CHEM-GUIDE

Namaste & Welcome !!

2013-01-06T10:30:00.002-08:00

Chem-guide is a free resource for chemistry learning at school level (for 11 and 12). The resources in the blog has been compiled as per the syllabus of grade 11 and 12 prescribed by Higher Secondary Education Board, Nepal.

I hope chem-guide be a good tool for your chemistry learning. The links on your left is arranged into two categories. The resources presented in the link with (i) and (ii) refers the grade 11 and 12 chemistry resources respectively. For the detailed syllabus, click the respective links, Grade 11 and Grade 12.

I would be pleased to hear any comments from you about chem-guide on shrsth13@gmail.com

Thank you !!

Enjoy Surfing !!

BINOD SHRESTHA

Uses of halogens

2012-10-19T10:50:00.000-07:00

Bromine Uses:
Bromine was discovered in 1826 by French and German scientist named Antoine J. Balard and Carl J. Lowig respectively. Bromine is a reddish colored liquid which has a strong odor. It is in liquid form at room temperature and it gives off vapor freely. Bromine has an affinity to hydrogen, which makes it a good decomposer. Bromine is also used to disinfect water as it can kill the bacteria present in the water. The inorganic form of bromine is used in photography film, bromine is also used in fumigants, flame proofing agents, dyes and medicines.
Astatine Uses:
The word astatine is derived from the Greek word 'astatos' which means unstable. Astatine was discovered by University of California in 1940. It is solid at room temperature. One of the special characteristics of astatine is that it is not found in nature at all! It is produced by bombarding bismuth with alpha particles. The uses of astatine are not yet discovered.
Fluorine Uses:
Fluorine was discovered by Karl Scheele in 1771 and the word fluorine was derived from the word flow. It is in gaseous form at room temperature, which is said to be highly poisonous. There are many uses of fluorine such as making refrigerants, detergents etc. Fluorine is used mainly for producing uranium form hexafluroide and it is also used for making other fluorine compounds.

Earlier, fluorine was used to produce CFC's and these CFC's were used in aerosol sprays, cleaning agents and polymers. However it was found that these compounds can cause ozone layer depletion and so were banned. Other fluorine uses are as: it is used in rocket fuels as it is combustible. The most common of fluoride is in toothpaste. They are used in toothpaste because they are said to avoid dental cavities. In some countries, fluorine is added to municipal water supplies to reduce teeth decay. Fluorinated compounds can be used to create plastic and also for glass etching. Fluorinated compounds are not only used for decorative etching but also for marking glass bulbs as they are too thin to be etched.
Chlorine Uses:
Chlorine was first found by a Swedish chemist named Wilhelm Scheele in 1774. Chlorine is found in gaseous form at room temperature, it has a pungent and irritating odor and is yellowish green in color. The most important use of chlorine is as a bleach for manufacturing paper and cloth. Chlorine is one of the most commonly manufactured chemicals in the United States. The most common use of chlorine is in drinking water and swimming pool as it can kill harmful bacteria. Further uses of chlorine include production of everyday products such insecticides, solvents, food paints, plastic, dyes, textiles, petroleum products, paper products etc.
Iodine Uses:
Iodine is a very important element and has a lot of uses. The compounds are basically used in medicine, photography and dyes. Iodine forms starch which is an intense blue complex compound. Another very important use of iodine is as it is quite radioopaque, it can be used as X-ray radio contrast agent, for intravenous injection. Besides this iodine forms many compounds like potassium iodide which is of commercial use, and as sodium iodide which is useful in Finklestein reaction.

Preparation and uses of i. Silver chloride ii. Silver nitrate

2010-04-09T23:57:00.001-07:00

Silver Chloride

AgNO₃ combines with chloride ions and forms AgCl precipitate.

Properties

1) AgCl is obtained as a white precipitate

2) AgCl is insoluble in water.

3) It is soluble in aqueous ammonia

Silver Nitrate

In the preparation of silver nitrate dilute nitric acid is used. Silver combines with HNO₃ and forms silver nitrate.

Properties

It is colorless and is soluble in water.

On heating AgNO₃ decomposes and forms silver, nitrogen dioxide and oxygen.

AgNO₃ forms precipitates with chlorides, bromides, phosphates and sulphides. It is extensively used in laboratories.

Extraction of Silver by cyanide process and its uses

2010-04-09T23:54:00.000-07:00

Silver also occurs both in combined state as well as in free state. The important ores of silver are: Argentite (Ag₂S), Copper silver glance, Horn silver, Ruby silver. The silver ores are found along with gold ores in some parts of India.

Extraction

Silver is extracted from the ore-argentite (Ag₂S). The process of extraction of silver is called as cyanide process as sodium cyanide solution is used. The ore is crushed, concentrated and then treated with sodium cyanide solution. This reaction forms sodium argento cyanide.

The solution of sodium argento cyanide combines with zinc dust and forms sodium tetra cyanozicate and precipitated silver. This precipitated silver is called spongy silver.

The spongy silver is fused with potassium nitrate to obtain pure silver. Then the silver obtained is purified by electrolytic process.

Structure and uses of green vitriol, Ferric chloride, Mohr's salt

2010-04-09T23:53:00.002-07:00

Green Vitriol

Iron(II) sulfate (Iron(II) sulphate) or ferrous sulfate (ferrous sulphate) is the chemical compound with the formula (Fe S O₄), known since ancient times as copperas. It is most commonly encountered as the blue-green heptahydrate.

Hydrates

Iron(II) sulfate can be found in various states of hydration, and several of these forms exist in nature.

FeSO₄·H₂O (mineral: szomolnokite, relatively rare)
FeSO₄·4H₂O (mineral: rozenite, white, relatively common, may be dehydratation product of melanterite)
FeSO₄·5H₂O (mineral: siderotil, relatively rare)
FeSO₄·6H₂O (mineral: ferrohexahydrite, relatively rare)
FeSO₄·7H₂O (mineral: melanterite, blue-green, relatively common)

At 90 °C, the heptahydrate, also called green vitriol or copperas, loses water to form the colorless monohydrate, In its anhydrous, crystalline state, its standard enthalpy of formation is Δ_fH°_solid = -928.4 kJ·mol^-1 and its standard molar entropy is S°_solid = 107.5 J·K^-1·mol^-1. All mentioned mineral forms are connected with oxidation zones of Fe-bearing ore beds (pyrite, marcasite, chalcopyrite etc.) and related environments (like coal fire sites). Many undergo rapid dehydration and sometimes oxidation.

Uses

Industrially, ferrous sulfate is mainly used as a precursor to other iron compounds. It is a reducing agent, mostly for the reduction of chromate in cement.

Nutritional supplement

Together with other iron compounds, ferrous sulfate is used to fortify foods and to treat iron-deficiency anemia. Constipation is a frequent and uncomfortable side effect associated with the administration of oral iron supplements. Stool softeners often are prescribed to prevent constipation.

Colorant

Ferrous sulfate was used in the manufacture of inks, most notably iron gall ink, which was used from themiddle ages until the end of the eighteenth century. It also finds use in wool dyeing as a mordant.

Two different methods for the direct application of indigo dye were developed in England in the eighteenth century and remained in use well into the nineteenth century. One of these, known as china blue, involved iron(II) sulfate. After printing an insoluble form of indigo onto the fabric, the indigo was reduced toleuco-indigo in a sequence of baths of ferrous sulfate (with reoxidation to indigo in air between immersions). The china blue process could make sharp designs, but it could not produce the dark hues of other methods.

Ferrous sulfate can also be used to stain concrete and some limestones and sandstones a yellowish rust color.^[2]

Woodworkers use ferrous sulfate solutions to color maple wood a silvery hue.

Ferric Chloride

Iron(III) chloride, also called ferric chloride, is an industrial scale commodity chemical compound, with the formula Fe Cl₃. The colour of iron(III) chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red. Anhydrous iron(III) chloride isdeliquescent, forming hydrated hydrogen chloridemists in moist air. It is rarely observed in its natural form, mineral molysite, known mainly from some fumaroles.

When dissolved in water, iron(III) chloride undergoes hydrolysis and gives off heat in anexothermic reaction. The resulting brown, acidic, and corrosive solution is used as a coagulant insewage treatment and drinking water production, and as an etchant for copper-based metals inprinted circuit boards. Anhydrous iron(III) chloride is a fairly strong Lewis acid, and it is used as a catalyst in organic synthesis.

Reactions

Iron(III) chloride is a moderately strong Lewis acid, forming adducts with Lewis bases such astriphenylphosphine oxide, e.g. FeCl₃(OPPh₃)₂where Ph = phenyl.

Iron(III) chloride reacts with other chloride salts to give the yellow tetrahedral FeCl₄⁻ ion. Salts of FeCl₄⁻ in hydrochloric acid can be extracted intodiethyl ether.

When heated with iron(III) oxide at 350 °C, iron(III) chloride gives iron oxychloride, a layered solid and intercalation host.^{[citation needed]}

FeCl₃ + Fe₂O₃ → 3 FeOCl

In the presence of base, alkali metal alkoxidesreact to give the dimeric complexes:

2 FeCl₃ + 6 C₂H₅OH + 6 NH₃ → (Fe(OC₂H₅)₃)₂ + 6 NH₄Cl

Oxalates react rapidly with aqueous iron(III) chloride to give [Fe(C₂O₄)₃]³⁻. Other carboxylatesalts form complexes, e.g. citrate and tartrate.

Iron(III) chloride is a mild oxidising agent, for example capable of oxidising copper(I) chloride tocopper(II) chloride.

FeCl₃ + CuCl → FeCl₂ + CuCl₂

It also reacts with iron to form iron II chloride:

2 FeCl₃ + Fe → 3 FeCl₂

Reducing agents such as hydrazine convert iron(III) chloride to complexes of iron(II).

Laboratory use

In the laboratory iron(III) chloride is commonly employed as a Lewis acid for catalysing reactions such aschlorination of aromatic compounds and Friedel-Crafts reaction of aromatics. It is less powerful thanaluminium chloride, but in some cases this mildness leads to higher yields, for example in the alkylation of benzene:

The ferric chloride test is a traditional colorimetric test for phenols, which uses a 1% iron(III) chloride solution that has been neutralised with sodium hydroxide until a slight precipitate of FeO(OH) is formed.^[9] The mixture is filtered before use. The organic substance is dissolved in water, methanol orethanol, then the neutralised iron(III) chloride solution is added—a transient or permanent coloration (usually purple, green or blue) indicates the presence of a phenol or enol.

Mohr's Salt

Ammonium iron(II) sulfate, or Mohr's Salt, is a double salt of iron sulfate and ammonium sulfate, with the formula [NH₄]₂[Fe][SO₄]₂·6H₂O. Mohr's salt is preferred over iron(II) sulfate for titration purposes as it is much less affected byoxygen in the air than iron(II) sulfate, solutions of which tend to oxidise to iron(III). The oxidation of solutions of iron(II) is very pH dependent, occurring much more readily at high pH. The ammonium ions make solutions of Mohr's salt slightly acidic, which prevents this oxidation from occurring. The relevant equation for this is:
4 Fe²⁺ + O₂ + (4+2x) H₂O ⇌ 2 Fe₂O₃.xH₂O + 8 H⁺
The presence of protons keeps this equilibrium to the left, the Fe(II) side.
Mohr's salt is named after the German chemist Karl Friedrich Mohr, who made many important advances in the methodology of titration in the 19th century.

Uses and biological importance of iron

2010-04-09T23:53:00.001-07:00

Iron is essential to nearly all known organisms. In cells, iron is generally stored in the center of metalloproteins, because "free" iron (which binds non-specifically to many cellular components) can catalyze production of toxic free radicals.Iron deficiency can lead to iron deficiency anemia.

In animals, plants, and fungi, iron is often the metal ion incorporated into the heme complex. Heme is an essential component of cytochrome proteins, which mediate redoxreactions, and of oxygen carrier proteins such as hemoglobin,myoglobin, and leghemoglobin. Inorganic iron also contributes to redox reactions in the iron-sulfur clusters of manyenzymes, such as nitrogenase (involved in the synthesis ofammonia from nitrogen and hydrogen) and hydrogenase. Non-heme iron proteins include the enzymes methane monooxygenase (oxidizes methane to methanol), ribonucleotide reductase (reduces ribose todeoxyribose; DNA biosynthesis), hemerythrins (oxygen transport and fixation in Marine invertebrates) and purple acid phosphatase (hydrolysis of phosphate esters).

Iron distribution is heavily regulated in mammals, partly because iron has a high potential for biological toxicity. Iron distribution is also regulated because many bacteria require iron, so restricting its availability to bacteria (generally by sequestering it inside cells) can help to prevent or limit infections. This is probably the reason for the relatively low amounts of iron in mammalian milk. A major component of this regulation is the protein transferrin, which binds iron absorbed from the duodenum and carries it in the blood to cells

Rusting of iron and its prevention

2010-04-09T23:52:00.000-07:00

Rusting of Iron

The economic importance of rusting is such that it has been estimated that the cost of corrosion is over 1% of the world's economy. (25% of the annual steel production in the USA goes towards replacement of material that has corroded.)
Rusting of iron consists of the formation of hydrated oxide, Fe(OH)₃ or FeO(OH), and is an electrochemical process which requires the presence of water, oxygen and an electrolyte - in the absence of any one of these rusting does not occur to any significant extent. In air, a relative humidity of over 50% provides the necessary amount of water and at 80% corrosion is severe.

The process is complex and will depend in detail on the prevailing conditions, for example, in the presence of a small amount of O₂
the anodic oxidation will be: Fe → Fe²⁺ + 2e^-
and the cathodic reduction: 2H₂O + 2e^- → H₂ + 2OH^-
i.e. overall: Fe + 2H₂O → H₂ + Fe²⁺ + 2OH^-
i.e Fe(OH)₂ and this precipitates to form a coating that slows further corrosion.

If both water and air are present, then the corrosion can be severe with oxygen now as the oxidant
the anodic oxidations: 2Fe → 2Fe²⁺ + 4e^-
and the cathodic reduction: O₂ + 2H₂O + 4e^- → 4OH^-
i.e. overall: 2Fe + O₂ + 2H₂O → 2Fe(OH)₂ with limited O₂, magnetite is formed (Fe₃O₄), otherwise the familiar red-brown
Fe₂O₃ H₂O “rust” is found.

The presence of an electrolyte is required to provide a pathway for the current and, in urban areas, this is commonly iron(II) sulfate formed as a result of attack by atmospheric SO₂ but, in seaside areas, airborne particles of salt are important.
The anodic oxidation of the iron is usually localized in surface pits and crevices which allow the formation of adherent rust over the remaining surface area.

Rust prevention

Galvanised iron is the name given to iron that has been dipped into molten zinc (at about 450°C) to form a thin covering of zinc oxide. One level of rust prevention occurs through a purely mechanical method since it is more difficult for water and oxygen to reach the iron. Even if the layer becomes somewhat worn though another reason corrosion is inhibited is that the anodic processes are affected.
The E° for zinc oxidation (0.76V) is considerably more positive that E° for iron oxidation (0.44V) so the zinc metal is oxidized before the iron. Zn²⁺ is lost to the solution and the zinc coating is called a sacrificial anode.

Foodstuffs are often distributed in "tin cans" and it has generally been easier to coat the iron with a layer of tin than with zinc. Another benefit is that tin is less reactive then zinc so does not react as readily with the contents. However the electrode oxidation potential for Sn/Sn²⁺ is 0.14V so once again iron becomes the anode and rust will occur once the coating is worn or punctured.

Another technique is to treat the iron surface with dichromate solution.

2 Fe + 2 Na₂CrO₄ + 2 H₂O -> Fe₂O₃ + Cr₂O₃ + 4 NaOH

The iron oxide coating formed has been found to be impervious to water and oxygen so no further corrosion can occur.

Stainless steel

2010-04-09T23:51:00.000-07:00

Stainless Steel is a common name for metal alloys that consist of 10.5% or more Chromium (Cr) and more than 50% Iron (Fe). Although it is called "stainless", a better term for it is "highly stain resistant". A somewhat dark metal, it looks bright because it reflects light.

What are the main benefits of stainless steel in kitchen utensils?

♦ It is one of the most hygienic surfaces for the preparation of foods and very easy to clean, as its unique surface has no pores or cracks to harbor dirt, grime or bacteria.
♦ It is very attractive and requires minimal care, since it won't chip or easily rust and it takes little seasoning.
♦ It will not affect flavor, as it does not react with acidic foods during food preparation or cooking.
♦ With proper care, it has a useful life expectancy of over 100 years, and it is totally recyclable.

What gives stainless steel its properties?

The chromium content in stainless steel alloys is what generally prevents corrosion. Pure iron, the primary element of stainless steel, is extracted from its natural state as iron ore, it is unstable by itself, and naturally wants to corrode (rust). The chromium helps to procrastinate nature's attempts to combine the pure iron with oxygen and water to form rust.

The chromium works by reacting with oxygen to form a tough, adherent, invisible, passive layer of chromium oxide film on the steel surface. If damaged mechanically or chemically, this film is self healing as long as it has enough oxygen.

Because oxygen is necessary for the reaction, liquids and other foodstuffs stored for a prolonged time in stainless can prevent oxygen contact and thus promote corrosion, as can prolonged contact with household cleaners such as bleach.

Generally, an increase of chromium content improves the corrosion resistance of stainless steels. The addition of nickel is used to raise the general corrosion resistance required in more aggressive usage or conditions. The presence of molybdenum (Mo) improves the localized corrosion resistance, such as against pitting (scarring).

Other alloying metals are also used to improve the structure and properties of stainless steels, such as Titanium, Vanadium and Copper. Non metal additions typically include natural elements such as Carbon & Nitrogen, as well as Silicon.

High-carbon stainless steel contains a minimum of 0.3% carbon. The higher the carbon content, the less formable and the tougher the steel becomes. Its hardness makes it suitable for things such as cutting edges, and other high-wear applications like plow blades. Carbon thus helps makes the edge easier to sharpen, and helps retain a sharp edge longer.

How can stainless steel affect my health?

The principal elements in stainless that have effects on our health are iron, chromium and nickel.

♦ Iron can be very beneficial and a required mineral in a normal diet.
♦ Chromium is also beneficial in small quantities, and you would have to cook four complete meals in the same stainless steel pots every day to come anywhere close to reaching any adverse affects from chromium intake.
♦ Although nickel is poisonous in large quantities, only trace amounts go into the food - not enough to make a difference. The few who are allergic to nickel, however, should avoid using stainless altogether.

What precautions do I need to take when using stainless steel in my kitchen?
♦ To prevent hot spots when using stovetop cookware, it should have a heat diffusing base, either visible or encapsulated, that is made of a better heat-diffusing material, like copper or aluminum. These metals are highly conductive of heat, so use moderate heat to maximize the even spreading of heat, minimize sticking, and to get tastier, more evenly cooked food with less stirring.
♦ Do not store food or liquids in stainless steel cookware after cooking.
♦ To keep the surface smooth and scratch-free, do not use abrasives, bleach or ammonia. See cleaning instructions below.

How do I clean stainless steel cookware?
♦ To remove manufacturer or price stickers from cookware... Soak the area with warm water, then scrape off with your fingernail or with a hard-plastic spatula. A bit of rubbing alcohol, or a citrus oil based cleaner, will remove any remaining glue.

♦ When using a pan for the first time... Wash it well with soapy warm water and dry thoroughly. We recommend washing by hand.

♦ Whitish or chalkish deposits inside pan... Remove calcium deposits by boiling water with some white vinegar, allowing your pan to cool, then washing it with warm, soapy water. Help prevent white spots and pitting by adding salt to your cookware only after the water has reached a boil.

♦ Burnt food is stuck in pan... Cover the stuck foodstuffs with warm soapy water, allow to soak for some time, then boil for 10 minutes, allow it to cool, then use a soft cloth, or a nylon scourer if stubborn, and warm, soapy water.

♦ Still not clean out of the dishwasher... You might select a Pre-wash cycle if your pan's instructions indicate it is safe to clean in the dishwasher.

♦ Spills or overflows... Wash or clean the exterior before placing it again over heat.

♦ Filled pan left to cool on stove and lid won't come off... Warm the pan, then twist the lid to remove it.

♦ Left empty on heated surface... Allow it to cool slowly; do not immerse it in cold water.

♦ Stainless pan was left on heated surface, liquid has dried and yellow or blue streaks appear... On polished stainless, use a metal cleaner, such as Wenol or Red Bear, with a soft cloth. On satin stainless, use a nylon scourer, such as Scotch-Brite.

♦ Scratches on surface after washing repeatedly... Change your cleaning product to a gentler kind, such as Bon Ami.

♦ Cleaners not recommended for stainless surfaces... Bleach or ammonia should not be used on stainless steel.

How do I clean stainless steel knives?
The easiest and safest way to clean knives is to wipe them during and immediately after use, before food gets a chance to stick and dry on the blade. That's one of the reasons why professional cooks have a dish towel tucked at their waist.

Be sure to use caution when cleaning knives, to prevent cuts. Always draw the knife away from its cutting edge on the towel, starting near the handle. (Use caution.)

How are stainless steels classified?
The three major classes of stainless steel are:
♦ Austenitic: Chromium-nickel-iron alloys with 16-26% chromium, 6-22% nickel (Ni), and low carbon content, with non-magnetic properties (if annealed - working it at low temperatures, then heated and cooled). Nickel increases corrosion resistance. Hardenable by cold-working (worked at low temperatures) as well as tempering (heated then cooled). Type 304 (S30400) or "18/8" (18% chromium 8% nickel), is the most commonly used grade or composition.
♦ Martensitic: Chromium-iron alloys with 10.5-17% chromium and carefully controlled carbon content, hardenable by quenching (quickly cooled in water or oil) and tempering (heated then cooled). It has magnetic properties. Commonly used in knives. Martensitic grades are strong and hard, but are brittle and difficult to form and weld. Type 420 (S42000) is a typical example.
♦ Ferritic: Chromium-iron alloys with 17-27% chromium and low carbon content, with magnetic properties. Cooking utensils made of this type contain the higher chromium levels. Type 430 is the most commonly used ferritic.
Two additional classes worth mentioning include Duplex (with austenitic and ferritic structures), and Precipitation Hardening stainless steel, used in certain extreme conditions.

How are different classes of stainless steels used?
The austenitic microstructure is most commonly used for knives and cooking utensils. It is very tough, hardened through a process that consists of heating, cooling and heating. It resists scaling and retains strength at high temperatures.

Both ferritics and austenitics are used in kitchenware and household appliances. Austenitics are preferred in the food industry and beverage equipment due to the superior corrosion resistance and ease of cleaning. Type 301, for example, is an austenitic stainless steel, with 17% chromium, 7% nickel, and .05% carbon, and is widely used for institutional food preparation utensils.

You can easily make do with the lesser quality cookware for most oven use. For stovetop cooking, however, don't skimp on quality; buy only the better ones. Most manufacturers of high quality cookware use stainless steel similar to the Type 304 grade, with thick heat diffusing bottoms. Metals that provide better diffusion of heat, such as copper and aluminum, are attached to the bottom for heat diffusion, to prevent hot spots and uneven cooking.

Low quality cutlery is generally made out of grades like 409 and 430 (ferritic), while the finest Sheffield cutlery uses specially produced 410 and 420 (martensitic) for the knives, and 304 (austenitic) for the spoons and forks. Grades like the 410/420 can be hardened and tempered so that the knife blades will take a sharp edge, whereas the more ductile 304 stainless is easier to work and therefore more suitable for objects that have to undergo numerous shaping, buffing and grinding processes.

The best quality stainless steel knife blades have a high carbon content, and usually have molybdenum and vanadium in their composition.

Heat treatment of steel

2010-04-09T23:50:00.000-07:00

Heat Treatment is the controlled heating and cooling of metals to alter their physical and mechanical properties without changing the product shape. Heat treatment is sometimes done inadvertently due to manufacturing processes that either heat or cool the metal such as welding or forming.

Heat Treatment is often associated with increasing the strength of material, but it can also be used to alter certain manufacturability objectives such as improve machining, improve formability, restore ductility after a cold working operation. Thus it is a very enabling manufacturing process that can not only help other manufacturing process, but can also improve product performance by increasing strength or other desirable characteristics.Steels are particularly suitable for heat treatment, since they respond well to heat treatment and the commercial use of steels exceeds that of any other material. Steels are heat treated for one of the following reasons:

Softening: Softening is done to reduce strength or hardness, remove residual stresses, improve toughnesss, restore ductility, refine grain size or change the electromagnetic properties of the steel.Restoring ductility or removing residual stresses is a necessary operation when a large amount of cold working is to be performed, such as in a cold-rolling operation or wiredrawing. Annealing — full Process, spheroidizing, normalizing and tempering — austempering, martempering are the principal ways by which steel is softened.

Hardening: Hardening of steels is done to increase the strength and wear properties. One of the pre-requisites for hardening is sufficient carbon and alloy content. If there is sufficient Carbon content then the steel can be directly hardened. Otherwise the surface of the part has to be Carbon enriched using some diffusion treatment hardening techniques.

Material Modification: Heat treatment is used to modify properties of materials in addition to hardening and softening. These processes modify the behavior of the steels in a beneficial manner to maximize service life, e.g., stress relieving, or strength properties, e.g., cryogenic treatment, or some other desirable properties, e.g., spring aging.

Manufacture of Steel

2010-04-09T23:49:00.002-07:00

“Steel has been part of some of the greatest achievements in history: It was the "iron horse" and steel rails that helped carve a nation out of the frontier. Steel is the backbone of bridges, the skeleton of skyscrapers, the framework for automobiles. And at the dawn of the 21st century, it's still revolutionizing the way we live. It is the high-strength, lighter-than-plastic frames for eyeglasses; it's the stronger, more durable frame in housing; it's the high-tech alloy used in the Space Shuttle's solid fuel rocket motor cases; and it's the precise surgical instruments used in hospital operating rooms around the world.” (American Iron and Steel Institute 2002) Yes steel today is in just about everything we use today. Steel too has changed over the years.
“Iron has been a vital material in technology for well over three thousand years. But until the Industrial Revolution, its mining, smelting, and working were largely done by individuals and small groups. Known since ancient times, steel is made by alloying iron with carbon to produce a harder, stronger metal that will take a much keener edge. But steel was very expensive to manufacture by the primitive methods then available, and its use was largely confined to high-value specialty products such as swords and precision instruments.” (Garraty 1991) “Steel making (in the 18th century) was a laborious and time-consuming process. Flat bars of iron were laid in a furnace chest, side by side on a bed of charcoal. The bars were the covered with charcoal, another layer of iron bars was placed on top of that and the process was repeated until the chest was full. It was then placed in the furnace, covered with a layer of sand and cooked red-hot for a week. During this time the carbon from the charcoal was absorbed into the outer layers of the iron, the carbonized areas forming blisters on the surface of the bars. When the chest was removed and had cooled down, these blisters were hammered off, and the pieces reheated and hammered together. The resultant “blister” steel was brittle and difficult to work.” (Burke 1996) The Blast furnace technique came some time after this. The blast furnace, which consisted of blowing steam or air through molten iron, had become widely used by the ninetieth century. Along came a man by the name Henry Bessemer who would invent a new way to produce steel using the blast method called the Bessemer process, “the most important technique for making steel in the nineteenth century.” (Misa 1995) He first came across this while melting gun metal down. “Bessemer built a crucible with a blow pipe extended into its center. Into the crucible he poured about 10 pounds of unrefined pig iron and then placed the apparatus into a hot furnace; after 30 minutes of blowing air into the metal, he found the crude iron had become malleable iron. This experiment proved air could decarburize pig iron, turning it into a useful product, yet the furnace surrounding the crucible still consumed copious amounts of fuel. Bessemer's real insight was to get rid of the furnace entirely. For this he built a four-foot tall, open-mouthed cylinder with openings, or tuyères, to blow air into the metal from the bottom.” (Misa 1995) “Acceptance of the process was slow at first, so that by 1870 the annual output of Bessemer steel in the United States was a mere 42,000 tons. Production grew rapidly thereafter, rising to 1.2 million tons in 1880. The principal application of Bessemer steel in the 19th century was for the manufacture of railroad rails, which proved far more durable than iron rails. By the 1890s virtually no more iron rails were being produced.”

Basic Oxygen-Furnace Process
The basic oxygen furnace, roughly resembling the Bessemer converter, is first tilted to receive the scrap and hot-metal charge, then brought upright for the blow. An oxygen lance is lowered into the vessel to a point about 2.5 m (6 ft) above the charge materials. Oxygen under pressure is blown into the furnace for a predetermined length of time, usually 20 to 22 minutes. Consumption of oxygen averages 50 cu m (1766 cu ft) per ton of steel produced. The time to charge, test, and tap is generally equal to the blowing interval: a full cycle is about 45 minutes.

The Electric-Arc Furnace
A large bucket of scrap is charged into the open top of the furnace when the roof assembly has been swung out of the way. With the assembly back in place, three carbon electrodes are lowered through holes in the roof until they are in near contact with the charge. When the power is switched on, arc temperatures approaching 3,300 degrees C (6,000 degrees F) produce a rapid melting of the charge. A second bucket of scrap is usually needed to meet the desired heat weight. Oxygen is often used to accelerate scrap meltdown. When the specified steel requirements are met, the furnace is tilted to tap the heat into a waiting ladle.

Properties of Iron

2010-04-09T23:49:00.001-07:00

Iron is a shiny, bright white metal that is soft, malleable, ductile and strong. Its surface is usually discolored by corrosion, since it combines readily with the oxygen of the air in the presence of moisture. In absolutely dry air, it does not rust. The oxide that is produced is crumbly and soft, giving no protection to the base metal, which eventually rusts away. It is found in nature as the metal only in meteorites and in very rare circumstances where iron minerals have been reduced by environmental factors. Masses up to 25 tons in weight have been found in West Greenland. Practically, it is always obtained from ores that are usually the oxides, and occasionally the carbonate, as low in sulphur and phosphorus as possible. The plentiful iron pyrite, FeS₂ is not an acceptable ore because sulphur is a deleterious impurity in iron, and expensive to remove in refining. Iron is the fourth most plentiful element in the earth's crust (4.6%), but is so widely disseminated that it can be obtained only from ores in which iron has been specially concentrated. Much of this concentration, incidentally, occurred very early in the earth's history when iron removed from the atmosphere the little oxygen that it then contained, possibly with the help of the earliest forms of life.

A clean surface of cobalt is tinged with pink, nickel with yellow. Neither rusts as vigorously as iron, since the oxide layers are more protective and adherent. Nickel displays a resistant bright surface that takes a high polish. It is generally used as an undercoat for chromium plating, since chromium is not suitable by itself on iron, as the electrodeposited film is not continuous.

Iron has atomic number 26, atomic weight 55.85, and stable isotopes 54 (5.9%), 56 (91.6%), 57 (2.2%) and 58 (0.33%). Its electron configuration is Ar3d⁶4s², and its first and second ionization potentials are 7.87V and 16.18V. With its neighbors cobalt (Z=27) and nickel (Z=28), it is one of the "iron triad" of similar metals. It is in the center of the periodic table, in the region of "transition metals" where a d-shell of electrons is being filled. The 4s electrons are actually more stable than the 3d electrons, so the d-electrons are actually on the outside of the atom. The d-shell can hold 10 electrons, and as it becomes nearly filled, drops below the 4s electrons in energy. All these atoms filling d-shells make metals that are very much alike; if the d-electrons were more inside, these metals would be even more alike than they are. More will be said in connection with magnetism, in which these electrons play leading roles.

At room temperature, iron is in the form of ferrite, or α-iron, a body-centered cubic structure. The density of α-iron is 7.86 g/cc. At 910°C it changes to γ-iron, which is face-centered cubic and somewhat softer. At 1535°C iron melts, and boils at 3000°C. For more information on iron structures and the iron-carbon phase diagram, see Phase Rules!. Cobalt melts at 1480°C, nickel at 1455°C. The specific heat of any of the three metals is about 0.107 cal/g-K. The thermal conductivities of Fe, Co and Ni are 3.37, 3.81 and 4.19 cal/s-cm-K. Their electrical resistivities are 9.71, 6.24 and 6.84 μΩ-cm. These are "worse" than those of copper by factors of only 4 to 6, so the iron metals are very good conductors of electricity and heat. Comparing the numbers shows how similar these metals are in their physical properties. I have not heard whether cobalt and nickel make useful alloys with carbon, as iron does. They are much too expensive to use as structural metals, other than as alloying elements or coatings.

Varieties of Iron

2010-04-09T23:48:00.000-07:00

Cast iron
The molten iron from the bottom of the furnace can be used ascast iron.
Cast iron is very runny when it is molten and doesn't shrink much when it solidifies. It is therefore ideal for making castings - hence its name. However, it is very impure, containing about 4% of carbon. This carbon makes it very hard, but also very brittle. If you hit it hard, it tends to shatter rather than bend or dent.
Cast iron is used for things like manhole covers, guttering and drainpipes, cylinder blocks in car engines, Aga-type cookers, and very expensive and very heavy cookware.
Steel
Most of the molten iron from a Blast Furnace is used to make one of a number of types of steel. There isn't just one substance called steel - they are a family of alloys of iron with carbon or various metals. More about this later . . .
Steel-making: the basic oxygen process
Impurities in the iron from the Blast Furnace include carbon, sulphur, phosphorus and silicon. These have to be removed.
Removal of sulphur
Sulphur has to be removed first in a separate process.Magnesium powder is blown through the molten iron and the sulphur reacts with it to form magnesium sulphide. This forms a slag on top of the iron and can be removed.
Removal of carbon etc
The still impure molten iron is mixed with scrap iron (from recycling) and oxygen is blown on to the mixture. The oxygen reacts with the remaining impurities to form various oxides.
The carbon forms carbon monoxide. Since this is a gas it removes itself from the iron! This carbon monoxide can be cleaned and used as a fuel gas.
Elements like phosphorus and silicon react with the oxygen to form acidic oxides. These are removed using quicklime (calcium oxide) which is added to the furnace during the oxygen blow. They react to form compounds such as calcium silicate or calcium phosphate which form a slag on top of the iron.
Types of iron and steel
Cast iron has already been mentioned above. This section deals with the types of iron and steel which are produced as a result of the steel-making process.
Wrought iron
If all the carbon is removed from the iron to give high purity iron, it is known as wrought iron. Wrought iron is quite soft and easily worked and has little structural strength. It was once used to make decorative gates and railings, but these days mild steel is normally used instead.
Mild steel
Mild steel is iron containing up to about 0.25% of carbon. The presence of the carbon makes the steel stronger and harder than pure iron. The higher the percentage of carbon, the harder the steel becomes.
Mild steel is used for lots of things - nails, wire, car bodies, ship building, girders and bridges amongst others.
High carbon steel
High carbon steel contains up to about 1.5% of carbon. The presence of the extra carbon makes it very hard, but it also makes it more brittle. High carbon steel is used for cutting tools and masonry nails (nails designed to be driven into concrete blocks or brickwork without bending). You have to be careful with high carbon steel because it tends to fracture rather than bend if you mistreat it.
Special steels
These are iron alloyed with other metals. For example:
iron mixed with special properties uses include
stainless steel chromium and nickel resists corrosion cutlery, cooking utensils, kitchen sinks, industrial equipment for food and drink processing
titanium steel titanium withstands high temperatures gas turbines, spacecraft
manganese steel manganese very hard rock-breaking machinery, some railway track (e.g. points), military helmets

Occurrence and extraction of iron

2010-04-09T23:47:00.000-07:00

Iron is the most abundant metal which occurs in the earth's crust. There are two forms of iron - cast iron and wrought iron - cast iron is the least pure form of iron whereas wrought iron is the purest form of iron. There are many ores of iron. Among all the ores hematite and magnetite are the important ones. Hematite is mostly found in the northern region in India whereas magnet is found in the southern states.

Extraction

Extraction of Iron is done in many steps like oxidation, combustion, fusion, reduction, etc. During extraction cast iron is formed first which is then converted to wrought iron. Hematite is the ore that is used for extraction of cast iron. The ore is crushed into small pieces and is washed with water to remove the sand particles. Then the washed ore is heated in the presence of air. This process removes the moisture and is called as calcination. In this process, sulphur and phosphorus forms oxides. Carbonate forms oxide and ferrous oxide converts into ferric oxide.

Blast furnace is used in the extraction of iron, which is made of steel lined with bricks. The ore, coke and limestone are sent into this furnace from top. The furnace has an inlet for hot air and two outlets for slag and molten iron. The coke that is sent in burns and produces carbon dioxide. This CO₂ reduces to CO in presence of coke.

The limestone subjected into the furnace decomposes and produce CaO. This CaO later combines with silica and forms slag.

Molten stag formed is lighter and is removed out by the outlet produced for it. All the above reactions takes place from the bottom to the middle region of the furnace. Only the reduction of oxides of iron to iron is done at the top of the furnace.

Thus, the iron that is formed melts and moves down to the base of the furnace. This is called as cast iron. This cast iron is again heated with hematite to remove the impurities.

Thus, wrought iron which is the purest form of iron is formed.

Preparation, properties and uses of (i) Calomel (ii) Corrosive Sublimate

2010-04-09T23:46:00.000-07:00

Calomel

Hg₂Cl₂ is known as calomel. It is prepared by heating HgCl₂ and Hg in an iron vessel.
It can also be prepared by mixing mercury salt with chloride ions.
Properties
1) It is a white powder which is insoluble in water.
2) Hg₂Cl₂ on heating dissociates into HgCl₂ and Hg.
2">
Corrosive sublimate
HgCl₂ is a corrosive sublimate, which is prepared by passing chlorine over heated mercury or mercury chloride.
It can also be prepared by heating mercury sulphate with NaCl.
Properties
1) It is a crystalline solid.
2) It is soluble in hot water, ethanol and ether.
3) HgCl₂ reacts with KI and forms a colorless solution known as Nessler's reagent.

Mercury poisoning and uses of Hg

2010-04-09T23:45:00.002-07:00

Mercury poisoningMercury poisoning (also known as hydrargyria ormercurialism) is a disease caused by exposure tomercury or its compounds. Mercury (chemical symbol Hg) is a heavy metal that occurs in several forms, all of which can produce toxic effects in high enough doses. Its zerooxidation state Hg0 exists as vapor or as liquid metal, its mercurous state Hg+ exists as inorganic salts, and its mercuric state Hg2+ may form either inorganic salts ororganomercury compounds; the three groups vary in effects. Toxic effects include damage to the brain, kidney, and lungs.[1] Mercury poisoning can result in several diseases, including acrodynia (pink disease), Hunter-Russell syndrome, and Minamata disease.[2]Symptoms typically include sensory impairment (vision, hearing, speech), disturbed sensation and a lack of coordination. The type and degree of symptoms exhibited depend upon the individual toxin, the dose, and the method and duration of exposure.Uses of HgBeing the only metal which is liquid at room temperature mercury has some specialist uses:It is used in thermometers because it has a large thermal expansion which is constant over a large temperature range although it is being phased out in favour of safer liquids.It is also used in barometers an manometers due to its high density. From this it has also become a way of measuring pressure in millimetres of mercury.It has also been used as liquid electrolyte for the production of chlorine and sodium hydroxide from the electrolysis of brine but is again being phased out in favour of safer alternatives.It is still sometimes used in electrical switches as a liquid contact.Mercury also used to be used as a component for dental amalgams for making fillings for teeth. This process has again been phase out due to health concerns but many people still have mercury containing fillings and crematoria are thought to emit about 5kg of mercury each year simply from dental fillings. The amalgam of 70% silver and 30% tin when mixed with mercury formed a pliable material that could be inserted into the tooth and the amalgam expanded as it dried to fill the entire cavity. However this amalgam has been replaced by a similar one made from 60% silver, 27% tin and 13% copper.

Properties of mercury

2010-04-09T23:45:00.001-07:00

Here are some facts about mercury:

· Symbol: Hg

· Atomic Number: 80

· Atomic Weight: 200.56 g

· Period Number: 6

· Group Number: 12

· Classification: Metallic

· Electron configuration: [Xe]4f(14)5d(10)6s(2)

(Note that there are electrons in the d orbital, which makes mercury a transition metal)

· Crystal Structure: Rhombohedral

· Electrons per energy level: 2, 8, 18, 32, 18, 2.

· Shell Model:

http://environmentalchemistry.com/yogi/periodic/Hg.html#Overview

· Number of Electrons (with no charge): 80

· Number of Neutrons (most common): 121
· Number of Protons: 80
· Filling Orbital: 5d¹⁰
· Valence Electrons: 6s²
· Electron Dot Model:

· Density: 13.55g/cc @ 300K
· Vapor Pressure: .0002 Pa @ -38.7 C
· Melting Point: -38.7 C
· Boiling Point: 357 C

As one can see from the melting and boiling points (-38.7 C and 357 C, respectively), elemental mercury exists as a liquid at room temperature. Liquid mercury is very volatile (in fact the most of any metal), as seen from its very low vapor pressure of .00002 Pa @ -38.7 C. Even though this transition metal is a liquid, it is still conductive, with an electrical conductivity of 0.0104 10⁶/cm and a thermal conducitivity of 0.0834 W/cmK. Excited mercury atoms emit light in visible wavelengths, making it especially useful in light bulb applications.

Mercury readily forms amalgams, or solutions, with other metals. For example, an amalgam of mercury, tin and silver is used in dentistry. This tendency for mercury to form amalgams makes it especially dangerous to be handled by people wearing gold jewelry, as it can diffuse into the gold.

Occurrence and extraction of Hg from Cinnabar

2010-04-09T23:44:00.000-07:00

Mercury is extracted from the ore cinnabar, HgS. Traditionally the ore was heated in a wood fire and the mercury was collected from the ashes. However, modern methods are much more efficient. The cinnabar is crushed and separated, and then it is heated with a stream of air. The reaction is

HgS + O₂ --> (600C) Hg + SO₂

If the ore is especially rich, scrap iron or quicklime can be added to promote the extraction process:

HgS + Fe --> Hg + FeS

4HgS + CaO --> 4Hg + 3CaS + CaSO₄

The crude mercury can also be washed in nitric acid and air to remove oxides and other impurities. More purification can be achieved if the process is performed at lowered pressures.

Galvanization

2010-04-09T23:42:00.002-07:00

Galvanization is a metal coating process in which a ferrous part is coated with a thin layer of zinc. The zinc coating seals the surface of the part from the environment, preventing oxidation and weathering from occurring.

The primary method of galvanization is “hot dip galvanization”, which has been in use for over 150 years. While the idea of coating a part in molten zinc was first proposed by chemist Paul Jacques Malouin in 1742, the process was not put into practice until patented by chemist Stanislas Sorel in 1836. Sorel’s process has changed little since then, and still involves coating a part in molten zinc after cleaning it with an acid solution and coating the part in flux.

Benefits of Galvanizing Metal Parts

Galvanization helps to extend the life of steel parts by providing a barrier between the steel and the atmosphere, preventing iron oxide from forming on the surface of the steel. Galvanization also provides superior corrosion resistance to parts exposed to the environment.

Galvanization provides a cost-effective solution for coating steel parts, specifically those that will receive significant environmental exposure over their lifetime.

Preparation, properties and uses of zinc and white vitriol

2010-04-09T23:42:00.001-07:00

Uses of Zinc

Zinc is an essential trace element, necessary for plants,animals, and microorganisms. Zinc is found in nearly 100 specific enzymes (other sources say 300), serves as structural ions in transcription factors and is stored and transferred in metallothioneins. It is "typically the second most abundant transition metal in organisms" after iron and it is the only metal which appears in all enzyme classes.

In proteins, Zn ions are often coordinated to the amino acid side chains of aspartic acid, glutamic acid, cysteine and histidine. The theoretical and computational description of this zinc binding in proteins (as well as that of other transition metals) is difficult.

There are 2–4 grams of zinc distributed throughout the human body. Most zinc is in the brain, muscle, bones, kidney, and liver, with the highest concentrations in the prostate and parts of the eye. Semen is particularly rich in zinc, which is a key factor in prostate gland function and reproductive organ growth.

In humans, zinc plays "ubiquitous biological roles". It interacts with "a wide range of organicligands", and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression. It also regulates apoptosis. A 2006 study estimated that about 10% of human proteins (2800) potentially bind zinc, in addition to hundreds which transport and traffic zinc; a similar in silico study in the plantArabidopsis thaliana found 2367 zinc-related proteins.

In the brain, zinc is stored in specific synptic vesicles by glutamatergoc neurons and can "modulate brain excitability". It plays a key role in synaptic plasticity and so in learning. However it has been called "the brain's dark horse" since it also can be a neurotoxin, suggesting zinc homeostasis plays a critical role in normal functioning of the brain and central nervous system.

Occurrence and extraction of zinc from zinc blende

2010-04-09T23:40:00.000-07:00

Zinc occurs only in combined state. The important ores of zinc are zinc blende (Zns), calamine etc. These two are the important ores for the extraction of zinc.

Extraction

Zinc blende is crushed, concentrated and heated in air.

Zinc oxide formed above is mixed with coke in a fireclay retort. It is fitted with a condenser. The metal distills and condenses in the retort. The metal obtained is purified by electrolysis.

Position of zinc in periodic table

2010-04-09T23:39:00.000-07:00

Occurrence

Zinc makes up about 75 ppm (0.0075%) of the Earth's crust, making it the 24th most abundant element there. Soil contains 5–770 ppm of zinc with an average of 64 ppm. Seawater has only 30 ppb zinc and the atmosphere contains 0.1–4 µg/m^3.

Sphalerite (ZnS)

The element is normally found in association with other base metals such as copper and lead in ores.Zinc is a chalcophile ("sulfur loving"), meaning the element has a low affinity for oxygen and prefers to bond with sulfur in highly insoluble sulfides. Chalcophiles formed as the crust solidified under the reducing conditions of the early Earth's atmosphere. Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.

Other minerals, from which zinc is extracted, include smithsonite (zinc carbonate), hemimorphite (zinc silicate),wurtzite (another zinc sulfide), and sometimes hydrozincite (basic zinc carbonate). With the exception of wurtzite, all these other minerals were formed as a result of weathering processes on the primordial zinc sulfides.

World zinc resources total about 1.8 gigatonnes. Nearly 200 megatonnes were economically viable in 2008; adding marginally economic and subeconomic reserves to that number, a total reserve base of 500 megatonnes has been identified. Large deposits are in Australia, Canada and the United States with the largest reserves in Iran.^[12]^[15]^[16] At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055. About 346 megatonnes have been extracted throughout history to 2002, and one estimate found that about 109 megatonnes of that remains in use.

[edit]Isotopes

Five isotopes of zinc occur in nature. ⁶⁴Zn is the most abundant isotope (48.63% natural abundance).This isotope has such a long half-life, at 4.3×10¹⁸ a, that its radioactivity can be ignored.Similarly, ⁷⁰Zn (0.6%), with a half life of 1.3×10¹⁶ a is not usually considered to be radioactive. The other isotopes found in nature are ⁶⁶Zn (28%), ⁶⁷Zn (4%) and ⁶⁸Zn (19%).

Several dozen radioisotopes have been characterized. ⁶⁵Zn, which has a half-life of 243.66 days, is the most long-lived isotope, followed by ⁷²Zn with a half-life of 46.5 hours. Zinc has 10 nuclear isomers.^69mZn has the longest half-life, 13.76 h. The superscript m indicates a metastable isotope. The nucleus of a metastable isotope is in an excited state and will return to the ground state by emitting aphoton in the form of a gamma ray. ⁶¹Zn has three excited states and ⁷³Zn has two. The isotopes⁶⁵Zn, ⁷¹Zn, ⁷⁷Zn and ⁷⁸Zn each have only one excited state.

The most common decay mode of a radioisotope of zinc with a mass number lower than 66 is electron capture. The decay product resulting from electron capture is an isotope of copper.

n30Zn + e^⁻ → n29Cu

The most common decay mode of a radioisotope of zinc with mass number higher than 66 is beta decay(β^–), which produces an isotope of gallium.^[20]

n30Zn → n31Ga + e^⁻ + ν_e

Chemistry of (i) blue vitriol (ii) black oxide of copper (iii) red oxide of copper

2010-04-09T23:37:00.002-07:00

Blue vitriol

Copper(II) sulfate is the chemical compoundwith the formula Cu SO₄. This salt exists as a series of compounds that differ in their degree ofhydration. The anhydrous form is a pale green or gray-white powder, whereas the pentahydrate(CuSO₄·5H₂O), the most commonly encountered salt, is bright blue. The anhydrous form occurs as a rare mineral known as chalcocyanite. The hydrated copper sulfate occurs in nature aschalcanthite (pentahydrate), and two more rare ones: bonattite (trihydrate) and boothite (heptahydrate). Archaic names for copper(II) sulfate are "blue vitriol" and "bluestone".^[1]

Preparation

Preparation of copper(II) sulfate by electrolyzing sulfuric acid, using copper electrodes

Since it is available commercially, copper sulfate is usually purchased and not prepared in the laboratory. It can be made by the action of sulfuric acid on a variety of copper(II) compounds, for examplecopper(II) oxide; this oxide can be generated with the addition of hydrogen peroxide to the acid. It may also be prepared by electrolyzing sulfuric acid, using copper electrodes. It can also be prepared by electrolysis of magnesium sulfate [Epsom salts] solution at moderate voltage with a copper anode: this reaction produces hydrogen, copper sulfate solution, and magnesium hydroxide precipitate:

MgSO₄(aq) + 2 H₂O + Cu(s) → H₂(g) + Mg(OH)₂(s) + CuSO₄(aq)

Black oxide of copper

Copper(II) oxide or cupric oxide (CuO) is the higher oxideof copper. As a mineral, it is known as tenorite.

It is a black solid with an ionic structure which melts above 1200 °C with some loss of oxygen. It can be formed by heating copper in air:

2 Cu + O₂ → 2 CuO

Here, it is formed along with copper(I) oxide as a side product; thus, it is better prepared by heating copper(II) nitrate, copper(II) hydroxide or copper(II) carbonate:

2 Cu(NO₃)₂ → 2 CuO + 4 NO₂ + O₂

Cu(OH)₂ (s) → CuO (s) + H₂O (l)

CuCO₃ → CuO + CO₂

Copper(II) oxide is a basic oxide, so it dissolves in mineral acids such as hydrochloric acid, sulfuric acid or nitric acidto give the corresponding copper(II) salts:

CuO + 2 HNO₃ → Cu(NO₃)₂ + H₂O

CuO + 2 HCl → CuCl₂ + H₂O

CuO + H₂SO₄ → CuSO₄ + H₂O

It reacts with concentrated alkali to form the corresponding cuprate salts:

2 XOH + CuO + H₂O → X₂[Cu(OH)₄]

It can also be reduced to copper metal using hydrogen orcarbon monoxide:

CuO + H₂ → Cu + H₂O

CuO + CO → Cu + CO₂

A laboratory method for preparing copper II oxide would be to electrolyze water containing sodium bicarbonate at a moderate voltage with a copper anode, collect the mixture of copper hydroxide, basic copper carbonate, and copper carbonate produced, and heat it.

Uses

Cupric oxide is used as a pigment in ceramics to produce blue, red, and green (and sometimes gray, pink, or black) glazes. It is also used to produce cuprammonium hydroxide solutions, used to makerayon. It is also occasionally used as a dietary supplement in animals, against copper deficiency.^[11]Copper(II) oxide has application as a p-type semiconductor, because it has a narrow band gap of 1.2 eV. It is an abrasive used to polish optical equipment. Cupric oxide can be used to produce dry cell batteries. It has also been used in wet cell batteries as the cathode, with lithium as an anode, and dioxalane mixed with lithium perchlorate as the electrolyte. Copper(II) oxide can be used to produce other copper salts. It is also used when welding with copper alloys.^[12]

Another use for cupric oxide is as a substitute for iron oxide in thermite. This can turn the thermite from an incendiary to a low explosive.

Red oxide of copper

Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu₂O. It is one of the principaloxides of copper. This red-coloured solid is a component of some antifouling paints. The compound can appear either yellow or red, depending on the size of the particles, but both forms degrade to copper(II) oxides in moist air.^[1]Copper(I) oxide is found as the reddish mineral cuprite.

Preparation

Copper(I) oxide may be produced by several methods.^[2]Most straightforwardly, it arises via the oxidation of copper metal:

4 Cu + O₂ → 2 Cu₂O

Additives such as water and acids affect the rate of this process as well as the further oxidation to copper(II) oxides. It is also produced commercially by reduction of copper(II) solutions with sulfur dioxide. Aqueous cuprous chloride solutions react with base to give the same material. In all cases, the color is highly sensitive to the procedural details.

Formation of copper(I) oxide is the basis of the Fehling's test and Benedict's test for reducing sugars. These sugars reduce an alkaline solution of a copper(II) salt, giving a bright red precipitate of Cu₂O.

It forms on silver-plated copper parts exposed to moisture when the silver layer is porous or damaged. This kind ofcorrosion is known as red plague.

Applications

Cuprous oxide is commonly used as a pigment, a fungicide, and an antifouling agent for marine paints.Rectifier diodes based on this material have been used industrially as early as 1924,long before siliconbecame the standard.

Properties and uses of copper

2010-04-09T23:37:00.001-07:00

Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable, and a freshly-exposed surface has a pinkish or peachy color. It is used as a thermal conductor, anelectrical conductor, a building material, and a constituent of various metal alloys.

A copper disc made bycontinuous casting andetching.

Copper metal and alloyshave been used for thousands of years. In the Roman era, copper was principally mined onCyprus, hence the origin of the name of the metal as Cyprium, "metal of Cyprus", later shortened to Cuprum. There may be insufficient reserves to sustain current high rates of copper consumption. Some countries, such as Chileand the United States, still have sizable reserves of the metal which are extracted through large open pit mines.

Copper compounds are known in several oxidation states, usually +2, where they often impart blue or green colors to natural minerals such as turquoise and have been used historically widely as pigments. Copper metal architectural structures and statuary eventually corrode to acquire a characteristic green patina. Copper as both metal and pigmented salt, has a significant presence in decorative art.

Copper(II) ions (Cu²⁺) are soluble in water, where they function at low concentration as bacteriostatic substances, fungicides, and wood preservatives. For this reason, copper metal can be used as an anti-germ surface that can add to the anti-bacterial and antimicrobial features of buildings such as hospitals. In sufficient amounts, copper salts can be poisonous to higher organisms as well. However, despite universal toxicity at high concentrations, the Cu²⁺ ion at lower concentrations is an essential trace nutrient to all higher plant and animal life. In animals, including humans, it is found widely in tissues, with concentration in liver, muscle, and bone. It functions as a co-factor in various enzymes and in copper-based pigments.

Applications

Copper is malleable and ductile and is a good conductor of both heat and electricity.

The purity of copper is expressed as 4N for 99.99% pure or 7N for 99.99999% pure. The numeral gives the number of nines after the decimal point when expressed as a decimal (e.g. 4N means 0.9999, or 99.99%). Copper is often too soft for its applications, so it is incorporated in numerous alloys. For example, brass is a copper-zinc alloy, and bronze is a copper-tin alloy.

It is used extensively, in products such as:

Piping

Assorted copper fittings

including water supply.
used extensively in refrigeration and air conditioningequipment because of its ease of fabrication and soldering, as well as high conductivity to heat.

Electrical applications

Copper wire
Oxygen-free copper
Electromagnets
Printed circuit boards
Lead free solder, alloyed with tin
Electrical machines, especially electromagnetic motors, generators and transformers
Electrical relays, electrical busbars and electrical switches
Vacuum tubes, cathode ray tubes, and the magnetrons in microwave ovens
Wave guides for microwave radiation
Integrated circuits, increasingly replacing aluminium because of its superior electrical conductivity
As a material in the manufacture of computer heat sinks, as a result of its superior heat dissipation capacity to aluminium

Copper roof on the Minneapolis City Hall, coated with patina

Architecture and industry

While electrical applications use oxygen-free copper, unalloyed copper used in architectural applications is the lower-purty Phosphorus Deoxidized Copper (also called Cu-DHP).^[41]
Copper has been used as water-proof roofing material since ancient times, giving many old buildings their greenish roofs and domes. Initially copper oxide forms, replaced by cuprous and cupric sulfide, and finally bycopper carbonate. The final carbonate patina (termedverdigris) is highly resistant to corrosion.
Statuary: The Statue of Liberty, for example, contains 179,220 pounds (81.29 metric tons) of copper.
Alloyed with nickel, e.g. cupronickel and Monel, used as corrosive resistant materials in shipbuilding.
Watt's steam engine firebox due to superior heat dissipation.
Copper compounds in liquid form are used as a wood preservative, particularly in treating original portion of structures during restoration of damage due to dry rot.
Copper wires may be placed over non-conductive roofing materials to discourage the growth of moss. (Zinc may also be used for this purpose.)

Old copper utensils in a Jerusalem restaurant

Copper is used to prevent a building being directly struck by lightning. High above the roof, copper spikes (lightning rods) are connected to a very thick copper cable which leads to a large metal plate underneath the ground. Thevoltage is dispersed throughout the ground harmlessly, instead of destroying the main structure.^[43]

Household products

Copper plumbing fittings and compression tubes.
Doorknobs and other fixtures in houses.
Roofing, guttering, and rainspouts on buildings.
In cookware, such as frying pans.
Some older flatware: (knives, forks, spoons) contains some copper if made from electroplated nickel silver(EPNS).
Sterling silver, if it is to be used in dinnerware, must contain a few percent copper.
Copper water heating cylinders
Copper range hoods
Copper bath tubs
Copper counters
Copper sinks
Copper slug tape

Coinage

As a component of coins, often as cupronickel alloy, or some form of brass or bronze.
Coins in the following countries all contain copper: European Union (euro),^[44] United States,^[44]^[45]United Kingdom (sterling),^[46] Australia^[47] and New Zealand.^[48]
U.S. nickels are 75.0% copper by weight and only 25.0% nickel.

Biomedical applications

As a biostatic surface in hospitals, and to line parts of ships to protect against barnacles andmussels, originally used pure, but superseded by Muntz metal. Bacteria will not grow on a copper surface because it is biostatic. Copper doorknobs are used by hospitals to reduce the transfer of disease, and Legionnaires' disease is suppressed by copper tubing in air-conditioning systems.
Copper(II) sulfate is used as a fungicide and as algae control in domestic lakes and ponds. It is used in gardening powders and sprays to kill mildew.
Copper-62-PTSM, a complex containing radioactive copper-62, is used as a positron emission tomography radiotracer for heart blood flow measurements.
Copper-64 can be used as a positron emission tomography radiotracer for medical imaging. When complexed with a chelate it can be used to treat cancer through radiation therapy.

Chemical applications

Compounds, such as Fehling's solution, have applications in chemistry.
As a component in ceramic glazes, and to color glass.

Occurrence and extraction of copper form copper pyrites

2010-04-09T23:36:00.000-07:00

Copper occurs both in combined state and free state. It also contains many ores. The important ores of copper are copper pyrites (CuFeS₂), cuprite and copper glance. The copper ores are mostly found in the north of India.

Extraction

The extraction of copper also involves many steps. The ore used for extraction is copper pyrites. This ore is crushed, concentrated and then heated in the presence of air. During heating the moisture gets expelled and the copper pyrites gets converted to ferrous sulphide and cuprous sulphide.

Blast furnace is used to heat the mixture of roasted ore, powdered coke and sand. In the blast furnace oxidation reactions takes place.

Ferrous sulphide forms ferrous oxide which combines with silica and forms the slag.

Cuprous sulphide forms cuprous oxide which is partially converted to cuprous sulphide.

This cuprous sulphide contains some amount of ferrous sulphide and this is called matte. Matte is removed from the base outlet of blast furnace. The removed matte is shifted into Bessemer converter which is lined inside with magnesium oxide. This converter has pipes through which hot air and SiO₂are sent in. In this converter Cu₂S converts to Cu₂O and FeS converts to FeO. The ferrous oxide forms slag with SiO₂. The cuprous oxide formed reacts with Cu₂S and forms copper.

The copper thus formed is to be purified by electrolysis.

Position of copper in periodic table

2010-04-09T23:35:00.000-07:00

Copper occupies the same family of the periodic table as silver and gold, since they each have one s-orbital electron on top of a filled electron shell which forms metallic bonds. This similarity in electron structure makes them similar in many characteristics. All have very high thermal and electrical conductivity, and all are malleable metals. Among pure metals at room temperature, copper has the second highest electrical and thermal conductivity, after silver.

Basic information about copper.

Name: Copper
Symbol: Cu
Atomic number: 29
Atomic weight: 63.546 (3) [see note r]
Standard state: solid at 298 K
CAS Registry ID: 7440-50-8

CHEM-GUIDE

Namaste & Welcome !!

Uses of halogens

Preparation and uses of i. Silver chloride ii. Silver nitrate

Properties

Properties

Extraction of Silver by cyanide process and its uses

Extraction

Structure and uses of green vitriol, Ferric chloride, Mohr's salt

Nutritional supplement

Reactions

Laboratory use

Uses and biological importance of iron

Rusting of iron and its prevention

Stainless steel

Heat treatment of steel

Manufacture of Steel

Properties of Iron

Varieties of Iron

Occurrence and extraction of iron

Extraction

Preparation, properties and uses of (i) Calomel (ii) Corrosive Sublimate

Properties

Corrosive sublimate

Properties

Mercury poisoning and uses of Hg

Properties of mercury

Occurrence and extraction of Hg from Cinnabar

Galvanization

Benefits of Galvanizing Metal Parts

Preparation, properties and uses of zinc and white vitriol

Occurrence and extraction of zinc from zinc blende

Extraction

Position of zinc in periodic table

Occurrence

[edit]Isotopes

Chemistry of (i) blue vitriol (ii) black oxide of copper (iii) red oxide of copper

Preparation

Uses

Preparation

Copper(I) oxide may be produced by several methods.[2]Most straightforwardly, it arises via the oxidation of copper metal:

Applications

Properties and uses of copper

Applications

Piping

Electrical applications

Architecture and industry

Household products

Coinage

Biomedical applications

Chemical applications

Occurrence and extraction of copper form copper pyrites

Extraction

Position of copper in periodic table

Copper(I) oxide may be produced by several methods.^[2]Most straightforwardly, it arises via the oxidation of copper metal: