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Metal Detection in coins
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Aim
To determine different metals present in different coins.
Requirements
Apparatus
1.Test Tubes 2.Beakers3.Funnel4.Filter Paper5.Burner6.China Dish7.Wire Gauze8.Tripod Stand 9.Test Tube Holder
Chemicals Required
1.Concentrated Nitric Acid2.Concentrated Hydrochloric Acid3.Dilute Hydrochloric Acid4.Hydrogen Sulphide5.Ammonium Hydroxide6.Ammonium Chloride7.Potassium Ferrocyanide8.Potassium Sulphocyanide9.DMG (Dimethyl Glyoxime)
Procedure
1.Prepare 100mL aqua regia by mixing 25mL concentrated nitric acid and 75mL concentrated hydrochloric acid.
2.Take 5mL of aqua regia in a china dish.3.Place the coin to be tested inside the china dish
carefully.4.Heat the china dish along with its contents.5.Wait for the metal in the coin to corrode in the
aqua regia.6.Take out the coin from the china dish and pour
the liquid left in the dish in a beaker.7.Use this liquid to test for the metals present in
the coin.8.Repeat the same procedure for different coins.
Observation Table
One Rupee Coin
Experiment Observation InferenceGroup ITo the original solution dil. HCl was added
No ppt. was formed Group I is absent
Group IITo the original solution dil. HCl was added and H2S gas was passed
No ppt. was formed Group II is absent
Group IIITo the original solution NH4Cland NH4OH were added
Confirmation:-The ppt. was filtered and HCl was added and then divided into parts.
1. K4[Fe(CN)6] was added to first part.
2. KSCN was added to second part.
Reddish brown ppt. was formed
Blue ppt. was formed
Blood red ppt. was formed
Fe3+ ions may be present
Fe3+ ions confirmed
Group IVTo the original solution NH4Cland NH4OH were added and H2S gas was passed
Confirmation:-The ppt. was dissolved in aqua regia and few drops of DMG and excess of NH4OH were added
Black ppt. was formed
Scarlet red ppt. was formed
Ni2+ ions may be present
Ni2+ ions confirmed
Two Rupee Coin
Experiment Observation InferenceGroup I
To the original solution dil. HCl was added
No ppt. was formed Group I is absent
Group IITo the original solution dil. HCl was added and H2S gas was passed
No ppt. was formed Group II is absent
Group IIITo the original solution NH4Cland NH4OH were added
Confirmation:-The ppt. was filtered and HCl was added and then divided into parts.
1. K4[Fe(CN)6] was added to first part.
2. KSCN was added to second part.
Reddish brown ppt. was formed
Blue ppt. was formed
Blood red ppt. was formed
Fe3+ ions may be present
Fe3+ ions confirmed
Group IVTo the original solution NH4Cland NH4OH were added and H2S gas was passed
Confirmation:-The ppt. was dissolved in aqua regia and few drops of DMG and excess of NH4OH were added
Black ppt. was formed
Scarlet red ppt. was formed
Ni2+ ions may be present
Ni2+ ions confirmed
Five Rupee Coin
Experiment Observation InferenceGroup I
To the original solution dil. HCl was added
No ppt. was formed Group I is absent
Group IITo the original solution dil. HCl was added and H2S gas was passed
Confirmation:-Ppt. was filtered and divided into two parts.
1. K4[Fe(CN)6] was added to first part.
2. KSCN was added to second part.
Black ppt. was formed
Chocolate brown colour appearedDeep blue colour appeared
Cu2+ ions may be present
Cu2+ ions confirmed
Group IIITo the original solution NH4Cland NH4OH were added
Confirmation:-The ppt. was filtered and HCl was added and then divided into parts.
1. K4[Fe(CN)6] was added to first part.
2. KSCN was added to second part.
Reddish brown ppt. was formed
Blue ppt. was formed
Blood red ppt. was formed
Fe3+ ions may be present
Fe3+ ions confirmed
Group IVTo the original solution NH4Cland NH4OH were added and H2S gas was passed
Confirmation:-The ppt. was dissolved in aqua regia and few drops of DMG and excess of NH4OH were added
Black ppt. was formed
Scarlet red ppt. was formed
Ni2+ ions may be present
Ni2+ ions confirmed
Result
1.One Rupee coin contains iron and nickel metals.2.Two Rupee coin contains iron and nickel metals.3.Five Rupee coin contains iron, nickel and copper
metals.
Precautions
1.All acids and aqua regia should be handled with care.
2.Chemicals should not be misused.3.Burner should be used carefully.4.Vapours rising from the heated solutions must
not be inhaled.
Chemical Reactions Involved
Cu2+ + 4NH4OH [Cu(NH3)4]2+ + 4H2O
Deep blue complex
2Cu2+ + K4[Fe(CN)6] Cu2[Fe(CN)6] + 4K+
Chocolate brown ppt.
4Fe3+ + 3K4[Fe(CN)6] Fe4[Fe(CN)6]3 + 12K+
Dark blue ppt.
Fe3+ + 3KSCN Fe(SCN)3 + 3K+
Blood red ppt.
DMG Scarlet red ppt.
Theory
MetalA metal (from Greek "μέταλλον" – métallon, "mine, quarry, metal") is a solid material (an element, compound, or alloy) that is typically hard, opaque, shiny, and features good electrical and thermal conductivity. Metals are generally malleable—that is, they can be hammered or pressed permanently out of shape without breaking or cracking—as well as fusible (able to be fused or melted) and ductile (able to be drawn out into a thin wire). 91 of the 118 elements in the periodic table are metals.
AlloyAn alloy is a mixture or solid solution composed of a metal and another element. An alloy will contain one or more of the three: a solid solution of the elements (a single phase); a mixture of metallic phases (two or more solutions); an intermetallic compound with no distinct boundary between the phases. Solid solution alloys give a single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on the thermal (heat treatment) history of the material. An intermetallic compound will have another alloy or pure metal embedded within another pure metal.
Alloys are used in some applications as their properties are superior to those of the pure component elements for those applications. Examples of alloys are solder, brass, pewter, phosphor bronze and amalgam.
Aqua RegiaAqua regia (Latin and Ancient Italian, lit. "regal water"), aqua regis (Latin, lit. "king's water"), or nitro-hydrochloric acid is a highly corrosive mixture ofacids, a fuming yellow or red solution. The mixture is formed by freshly mixing concentrated nitric acid and hydrochloric acid, optimally in a volume ratio of 1:3. It was named so because it can dissolve the so-called royal or noble metals, gold and platinum. However, titanium, iridium, ruthenium,tantalum, osmium, rhodium and a few other metals are capable of withstanding its corrosive properties.
Aqua regia is primarily used to produce chloroauric acid, the electrolyte in the Wohlwill process. This process is used for refining highest quality (99.999%) gold.
Aqua regia is also used in etching and in specific analytic procedures. It is also used in some laboratories to clean glassware of organic compoundsand metal particles. This method is preferred over the "traditional" chromic acid bath for cleaning NMR tubes, because no traces of paramagneticchromium can remain to spoil spectra.[3] While chromic acid baths are discouraged because of the high toxicity of chromium and the potential for explosions, aqua regia is itself very corrosive and has been implicated in several explosions due to mishandling.[4]
Due to the reaction between its components resulting in its decomposition, aqua regia quickly loses its effectiveness (yet remains a strong acid), so its components are usually only mixed immediately before use.
Acknowledgement
I gratefully acknowledge the valuable contributions of Ms. Madhu Mehta and Mr. Rajesh without whom this project would not have been materialized.
Bibliography
http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Aqua_regia
Certificate
This is to certify that this project has been completed under my guidance and supervision by Tushar Garg, Class XII-A of Kulachi Hansraj Model School, Phase-III, Ashok Vihar, New Delhi, 110052.
Ms. Madhu Mehta
(Chemistry Dept.)