White Gold And Ammonia
Posted by admin on Thursday Jun 23, 2011 Under Gold tradingCLEANING PRECIOUS METALS
Caring for your gold jewelry
To maintain your jewelry’s sparkle, try to clean your jewelry on a regular basis – once a month is a good rule of thumb. A simple way to clean your gold or platinum jewelry is to soak it in warm water mixed with a few drops of ammonia. Gentle use of an old, soft-bristled (kid’s) toothbrush is useful for more extensive cleaning. After cleaning and rinsing, dry and polish with a soft cloth. Please always remember to close your drain if you are cleaning near a sink.
When you are not wearing your jewelry, store it in a fabric-lined case with separate compartments, or wrap pieces individually in soft tissue paper. Don’t take the risk of your jewelry pieces scratching one another.
While lasting and durable, gold can become scratched or dented, particularly if handled roughly. Regularly check your gold jewelry for loose prongs or any damage, promptly bringing it to a professional jeweler for repair if needed.
Cleaning White Gold Jewelry
One of the most frequently asked questions is how to clean white gold. When white gold is sold, it is always rhodium plated. Rhodium is a hard, durable, silvery-white metal that can be polished to a high shine. This gives white gold, which is actually a very pale yellow, a very white look in the showcase and on your finger. This white look will last varying amounts of time depending on wear and tear. On earrings it can last a lifetime. On rings the rhodium will start wearing off where there is a lot of friction. This usually starts by the shank (the part of the ring that goes around the finger) starting to “turn yellow”. This is the rhodium wearing off. As you continue to wear the ring, all the exposed edges and corners will start “yellowing” as well.
cleaning_before
The easiest and least expensive solution is to have your jewelry re-rhodiumed. You can usually do this at your local jeweler for a small fee or you can send your jewelry to us at DiamondIdeals and
cleaning_after
This is a temporary solution and will have to be repeated as this new layer wears off. A more permanent solution would be to consider having the experts at DiamondIdeals remount your stones in a platinum or palladium alloy ring.
The White Gold
So now we have ammonia. But what can we do with it? One option is to convert it to urea. Urea is an interesting substance. It is an organic chemical, which is also produced in the human body to dispose of nitrogen. It is also the chemical which proved wrong the common belief in the 18th century, that organic substances cannot be created from inorganic raw materials. In 1828, Friedrich Wöhler was the first to synthesize urea from inorganic compounds. At the end of the 19th century, a method was discovered to synthesize urea from ammonia and carbon dioxide. This process is still the basis for modern urea production.
Although urea is still used as fertilizer on a large scale, it is also a raw material for many other industries. Chemicals made from urea include urea formaldehyde, which is used to glue the wooden chips together in chipboard, and melamine, which is used as a finish on chipboard panels. Urea is also used in toothpaste and chewing gum (I bet you didn’t know that!) and some pharmaceuticals.
Technical stuff
Urea is synthesized from ammonia and carbon dioxide. Since carbon dioxide is a waste material from ammonia plants and carbon dioxide is expensive to transport, it is convenient to build ammonia and urea plants on the same location. The two raw materials react in a high pressure reactor. The reaction takes place in two stages in the same reactor. First, an intermediate is formed, called ammonium carbamate. If the mixture remains in the reactor long enough, the second reaction takes place: ammonium carbamate splits into water and urea. Since Murphy Law is always present, the ammonium carbamate is only partly converted, so at the top of the reactor we have a liquid containing urea, ammonium carbamate, water and ammonia. Ammonia? Yes! By adding more ammonia to the reactor then theoretically necessary, more ammonia carbamate is converted to urea (If you have some degree in chemical engineering you’ll understand. For all others: believe me, it’s true).
Urea and Ammonia last start up small
The next step is to separate the urea and water from the remaining ammonia and ammonium carbamate. There are several ways to accomplish this separation. Depending on age and make of a urea plant you will find different techniques. The one described below is somewhat older, but still accurate for a lot of urea plants.
After the liquid mixture leaves the reactor, we reduce the pressure. If we keep the temperature high enough during this “decompression”, the ammonium carbamate will fall apart in ammonia and carbon dioxide. Both ammonia and carbon dioxide are gaseous at this temperature and pressure, so these gasses will “evaporate” from the liquid mixture. This separation process is called decomposition (because the ammonium carbamate decomposes into ammonia and carbon dioxide) and is executed in vessels called decomposers. Usually the pressure is reduced in a few steps in different decomposers. After the last decomposer, all we have left is a mixture of urea and water or, since urea readily dissolves in water, a urea solution.
We’ll leave the urea solution for what it is and digress to the gases that leave the decomposers. Since it is a waste of raw materials (not to mention an environmental disaster!) to vent these gases into the atmosphere, they are recovered. In the decomposition section, we have seen that ammonium carbamate decomposes into ammonia and carbon dioxide, due to the low pressure and the high temperature. If we lower the temperature, the reverse reaction takes place: ammonia and carbon dioxide react back to ammonium carbamate. Simultaneously, the ammonium carbamate is absorbed into water. The resulting solution is recycled back to the reactor, where it will be (partly) converted to urea.
Urea by Night small
OK, back to the urea solution. We only want the urea, so we have to get the water out. Two methods are available: We can evaporate the water or we can crystallize the urea. Evaporation is the most common practice: the solution is heated and the water boils out of the solution. the final result is a urea melt, which still contains a little water (0.5 – 1 %). This method has one major drawback: impurities are not removed (worse: due to the heating process, extra impurities are created), and the end product only contains 98 to 99 % urea.
The other method is crystallization. In that case we do not heat the solution, but we create a vacuum above the solution. The vacuum “pulls” out the water, and the solution is concentrated until there is more urea then can be dissolved in the water: The urea starts to crystallize. If the “slurry” (the mixture of crystals and solution) contains enough crystals, it is sent to centrifuges, where the solution is separated from the crystals. The crystals are dried and the result is a very pure product. In crystalline form the urea purity can be higher then 99.8 %.
Now we come to the final step. Most customers prefer granules instead of a hot urea melt or crystals. Again several techniques are available to achieve this, but the most common process is (still) a process called “prilling”. This process takes place in a prill tower, which has some visual resemblance to a water tower (see picture). Before urea can be prilled it has to liquefied. The liquid urea is led to one or more “prillheads” in the top of the tower. These prillheads form droplets, which fall down a long, empty shaft. From the bottom of the tower, huge amounts of air are blown through the same shaft to cool the droplets so much that they will solidify while they are falling and reach the bottom of the tower as granules. These granules (with an average diameter of approximately 1.5 mm) are stored and are sold as bulk (transported in barges or silo trucks) or in bags of 25 to 1000 kg.
The popularity of white gold jewelry is now more uphill. For the moment of betrothal and marriage, many women choose white gold jewelry for its flexibility and its tendency to accentuate the color luster of diamonds.
prilltwr small
Basically, both white gold and yellow gold are both made of pure gold content of 75%. Because pure gold is too soft to be used as jewelry, so he combined with other metals. Yellow gold color is the result of a combination of gold with copper and zinc.
While white gold is a combination of gold with white metals such as zinc, nickel, or palladium. And in addition, also white gold plated silver thin metal called rhodium. Rhodium is a function to display the gold jewelry is a brilliant silvery white. Here are some tips to clean and care for white gold jewelry, jewelry for your pet beautiful and always well groomed.
White Gold Jewelry Cleaning Tips
* First, put your white gold jewelry in a soft towel. Place the towel away from the kitchen or bathroom sink, to prevent falls and doused jewelry.
* Combine 1 / 3 cup cold water with 1 / 3 cup of ammonia in the clean cup. Stir until well blended. Use ammonia mix to clean up a plain white gold jewelry. Do not use ammonia if you have white gold jewelry semi-precious stones, because ammonia is damaging the stone.
* Soak your white gold jewelry in the mixture of this water for about 15 minutes. Use a timer as a reminder alarm you to pick it back from the marinade.
* With a fluffy brush, brush each part of your white gold jewelry to remove droppings.
* Dry your white gold jewelry with a soft cotton cloth. Meanwhile, remove the mixture of liquid ammonia was clean and wash the cup holder.
* Once your white gold jewelry is completely dry, store neatly in your jewelry box.
Cleaning White-Gold Plain Wedding Rings
Years or even months of wear can turn white-gold a much duller version of itself. White-gold, mainly used for engagement and plain wedding rings, needs quite a bit of care as unlike gold and platinum it tarnishes and loses its shine much easier. Thus its vital that you keep white-gold as clean as possible. A regular clean will certainly bring that shine back to your cherished white-gold jewellery.
There are a number of steps you have to take if you want your white-gold ring to be fully clean and sparkling. First of all, clean the ring with a toothbrush, water and detergent free soap. Rub the ring with the toothbrush coated in water and soap until aptly polished and then wash the ring under clear running water. It’s vital that you clean the ring very gently indeed; otherwise you could end up with marks or scratches.
To get your ring to really shine and sparkle, soak the ring in ammonia for a short period of time. Mix together in a bowl, 1 part ammonia and I cup of warm water, then add the ring and leave for 15 minutes and no more – as leaving it too long could damage the plating. Only use this method if your white-gold ring is plain as it could damage the gemstones.
Make sure you dry the ring correctly; otherwise you may get undesirable temporary water stains on your ring. If left too long in moisture a white-gold ring will damage, as contact with too much moisture causes fractures in the plating. You could dry the ring with a soft piece of material or on the cool setting of a hairdryer. Never use heat on white-gold as this could have serious consequences for your ring.
White-gold needs a lot more maintenance than its counterparts. It needs to be stored separately from other jewellery, which may scratch its delicate plating. The plating is made of the element rhodium – which creates that lustrous shine – however it also wears away quite quickly. The rhodium plating will need to be replaced every one to two years, as it wears away and in turn causes the ring to look a dull brown. It’s also vital that you avoid when wearing this ring household chemicals as these can cause severe damage to the ring, especially if certain metal alloys are present.
THE SOURCES
