PONNIN KUDATTHINU POTTU VEANO? Whether tilak is required for Goldpot?
GOLD- PART 1 Dear friends, It was about 2 years back or so Icame across silver coloured gold jewellery in a shop in Chennai. Gold in silvercolour- It was new information to me. About a year back while exchanging someold jewellery I observed cleaning it on fire, the yellow colour of thejewellery becoming silver colour. The anxiety I kept with me inmind. Anything wrong?? The pawn brokers keep a liquidand just touch the jewellery with a small brush after dipping in the solution.If more copper or any amalgam, smokewould rise from the touched portion and would get extended to sides - If the jewellery is below 18 K gold it would react with the liquid. It is called acid test. I have seen this gold test done on myjewellery during pledging in the difficult days. Some not trust worthy jewellersjust dip the jewellery on some pretext in a liquid for some times. Later we would note about a gramof gold have been absorbed in the liquid and our ornament would weigh less.We maysuspect as innocent – due to wear and tear. Recently by surfing about theyellow metal I could gather there is green and blue colour goldjewellery also. Probably for members with moreChemistry knowledge this posting could be of least importance. I submissively admit I havestudied chemistry only up to Pre university level. I thought the information felt new to me canbe shared with friends along with otherinteresting information. I have kept minimum the toughscientific/chemistry matters. Sincerely, Gopala Krishnan 26-5-2013. Reposted on 2-2-2021 after editing and updating the compilation. R.Gopala Krishnan. 1. An introduction to Gold Gold has naming aurum in Latin, meaningglow of sunrise. In the periodic table (Listing of items in chemistry) it islisted under atomic number 79 with symbol Au. For a quick looking, it is listed betweenplatinum and mercury. Because Latin name is arum chemicalsymbol is Au. The relative density or specificgravity of gold is 19.3. This simply means Gold weighs more than 19 timesof the same volume of water. In simple language a papercontainer giving 250 cc coffee in trains would weigh 250 gms. But if gold dust is put in it to the same volume – 250x19.3 =4825 gm. Slightly lesser than ½ kg it would weigh. Whether one can lift it in paper cup?? The melting point is 1064 degree incentigrade. And boiling point is 2856 degree centigrade. Just as ice cube meltslowly keeping outside, goldtoo will start melt at about 1000 degree centigrade. This is tentimes the temperature in which the water boils. If a drop of melting gold fall on skin???. Still jewellery shops we sit near gold smith whilemelting. Most jewellery shops want the customer witness the melting now a days. Many shops donot melt to boiling point. But for making ornaments goldsmiths do not go to these highertemperatures. Gold is a very good conductor ofcurrent. It is a diamagnetic material. Diamagnetic means repelling to magneticfield. In simple wordsgold dust cannot be picked up with magnet. Gold is a dense, soft, shiny,malleable, and ductile metal. It has a bright yellow colour and lustretraditionally considered attractive, which it maintains withoutoxidizing in air or water. Chemically, gold is a transition metal and a group 11 element. It isone of the least reactive chemical elements, solid under standard conditions. The metal therefore occurs often infree elemental (native) form, as nuggets or grains in rocks, in veins and inalluvial deposits. Less commonly, it occurs in minerals as goldcompounds, usually with tellurium. Gold resists attacks byindividual acids, but it can be dissolved by the aqua regia (nitro-hydrochloric acid), sonamed because it dissolves gold. Gold also dissolves in alkalinesolutions of cyanide, which have been used in mining. It dissolvesin mercury, forming amalgam alloys; is insoluble in nitric acid, which dissolves silver andbase metals, a property that has long been used to confirm the presence of goldin items, giving rise to the term acid test. This metal has been a valuableand highly sought-after precious metal for coinage, jewellery, and other arts since long before thebeginning of recorded history. Discovery of Gold is estimatedbefore 6000 BC The world consumption of new goldproduced is about 50% in jewellery, 40% in investments, and 10% in industry. Some telecommunication relaycontacts used golden tips in EARLIER technologies. Besides its widespread monetaryand symbolic functions, gold has many practical uses indentistry, electronics, and other fields. Its high malleability,ductility, resistance to corrosion and most other chemical reactions, andconductivity of electricity has led to many uses, including electric wiring,collared-glass production, and gold leafing. My note- On those days we could see many with gold teeth.Covering a treated and rectified tooth with gold leaf. Now a day we see rarelypeople with good teeth. With root canal and ceramic cap easily one cannotdistinguish the artificial teeth/tooth from natural one. With ceramic cap the teeth/tooth appear beautiful and natural. 2. Where is Gold in the earth? Most of the Earth's gold lies atits core, the metal's high density having made it sink there in the planet'syouth. Virtually all discovered gold is considered to have been deposited later by meteorites that contained the element 3. Characteristics of Gold Gold is the most malleable of allmetals; a single gram can be beaten into a sheet of 1 squaremeter. Gold leaf can be beaten thin enoughto become transparent. The transmitted light appears greenishblue, because goldstrongly reflects yellow and red. Such semi-transparent sheets alsostrongly reflect infrared light, making them useful as infrared (radiant heat)shields in visors of heat-resistant suits, and in sun-visors for space suits. Gold readily creates alloys withmany other metals. These alloys can be produced to modify the hardness andother metallurgical properties, to control melting point or to create exotic colours. Gold is a good conductor of heatand electricity and reflects infrared radiation strongly. Chemically, it isunaffected by air, moisture and most corrosive reagents, and is therefore wellsuited for use in coins and jewellery and as a protective coating on other,more reactive metals. However, it is not chemically inert. Gold is almostinsoluble, but can be dissolved in aqua regia. Now I told about dissolving goldin acid- Gold ions in solution are readily reduced and precipitated as metal byadding any other metal as the reducing agent. The added metal is oxidized anddissolves, allowing the gold to be displaced from solution and be recovered asa solid precipitate. 3a. Comparison with lead In addition, gold is very dense, a cubic meter weighing 19,300 kg.By comparison, the specific gravity of lead is 11.34. This means a piece ofgold of the same size of a lead sheet, will weigh more than 1.5 times of the lead sheet-a more familiar and easily available metal to understand. 4. Colours of Gold We know about electrons, protonsand neutrons in the atom. The electrons are orbiting and the one on the outershell of the atom is called valance electrons. It is thedensity of these valance electrons gives the colour to the gold. Rose Gold- Common collared gold alloys such as rose gold canbe created by the addition of various amounts of copper and silver. Alloys containing palladium or nickel are alsoimportant in commercial jewellery as these produce white gold alloys. Less commonly, addition of manganese,aluminium, iron, indium and other elements can produce more unusual colours ofgold for various applications. Update- Seeing copper colourappearing in gold bangles on those days Gold was considered impure. I will continue in another posting. -- You received this message because you are subscribed to the Google Groups "Thatha_Patty" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/thatha_patty/2016159615.1343881.1612275170513%40mail.yahoo.com.
