 2009.
  7. ^ a b Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  8. ^ Kelly, W. R.; Gounelle, G. J.; Hutchison, R. (1978). "Evidence for the existence of 107Pd in the early solar system". Geophysical Research Letters. 359 (1787): 1079–1082. Bibcode:2001RSPTA.359.1991R. doi:10.1098/rsta.2001.0893.
  9. ^ "Mexico's Meteorites" (PDF). mexicogemstones.com. Archived from the original (PDF) on 6 May 2006.
  10. ^ Chen, J. H.; Wasserburg, G. J. (1990). "The isotopic composition of Ag in meteorites and the presence of 107Pd in protoplanets". Geochimica et Cosmochimica Acta. 54 (6): 1729–1743. Bibcode:1990GeCoA..54.1729C. doi:10.1016/0016-7037(90)90404-9.
  11. ^ Mozingo, Ralph (1955). "Palladium Catalysts". Organic Syntheses.; Collective Volume, 3, p. 685
  12. ^ Anderson, Gordon K.; Lin, Minren; Sen, Ayusman; Gretz, Efi (1990). Bis(Benzonitrile)Dichloro Complexes of Palladium and Platinum. Inorganic Syntheses. 28. pp. 60–63. doi:10.1002/9780470132593.ch13. ISBN 978-0-470-13259-3.
  13. ^ Zalevskaya, O. A; Vorob'eva, E. G; Dvornikova, I. A; Kuchin, A. V (2008). "Palladium complexes based on optically active terpene derivatives of ethylenediamine". Russian Journal of Coordination Chemistry. 34 (11): 855–857. doi:10.1134/S1070328408110110.
  14. ^ Miyaura, Norio; Suzuki, Akira (1993). "Palladium-catalyzed reaction of 1-alkenylboronates with vinylic halides: (1Z,3E)-1-Phenyl-1,3-octadiene". Organic Syntheses.; Collective Volume, 8, p. 532
  15. ^ Coulson, D. R.; Satek, L. C.; Grim, S. O. (1972). 23. Tetrakis(triphenylphosphine)palladium(0). Inorg. Synth. Inorganic Syntheses. 13. pp. 121–124. doi:10.1002/9780470132449.ch23. ISBN 978-0-470-13244-9.
  16. ^ Takahashi, Y; Ito, Ts; Sakai, S; Ishii, Y (1970). "A novel palladium(0) complex; bis(dibenzylideneacetone)palladium(0)". Journal of the Chemical Society D: Chemical Communications (17): 1065. doi:10.1039/C29700001065.
  17. ^ Crabtree, Robert H. (2009). "Application to Organic Synthesis". The Organometallic Chemistry of the Transition Metals. John Wiley and Sons. p. 392. ISBN 978-0-470-25762-3.
  18. ^ Powers, David C; Ritter, Tobias (2011). "Palladium(III) in Synthesis and Catalysis". Higher Oxidation State Organopalladium and Platinum Chemistry. Topics in Organometallic Chemistry. 35. pp. 129–156. doi:10.1007/978-3-642-17429-2_6. ISBN 978-3-642-17428-5. PMC 3066514. PMID 21461129.
  19. ^ Chen, W; Shimada, S; Tanaka, M (2002). "Synthesis and Structure of Formally Hexavalent Palladium Complexes". Science. 295 (5553): 308–310. Bibcode:2002Sci...295..308C. doi:10.1126/science.1067027. PMID 11786638.
  20. ^ Crabtree, R. H (2002). "CHEMISTRY: A New Oxidation State for Pd?". Science. 295 (5553): 288–289. doi:10.1126/science.1067921. PMID 11786632.
  21. ^ Aullón, G; Lledós, A; Alvarez, S (2002). "Hexakis(silyl)palladium(VI) or palladium(II with eta2-disilane ligands?". Angewandte Chemie (International Ed. In English). 41 (11): 1956–9. doi:10.1002/1521-3773(20020603)41:11<1956::AID-ANIE1956>3.0.CO;2-#. PMID 19750645.
  22. ^ Sherer, E. C; Kinsinger, C. R; Kormos, B. L; Thompson, J. D; Cramer, C. J (2002). "Electronic structure and bonding in hexacoordinate silyl-palladium complexes". Angewandte Chemie (International Ed. In English). 41 (11): 1953–6. doi:10.1002/1521-3773(20020603)41:11<1953::AID-ANIE1953>3.0.CO;2-H. PMID 19750644.
  23. ^ Yin, Xi; Warren, Steven A; Pan, Yung-Tin; Tsao, Kai-Chieh; Gray, Danielle L; Bertke, Jeffery; Yang, Hong (2014). "A Motif for Infinite Metal Atom Wires". Angewandte Chemie International Edition. 53 (51): 14087–14091. doi:10.1002/anie.201408461. PMID 25319757.
  24. ^ a b Usselman, Melvyn (1978). "The Wollaston/Chenevix controversy over the elemental nature of palladium: A curious episode in the history of chemistry". Annals of Science. 35 (6): 551–579. doi:10.1080/00033797800200431.
  25. ^ a b Griffith, W. P. (2003). "Rhodium and Palladium – Events Surrounding Its Discovery". Platinum Metals Review. 47 (4): 175–183.
  26. ^ Wollaston, W. H. (1804). "On a New Metal, Found in Crude Platina". Philosophical Transactions of the Royal Society of London. 94: 419–430. doi:10.1098/rstl.1804.0019.
  27. ^ Wollaston, W. H. (1805). "On the Discovery of Palladium; With Observations on Other Substances Found with Platina". Philosophical Transactions of the Royal Society of London. 95: 316–330. doi:10.1098/rstl.1805.0024.
  28. ^ Garrett, Christine E.; Prasad, Kapa (2004). "The Art of Meeting Palladium Specifications in Active Pharmaceutical Ingredients Produced by Pd-Catalyzed Reactions". Advanced Synthesis & Catalysis. 346 (8): 889–900. doi:10.1002/adsc.200404071.
  29. ^ a b c d Kielhorn, Janet; Melber, Christine; Keller, Detlef; Mangelsdorf, Inge (2002). "Palladium – A review of exposure and effects to human health". International Journal of Hygiene and Environmental Health. 205 (6): 417–32. doi:10.1078/1438-4639-00180. PMID 12455264.
  30. ^ Williamson, Alan. "Russian PGM Stocks" (PDF). The LBMA Precious Metals Conference 2003. The London Bullion Market Association. Retrieved 2 October 2010.
  31. ^ "Historical Palladium Prices and Price Chart". InvestmentMine. Retrieved 27 January 2015.
  32. ^ "Ford fears first loss in a decade". BBC News. 16 January 2002. Retrieved 19 September 2008.
  33. ^ a b "Platinum-Group Metals" (PDF). Mineral Commodity Summaries. United States Geological Survey. January 2007.
  34. ^ Nat Rudarakanchana (27 March 2014). "Palladium Fund Launches In South Africa, As Russian Supply Fears Warm Prices". International Business Times.
  35. ^ Rosenfeld, Everett (20 August 2014). "The other commodity that's leaping on Ukraine war". CNBC. Retrieved 29 January 2018.
  36. ^ "Palladium Rally Is About More Than Just Autos". Bloomberg.com. 30 August 2017. Retrieved 29 January 2018.
  37. ^ "Don't Expect Palladium Prices To Plunge | OilPrice.com". OilPrice.com. Retrieved 29 January 2018.
  38. ^ "USGS Minerals Information: Mineral Commodity Summaries". minerals.usgs.gov. Retrieved 29 January 2018.
  39. ^ ""Norilsk Nickel" Group announces preliminary consolidated production results for 4 th quarter and full 2016, and production outl". Nornickel. Retrieved 29 January 2018.
  40. ^ "Platinum-Group Metals" (PDF). Mineral Yearbook 2007. United States Geological Survey. January 2007.
  41. ^ Verryn, Sabine M. C.; Merkle, Roland K. W. (1994). "Compositional variation of cooperite, braggite, and vysotskite from the Bushveld Complex". Mineralogical Magazine. 58 (2): 223–234. Bibcode:1994MinM...58..223V. CiteSeerX 10.1.1.610.640. doi:10.1180/minmag.1994.058.391.05.
  42. ^ Genkin, A. D.; Evstigneeva, T. L. (1986). "Associations of platinum- group minerals of the Norilsk copper-nickel sulfide ores". Economic Geology. 8l (5): 1203–1212. doi:10.2113/gsecongeo.81.5.1203.
  43. ^ "Mindat.org - Mines, Minerals and More". www.mindat.org.
  44. ^ Kolarik, Zdenek; Renard, Edouard V. (2003). "Recovery of Value Fission Platinoids from Spent Nuclear Fuel. Part I PART I: General Considerations and Basic Chemistry" (PDF). Platinum Metals Review. 47 (2): 74–87.
  45. ^ a b c d "Palladium". United Nations Conference on Trade and Development. Archived from the original on 6 December 2006. Retrieved 5 February 2007.
  46. ^ Rushforth, Roy (2004). "Palladium in Restorative Dentistry: Superior Physical Properties make Palladium an Ideal Dental Metal". Platinum Metals Review. 48 (1).
  47. ^ Hesse, Rayner W. (2007). "palladium". Jewelry-making through history: an encyclopedia. Greenwood Publishing Group. p. 146. ISBN 978-0-313-33507-5.
  48. ^ Toff, Nancy (1996). The flute book: a complete guide for students and performers. Oxford University Press. p. 20. ISBN 978-0-19-510502-5.
  49. ^ Weithers, Timothy Martin (2006). "Precious Metals". Foreign exchange: a practical guide to the FX markets. p. 34. ISBN 978-0-471-73203-7.
  50. ^ Brown, William Henry; Foote, Christopher S; Iverson, Brent L (2009). "Catalytic reduction". Organic chemistry. Cengage Learning. p. 270. ISBN 978-0-495-38857-9.
  51. ^ Tsuji, Jiro (2004). Palladium reagents and catalysts: new perspectives for the 21st century. John Wiley and Sons. p. 90. ISBN 978-0-470-85032-9.
  52. ^ Drahl, Carmen (2008). "Palladium's Hidden Talent". Chemical & Engineering News. 86 (35): 53–56. doi:10.1021/cen-v086n035.p053.
  53. ^ Miller, Miles A; Askevold, Bjorn; Mikula, Hannes; Kohler, Rainer H; Pirovich, David; Weissleder, Ralph (2017). "Nano-palladium is a cellular catalyst for in vivo chemistry". Nature Communications. 8: 15906. Bibcode:2017NatCo...815906M. doi:10.1038/ncomms15906. PMC 5510178. PMID 28699627.
  54. ^ Zogbi, Dennis (3 February 2003). "Shifting Supply and Demand for Palladium in MLCCs". TTI, Inc.
  55. ^ Mroczkowski, Robert S. (1998). Electronic connector handbook: theory and applications. McGraw-Hill Professional. pp. 3–. ISBN 978-0-07-041401-3.
  56. ^ Harper, Charles A. (1997). Passive electronic component handbook. McGraw-Hill Professional. pp. 580–. ISBN 978-0-07-026698-8.
  57. ^ Jollie, David (2007). "Platinum 2007" (PDF). Johnson Matthey. Archived from the original (PDF) on 16 February 2008.
  58. ^ Shu, J.; Grandjean, B. P. A.; Neste, A. Van; Kaliaguine, S. (1991). "Catalytic palladium-based membrane reactors: A review". The Canadian Journal of Chemical Engineering. 69 (5): 1036. doi:10.1002/cjce.5450690503.
  59. ^ Allen, T. H.; Root, W. S. (1955). "An improved palladium chloride method for the determination of carbon monoxide in blood". The Journal of Biological Chemistry. 216 (1): 319–323. PMID 13252031.
  60. ^ Manchester, F. D.; San-Martin, A.; Pitre, J. M. (1994). "The H-Pd (hydrogen-palladium) System". Journal of Phase Equilibria. 15: 62–83. doi:10.1007/BF02667685.
  61. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1150–151. ISBN 978-0-08-037941-8.
  62. ^ Grochala, Wojciech; Edwards, Peter P. (2004). "Thermal Decomposition of the Non-Interstitial Hydrides for the Storage and Production of Hydrogen". Chemical Reviews. 104 (3): 1283–316. doi:10.1021/cr030691s. PMID 15008624.
  63. ^ Mott, N. F. and Jones, H. (1958) The Theory of Properties of metals and alloys. Oxford University Press. ISBN 0-486-60456-X. p. 200
  64. ^ Colon, Pierre; Pradelle-Plasse, Nelly; Galland, Jacques (2003). "Evaluation of the long-term corrosion behavior of dental amalgams: influence of palladium addition and particle morphology". Dental Materials. 19 (3): 232–9. doi:10.1016/S0109-5641(02)00035-0. PMID 12628436.
  65. ^ Gupta, Dinesh C.; Langer, Paul H.; ASTM Committee F-1 on Electronics (1987). Emerging semiconductor technology: a symposium. ASTM International. pp. 273–. ISBN 978-0-8031-0459-4.
  66. ^ Hindsen, M.; Spiren, A.; Bruze, M. (2005). "Cross-reactivity between nickel and palladium demonstrated by systemic administration of nickel". Contact Dermatitis. 53 (1): 2–8. doi:10.1111/j.0105-1873.2005.00577.x. PMID 15982224.
  67. ^ Holmes, E. (13 February 2007). "Palladium, Platinum's Cheaper Sister, Makes a Bid for Love". Wall Street Journal (Eastern edition). pp. B.1.
  68. ^ "Platinum-Group Metals" (PDF). Mineral Yearbook 2009. United States Geological Survey. January 2007.
  69. ^ "Platinum-Group Metals" (PDF). Mineral Yearbook 2006. United States Geological Survey. January 2007.
  70. ^ "Johnson Matthey Base Prices". 2019. Retrieved 7 January 2019.
  71. ^ Ware, Mike (2005). "Book Review of : Photography in Platinum and Palladium". Platinum Metals Review. 49 (4): 190–195. doi:10.1595/147106705X70291.
  72. ^ "Msds - 373192".
  73. ^ Hosseini et al, Metallomics, 2016,8, 252-259; DOI 10.1039/C5MT00249D
  74. ^ Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 384, 387. ISBN 978-0-19-960563-7.
  75. ^ Zereini, Fathi; Alt, Friedrich (2006). "Health Risk Potential of Palladium". Palladium emissions in the environment: analytical methods, environmental assessment and health effects. Springer Science & Business. pp. 549–563. ISBN 978-3-540-29219-7.
  76. ^ Wataha, J. C.; Hanks, C. T. (1996). "Biological effects of palladium and risk of using palladium in dental casting alloys". Journal of Oral Rehabilitation. 23 (5): 309–20. doi:10.1111/j.1365-2842.1996.tb00858.x. PMID 8736443.
  77. ^ Aberer, Werner; Holub, Henriette; Strohal, Robert; Slavicek, Rudolf (1993). "Palladium in dental alloys – the dermatologists' responsibility to warn?". Contact Dermatitis. 28 (3): 163–5. doi:10.1111/j.1600-0536.1993.tb03379.x. PMID 8462294.
  78. ^ Wataha, John C.; Shor, Kavita (2010). "Palladium alloys for biomedical devices". Expert Review of Medical Devices. 7 (4): 489–501. doi:10.1586/erd.10.25. PMID 20583886.

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