Rhodium

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78 grams of rhodium

Rhodium is a silver-white metallic element that is highly reflective and resistant to corrosion. It is considered the rarest and most valuable precious metal in the world — well above gold or silver. The name rhodium comes from the Greek word “rhodon,” meaning rose, named for the rose-red color of its salts.

  • Atomic number (number of protons in the nucleus): 45
  • Atomic symbol (on the periodic table of the elements): Rh
  • Atomic weight (average mass of the atom): 102.90550
  • Density: 12.41 grams per cubic centimeter
  • Phase at room temperature: Solid
  • Melting point: 3,567 degrees F (1,964 degrees C)
  • Boiling point: 6,683 degrees F (3,695 degrees C)
  • Number of isotopes (atoms of the same element with a different number of neutrons):  24 whose half-lives are known; one stable
  • Most common isotopes: One stable isotope Rh-103

Rhodium is one of the of the six platinum group metals: platinum, palladium, rhodium, osmium, iridium and ruthenium. It is also classified as a noble metal, meaning that it does not react to oxygen easily, acts as a fantastic catalyst and is resistant to corrosion and oxidation. Some common characteristics of the platinum group metals include high melting points, general non-toxicity, and resistance to wear, oxidation and corrosion, according to Chemistry Libretexts.

Rhodium is the rarest of the platinum group, only occurring up to one part per 200 million in the Earth’s crust, according to Chemistry Libretexts. Rhodium has lower density and a higher melting point than platinum. Rhodium it is unaffected by air and water up to 1,112 degrees Fahrenheit (600 degrees Celsius), according to Lenntech.

Rhodium was discovered in 1803 by English chemist William Hyde Wollaston shortly after he had discovered the element palladium. Wollaston extracted rhodium from a piece of platinum ore that he had obtained from South America. Rhodium often occurs with deposits of platinum and is commonly obtained from the mining and refining of platinum.

Wollaston was first alerted to the possibility of a new element existing in platinum ore by the French chemist Hippolyte-Victor Collet-Descotils, who believed that the red color of some platinum salts was due to the presence of an unidentified metal. After a series of chemical reactions, Wollaston was able to remove the platinum and palladium from the sample of platinum ore. He was left with a dark red powder — which turned out to be sodium rhodium chloride, according to Jefferson Lab.

The main use for rhodium is in catalytic converters designed to clean vehicle emissions. Rhodium — often together with palladium and/or platinum — accomplishes this by reducing nitrogen oxide in exhaust gas. Without rhodium catalysts, the air in our cities would be much worse due to vehicle exhausts.

Since rhodium is quite brilliant and resistant to tarnishing, it is used as a finish for jewelry, searchlights and mirrors. It is also alloyed with platinum for aircraft turbine engines. In the chemical industry, rhodium is used as a catalyst in the making of nitric acid, acetic acid and hydrogenation reactions, according to the Royal Society of Chemistry (RSC).Other uses for rhodium are coating optic fibers, crucibles, thermocouple elements and headlight reflectors. Since it has a low electrical resistance and is highly resistant to corrosion, it is used as an electrical contact material as well, according to RSC.

Rhodium is often alloyed with platinum and iridium to make an oxidation-resistant metal that can stand against high temperatures. These alloys are used in furnace windings, pen nibs, phonograph needles, high-temperature thermocouple and resistance wires, electrodes for aircraft spark plugs, bearings and electrical contacts, according toLenntech.

Rhodium has no known biological use and no known use for life processes. While some compounds of rhodium are carcinogenic, there are almost no reported cases of humans being affected by this element in any way. This may be because rhodium compounds are encountered so rarely. Test on plants have shown that it is the least toxic member of the platinum group of metals, according to Lenntech.

Although rhodium is generally considered non-toxic, some of its compounds are toxic and carcinogenic. Naturally occurring rhodium consists of just one stable isotope: Rh-103.

  • An alloy of rhodium-platinum is used in heart pacemakers.
  • South African PGM producers extract a mix of metals comprising approximately 60 percent platinum, 30 percent palladium and 10 percent rhodium, according to Mining.com.
  • Rhodium is resistant to most acids.
  • Rhodium metal is rarely used by itself and almost always as an alloy.
  • Of the three precious metals (rhodium, platinum and palladium) currently used in vehicle catalytic converters, rhodium has by far the highest activity for the removal of nitrogen oxides (NOx) from the exhaust. It also has very high activity for the oxidation of hydrocarbons (HC) and carbon monoxide (CO) and very good resistance to the poisons present in the exhaust stream, according to Eastern Catalytic. Its primary drawback, however, is its high cost.
  • All rhodium compounds are easily reduced or decomposed through heating to create powdered (or sponge) metal.

Commercial rhodium is generally obtained as a byproduct of copper and nickel refining. In nature, rhodium can occur uncombined or with other platinum minerals. It can be found in river sands in North and South America and in copper-nickel sulfide ores in Ontario, Canada, according to the Royal Society of Chemistry.

Due to its rarity, the small market size and the concentrated supply — South Africa alone produces roughly 80 percent of the world’s rhodium — prices are typically volatile, according to Mining.com. For example, rhodium briefly reached $10,025 an ounce just before the 2008 financial crisis hit, but then plunged 90 percent before the end of the year. In 2017, the price of rhodium more than doubled, adding $1,000 an ounce since hitting 12-year-lows mid-2016.

History of Sterling Silver

History of Sterling Silver

Characteristics of Sterling Silver

The whitest of all of the precious metals, sterling silver has been heralded for centuries for its highly lustrous finish and versatile applications. Although harder than gold, sterling silver is still considered one of the more pliable and supple metals. Its malleability makes silver easy to hammer and mold into various forms and shapes. Silver melts at a slightly lower temperature than gold (1760 degrees F as opposed to 1960 degrees F).

 

 

Naming & History of Sterling Silver

Dating back to the time of primitive man, silver has been referred to by many different naming conventions. The story of how the word “sterling” was incorporated into the name is rooted in 12th-century lore. As payment for English cattle, an association of eastern Germans compensated the British with silver coins dubbed “Easterlings.” Eventually, the Easterling was widely accepted as a standard of English currency. The name was ultimately abbreviated to “Sterling,” which is now used to refer to the highest grade of silver metal.

 

The official designation of “sterling” to a piece of silver indicates that it contains at least 92.5% of pure silver. The remaining 7.5% can be comprised of any other metal alloy, most commonly copper. Although it may seem that an even higher silver content would be desirable, that’s not actually the case. Metal alloys with a silver content of more than 92.5% are too pliable to be used without suffering from dents and dings. The second alloy is required to ensure the metal’s stability and resilience.

 

Other Types of Silver
In addition to sterling silver, which contains 92.5% silver and 7.5% copper alloy, there are many different varieties and grades of silver in production throughout the world:

 

Fine silverThis type of silver has a silver content of 99.9% or higher. Fine silver is much too soft to be used in everyday applications, such as jewelry, d?r accents, or tableware. This premium class of silver is used to make bullion bars for international commerce.

 

Britannia silver: A higher grade than sterling silver, Britannia has a silver content of at least 95.84%. Originating as a standard in Britain as far back as 1697, Britannia silver is denoted by a hallmark stamp of “958” to indicate its silver content, sometimes accompanied by the symbol of Britannia.

 

Mexican silver: Another premium silver, Mexican silver consists of at least 95% pure silver and 5% copper. This elite form of the metal is not currently in wide circulation in Mexico; most of the silver jewelry and accents sold in Mexican marketplaces is forged from 92.5% sterling.

 

 Coin silver: Comprised of 90% silver and 10% copper, coin silver is made from melting down standard silver coins. Lower in silver content than sterling, this metal was widely used as silver tableware in the United States between 1820 and 1868, and as common currency until 1964.

 

 German silver: This term is usually used to refer to 800-standard silver, which consists of 80% silver and is commonly used for silverware, silver tableware, and decorative silver accents. 900-standard silver is another higher-grade version of German silver, and has a 90% silver content.

 

 

History of Sterling Silver in Fine Dining
If you’ve ever attended a very formal dinner party, you may have noticed the use of sterling silver tableware in some capacity. With its polished luster and timeless elegance, the addition of silver has the power to turn any ordinary meal into an elaborate event. Although used more sparingly today, the precious metal was historically a key component in setting a proper table.

 

The use of sterling silver in fine dining was most prevalent between 1840 and 1940, with the biggest surge between 1870 and 1920. During this time, the production and merchandising of silver ramped up considerably to accommodate the growing demand.

 

During the Victorian era, it was frowned upon to ever touch or handle food without the use of a utensil. The ultimate criterion for a fine dining table was sterling silver flatware, a must when setting a table for a formal meal in the United States and Europe. Silver flatware collections were extensive, often including up to 100 pieces. Formal dinners in the late 1800s and early 1900s were long, extravagant affairs, sometimes including up to 10 or more courses, each of which demanded its own set of silver utensils. It wasn’t uncommon to use several different types of sterling silver forks, spoons, and knives during a typical dinner.

 

Sterling silver was also used for serving pieces, such as large forks, cake knives, carving knives, soup spoons, and gravy ladles. In addition to its pleasing aesthetic properties, silver’s heft and stability made it a serviceable tool for cutting and serving food. Often, silver serving pieces were embellished with hand-carved designs and ivory accents.

 

And it didn’t stop there. Decorative table accents included sterling silver napkin rings, coasters, and elaborate silver candlesticks. After the meal, the precious metal was used for pots of hot water for tea, post-dinner liqueur goblets, sterling silver water pitchers, silver mint julep cups, and dishes of melted chocolate for topping desserts.

 

The prevalence of sterling silver in fine dining waned a bit in the mid-1900s, mainly due to rising costs of silver production. With modernity came a faster pace of life-people were busier and more rushed, and the elaborate, multi-course dinners that had once been the norm were relegated to only very special occasions among the upper class. Sterling silver dishes and tableware required a more time-consuming cleaning process than other materials, which also contributed to its diminishing popularity at the dinner table.

 

Today, although it’s not as widely used as it was during the Victorian era, there are many different ways you can revive the tradition of incorporating pure sterling silver tableware into a fine dining setting. Display hors d’oeuvres on a silver platter, or fill ornate silver cups with sugar and cream for coffee. Sterling silver flatware continues to make a grand impression, and serves as a luxurious wedding or housewarming gift. Accents such as silver candlesticks, vases, and sterling silver place card holders are also great ways to include the fine metal in your table decor.

 

https://www.silvergallery.com/history-of-sterling-silver/

Facts About Silver Jewelry And Gold Jewelry Metals/

Facts About Silver Jewelry And Gold Jewelry Metals/

What You Should Know – Silver and Gold Jewelry

About Silver Accessories and Karat Gold Jewelry

The two precious metals most often used in jewelry are alloys of silver and gold.

There are many different alloys used in modern jewelry making.

The type of jewelry you can wear is not just determined by your wallet –
but also by the way your body reacts to and tolerates exposure to metals.

Sterling silver tarnishes, especially in hot, humid weather. It contains 7.5% copper
by weight, which reacts with common air pollutants, darkening the surface of the metal.

This can prompt skin irritation if your skin is sensitive to (usually) nickel or Fats about (sometimes) copper.

If you have noticed that you have an itch that persists with drying and reddening of your
skin where your jewelry touches it, you are probably sensitive to the alloy in the metal.

Gold and silver are known to be non – reactive metals; but that does not mean
that everyone can wear any type of gold or silver jewelry without any problem.

Understanding more about metals can help you to choose
jewelry that is more comfortable and healthy for you to wear!

Higher karat gold alloys tend to be better tolerated than lower karat qualities because there is
less of the reactive metal in the alloy. Many people wear 18K or 22K gold jewelry for this reason.

Sterling silver is .925 pure, or 92.5% silver by weight, a very high percentage.
Most people don’t have any problems wearing sterling silver jewelry.

Modern silver alloys don’t contain nickel, the usual irritant in jewelry metals. Lower percentage
silver alloys like vintage “European” silver can irritate your skin more easily than sterling silver jewelry
if you have copper sensitive skin, because old European silver is .800 fine, or 80% silver / 20% copper.

Following is a listing of metals commonly used in jewelry making and an explanation of their properties.


Gold Facts – Alloys, Karats, and more!

Pure 24K gold is hypoallergenic. It doesn’t cause irritation to the body.

However, the metals mixed with gold to make it harder or
enhance the color of gold can cause adverse skin reactions.

Gold is very malleable, meaning it can be hammered
into very thin sheets – thin enough for light to pass through.

Gold is also very ductile – it can be pulled
through drawplates into wire much thinner than hair.

Pure gold is very soft. It is very easy to work with hand tools.To make it harder
it is mixed with other metals, creating an alloy. Gold alloy purity is expressed in karats.

Gold alloys are available in many colors. The color of the alloy is determined
by the percentage and type(s) of metal “mixed” with the pure gold.

Rose gold contains more copper; until recently
white gold was traditionally made with nickel.

Now white gold is also made with palladium, a platinum
family metal; green gold is made with an alloy of fine silver.
As an example, most green gold is 18 karat; 75% gold, 25% silver.

There are MANY other colors made with alloy combinations.

The percentage of gold used is directly related to the karat content of the alloy.

It does not matter what type of metal is “mixed” with the gold, just how much.

The chart (below) shows how much gold is in your jewelry.


1k Gold = 4.17% Gold and 95.83% alloy

2k Gold = 8.33% Gold and 91.67% alloy

3k Gold = 12.5% Gold and 87.5% alloy

4k Gold = 16.67% Gold and 83.33% alloy

5k Gold = 20.83% Gold and 79.17% alloy

6k Gold = 25% Gold and 75% alloy

7k Gold = 29.17% Gold and 70.83% alloy

8k Gold = 33.3% Gold and 66.67% alloy

9k Gold = 37.5% Gold and 62.5% alloy

10k Gold = 41.67% Gold and 58.33% alloy

11k Gold = 45.83% Gold and 54.17% alloy

12k Gold = 50% Gold and 50% alloy

13k Gold = 54.17% Gold and 45.83% alloy

14k Gold = 58.33% Gold and 41.67% alloy

15k Gold = 62.5% Gold and 37.5% alloy

16k Gold = 66.67% Gold and 33.33% alloy

17k Gold = 70.83% Gold and 29.17% alloy

18k Gold = 75% Gold and 25% alloy

19k Gold = 79.1% Gold and 20.83% alloy

20k Gold = 83.33% Gold and 16.67% alloy

21k Gold = 87.5% Gold and 12.5% alloy

22k Gold = 91.67% Gold and 8.33% alloy

23k Gold = 95.83% Gold and 4.17% alloy

24k Gold = 100% Gold and 0% alloy


In this chart, “alloy” means the other metal. It can be
silver, copper, zinc, nickel, iron or almost any other metal.

For instance, 10 karat yellow gold is 41.67% pure gold and 58.33% “other metals”,
mostly copper, maybe some silver and most likely some nickel or zinc to add hardness.

In the United States gold must be at least 9K to be sold as karat gold.

Lower karat gold alloys have a  higher percentage of the other metals added to them.

They tend to react to the pollutants and other
impurities in the air faster than higher karat gold alloys.

This means that the high percentage of copper or other metal in the
lower karat alloy will tarnish (or oxidize), just like sterling silver items do.

This can occur especially in hot weather when the metals react to salt in perspiration.

If this happens to your sterling silver or lower karat gold jewelry, you may want to take it off
and wash the piece in hot water with a detergent like Dawn, Joy or whatever you prefer.

If your jewelry is really dirty, try scrubbing it carefully with a soft toothbrush.
Polish with a jewelry polishing cloth, if you have one. Rinse and dry before wearing.

If you have a problem with sterling silver, medium to
low karat gold will probably give you difficulties as well.

Medium to low karat yellow gold has a much higher percentage of copper in it than sterling silver.

Nickel allergies are the most common. Many people have problems wearing white gold –
the problem isn’t the gold. It’s actually nickel – the alloy – that causes skin reactions!

The new palladium white gold alloys are a bit more expensive, but are hypoallergenic.


Silver Jewelry Metal Facts

Sterling silver is generally used for jewelry, and that is what most people think of when they see silver.

Silver also comes in various quality grades, measured by 1/1000 parts per gram.

There are impurities that naturally occur in silver at the molecular level. These impurities
consist of other metals – usually copper, but traces of other metals can also be found.

These trace impurities are insignificant, and would be
too costly to remove – so .999 silver is considered pure.

The table (below) shows the types of silver alloys generally used in jewelry making.

Silver Alloys

.999 
fine silver

Contains .001 trace metals.

.9584
Britannia

95.84% silver + 4.16% copper.

.925
sterling

92.5% silver + 7.5% copper.

.900
coin

90% silver + 10% copper.

.830
European

83% silver + 17% copper.

.800
European

80% silver + 20% copper.

All the alloys shown are legally referred to as “silver”.

The only legal requirement is that they are quality stamped or marked for sale to the public.

Silver Facts

As with gold, silver in its fine state is a non – reactive metal – allergies are possible but VERY rare.

People who have problems wearing silver jewelry are usually
allergic to the copper in the alloyed metal, not the silver.

During the European Industrial Revolution, people found that their .800 silver was tarnishing
much faster than before – a reaction to the new pollutants in the air – from burning coal in the factories!

Fine, or pure, silver with no copper content does not tarnish easily. Think about the fine silver
coins brought up from wrecked ships – everything from the Atocha to sunken pirate ships.

They come up out of the ocean after hundreds of years bright and shiny as new.

Fine silver can get dirty, of course, but will not tarnish like sterling silver.

There is a new alloy called Argentium® Silver. It is sterling, but contains germanium in place of copper.

Argentium® doesn’t develop firescale as easily during soldering and doesn’t tarnish the way
traditional sterling silver does because the germanium doesn’t react as the copper does.


Plated and Filled

There are different grades and methods of bonding precious metals to
a less expensive base metal, as indicated in the chart below.

Finished, Washed, Colored

These terms refer to the thinnest gold, silver, platinum or rhodium coatings. 
There is no standard thickness.

Plated, Electroplated

These metals have a required minimum standard thickness – usually .15 – .25 mils

Gold, Platinum or Silver Filled metals

A layer of karat gold, platinum or silver is mechanically
bonded to a base metal, usually brass or steel.

Filled metals usually have a thickness over 100 times that of plated metals.

Gold filled may be  marked with the gold percentage by weight and the karat value.

If a piece of jewelry is marked 1/20 14K GF – 5% of the total weight is 14K gold.
However, this is not required by law. Most times the quality is stated on a hang tag.

There is no approved marking system in the US for filled metals.

 Vermeil Gold plated over silver

Silver is the “base” metal

Many jewelry items are made of either plated or filled metals.

This is done to keep the cost of these items as low as possible.

The whole piece can be plated or filled metal, as with a chain. In many cases, the clasp and
metal parts of an otherwise top quality gemstone bead necklace or bracelet can be plated or filled.

If it is taken care of and worn properly, such as over a sweater, a necklace with plated parts
can last for a very reasonable length of time, even years – but eventually the plated
metal parts will oxidize or the plating will wear through to the base metal.

Filled metals are much higher quality and a much longer useful lifespan.

They have one or more layers of precious metal bonded to a base with heat and pressure.

Filled materials are at least 1/20 precious metal by weight.

They are much longer lasting than ordinary plated objects.

Filled metal objects are not usually marked with a quality stamp, such as 12k GF or 14k GF.

For information on the care and cleaning of jewelry, please visit this article:Jewelry Care

Article written by Robert Edwards ©2015.
Robert is a jeweler and metalsmith, and is webmaster of http://www.jewelry24seven.com.

This article may be linked and used as content on blogs and websites conditionally … ALL content –
links, author, copyright – must not be changed in ANY way – it must appear exactly as the article appears above.

 

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