What is a Chemical Warfare?


          A chemical warfare involves the use of chemical substances to kill or cause physical harm to the enemy or to destroy its food supply. The intention behind using these weapons is to destroy life without damaging any property. In the ethics of modern warfare use of chemical substances are prohibited.



          This type of warfare has continued over the ages — in fact throughout the human history. There is evidence to prove that the ancient Greek warriors had developed chemical fire bombs and used them against the enemies. In recent times, chemical warfare found an extensive use in World War I (1914-1918). In January 1915, the Germans used chlorine gas against the Russians in Poland — although too little effect. But on 22 April 1915, using similar weapons they scored a tactical victory against the French and the British in Flanders that went beyond their expectations. The chlorine gas affected the lungs of soldiers causing choking and making it difficult for them to breathe. It, in fact, disabled so many soldiers that the Germans later devoted much more time for research on harmful gases.



          In 1917 the Germans introduced the mustard gas. Its special feature is that unlike other gases it directly affects the skin and is absorbed through it thus rendering the gas masks useless. It causes blisters on the skin and irritation to the lungs. Thus in the war more soldiers died from this gas than any other gas.



          After World War I, a major breakthrough was achieved by Germany in the development of nerve gases. They were far more toxic than the gases used in World War I, but were never used. In fact the nerve gases interfere with the normal activity of the nerve cells, and can cause convulsions, vomiting and death. Many such gases are tasteless, odourless and colourless.



          Many other such poisonous gases have reportedly been produced in various countries. These also include blood gases which interfere with the normal functioning of the blood and utilization of oxygen by the body tissues.



          Other gases, such as tear gas, have a temporary effect. Tear gas causes excess tears, irritation the nose, mouth and eyes and violent coughing. It is used by police in controlling crowds and riots, but has been used occasionally by military also.



         Gas warfare is potentially so harmful that there have been international agreements to prevent its use. Hence the use of harmful gases has been kept to the minimum since World War I. However, nerve gases were said to have been used in the gulf war during 1991.



          Some chemicals are used to kill plants to destroy the food reserve. These defoliants were widely used in the Korean and Vietnamese conflicts. 


What are solar flares?


          A solar flare is defined as a sudden intense brightening of a small part of the sun’s chromosphere near a sunspot group. The brightness of the flare may be five times that of the associated plage or facula. The flare develops in a matter of a few minutes and may last for several hours. In a large solar flare, tremendous energy to the extent of ergs is released.



          Solar flares occur only as a result of sunspot activity. Practically all sunspots produce some flares but certain spots are much more active. Their source of energy is the magnetic fields surrounding the sunspots.



          Such flares are rarely seen in white light because they are an atmospheric phenomenon, with such low density that they’re transparent. On the other hand, their temperature is so high that in the ultraviolet zone, they may equal the intensity of the entire Sun. However, because the flares are most easily observed in Ha (H-alpha) and because the Ha brightening is an extremely accurate indicator, they can be studied well.



          Solar flares emit ultraviolet radiations and X-rays. They also emit great amount of energetic particles and cosmic rays. The particles travel much slower than the light of the flare and reach the vicinity of Earth a day or two later. They pose a potential radiation hazard to human beings in space. During solar flares, jets of particles known as the solar wind, and strong radio frequency electromagnetic radiations are emitted which disrupt radio communications and cause auroras.



          Flares also produce intense streams of electrons. These travel at about one third of the speed of light. 


What is a poison?

            A poison is a toxic substance that is damaging to life. When taken in excess, it causes irritation, soreness, roughness or redness, vomiting, nausea etc. Sometimes it can cause internal injury, sickness or even death. Poisons may be natural substances produced by living things like animals or plants. They can also be artificially made from different chemicals. Some minerals are also poisonous.



            There are different types of poisons: corrosive, irritant, systematic, gas poisons and food poisons. 





            The corrosive poisons kill the living tissues. In case of human beings it may damage the lining of the mouth or throat. Sodium hydroxide, some acids and phenols, are examples of corrosive poisons.



           



            The irritant poisons cause swelling and soreness of the muscous membranes. They may also damage the stomach, intestines or nerve centres. Some medicines, when taken in excess dosage, can act as irritant poisons. Some other can, make the body bleed inside. 


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What are the methods of sewage disposal?

          Sewage is a watery mixture of all wastes that come from different sources which include residential as well as non-residential places. It includes human wastes, soapy and dirty water from sinks and bathrooms, food scrabs and other garbage washed down the drains. More than 90 percent of sewage is the water used to wash the wastes away. A household might produce hundreds of gallons of sewage every day. Do you know how it is disposed?



          There are two ways of disposing the sewage. It can be stored in underground septic tanks until it gets soaked into the soil, or it can be dumped into rivers and oceans. The big cities may produce millions of gallons of sewage every day. Since the ground doesn’t have enough space for all of it, the cities are forced to dump the wastes into rivers and oceans. Unfortunately, this causes serious pollution.



          The sewage may be carried from homes in underground pipes which lead to a sewage treatment plant. Once in the plant, the sewage undergoes primary treatment. It removes the solid wastes by allowing them to sink to the bottom of a large tank. The liquid sewage is drained off the top and the solid sewage is collected from the bottom and burnt. Some sewage plants provide for only primary treatment. The liquid sewage is then poured into rivers.



          Most modern sewage treatment plants have equipments for a secondary treatment which remove the harmful germs and the floating wastes. The sewage is mixed with those bacteria that breakdown the wastes into harmless products. This process of destroying the waste kills off many germs. Large amounts of chlorine are then mixed into the water to kill all the remaining germs and other micro-organisms.



          Today many modern treatment plants have introduced a third step also. It removes the nutrients and chemicals that make water undrinkable. So, when the water passes through a tertiary treatment plant, it gets clean enough and can be drunk.





 


How is cheese made?


          Today, there are a variety of cheese made from the milk of different animals such as cow, goat, sheep, buffalo, mare, llama and yak. There are over 240 different kinds of French cheese because the French are the greatest cheese-eaters. They eat more than 18 kg cheese per person every year. The different varieties of cheese can be clubbed under two groups - hard and soft.



          Hard cheese is made from pasteurized whole milk ripened with a culture of lactic acid bacteria that converts some of the lactose into lactic acid. The milk proteins are then coagulated into a sort of ‘curd’ by the addition of rennet. Rennet contains the enzymes, rennin and pepsin, obtained from the stomach of young calves. This is useful to transform curdling milk to junket (junket is a custard like pudding made of milk). The junket is then cut into cubes to allow the liquid residue (whey) to separate. It is then heated to 38°C to drain off whatever whey might be left. It is then cut into blocks and pressed to remove the last traces of whey. These blocks of dry ‘curd’ are cut into small pieces and then salt is added to act as a preservative and to improve its flavour. Finally the cheese is produced by pressing the salted curd in moulds for about 48 hours and then ripening it under controlled temperature and humidity for three to six months. The ripening occurs on account of bacterial and enzyme action.



          Soft cheese is made in a similar way but with a major difference: the whey is left to drain off from the curd by gravity without applying any pressure or heat. The resulting cheese has high moisture content, between 50 to 70 percent, and they have mould cultures that excrete enzymes to give them the characteristic flavour. 


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What is ozone gas?


          Ozone is a form of oxygen in which each molecule contains three atoms of oxygen instead of the usual two. Its chemical formula is  and the three atoms are arranged in a triangular shape. This means that although its molecules contain only oxygen atoms, their number and arrangement differ from that of oxygen gas.



          Ozone is light blue in colour and has a strong odour. The characteristic smell can be experienced near running electric motors. It is poisonous in nature, differing considerably from oxygen in its chemical properties. It is found in the atmosphere in very small quantities, the highest concentration being at high altitudes where it is formed by the reaction of ultraviolet rays on oxygen.



          To obtain ozone, ordinary oxygen is passed through a tube where it is subjected to a silent electrical discharge. The electrodes are covered with insulating materials (glass or mica) so that the discharge currents are kept low, and high voltage pulses are supplied between the electrodes. This method has to be used so that oxygen acquires the energy it needs to form ozone but at the same time ozone does not become so hot that the molecules again break up into ordinary oxygen.



          Ozone is a powerful oxidizing agent. It is used to sterilize water, to purify air, to decolourize foods, and act as bleach. Its ozonide-forming property is used in several industrial processes in the manufacture of drugs and plasticizing materials.



          An ozone layer in the atmosphere absorbs much of the sun's harmful ultraviolet rays and consequently saves the animal and plant lives on Earth. This is due to the fact that the ultraviolet rays spoil the vegetation and cause diseases like cataract and skin cancer. Recently the discovery of holes in the ozone layer created a great concern and hence the use of substances like chlorofluorocarbon (CFC), which are responsible for the depletion of the ozone layer, is being gradually eliminated.



 


What are pesticides?


            Any plant or animal that occurs in such abundance as to pose a distinct threat to man or his interests is called a pest. And the chemicals used for mitigation, control or elimination of such plants or animals are known as pesticides. Today we have algaecides, defoliants, herbicides, plant growth regulators and fungicides in use to control the growth of undesirable plants which compete with crops or other useful plants. Attractants, insecticides, miticides or acaricides, molluscicides, nematocides, repellents and rodenticides are used to reduce parasitism and disease-transmitting organisms in animals, crops, plants, foods, textiles and human beings.



            Most of the pesticides are chemical compounds and act in a similar fashion, i.e. by blocking some metabolic process. They, however, differ in composition, potency, mode of action, speed of effect. So different pesticides are used at different stages of infection. 


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What is Carbon Dating?

          Man’s curiosity has always led to the opening of new vistas in every field thus contributing to the development of science and widening the sphere of knowledge. And the curiosity of man to determine the age and period of existence of different objects that were once alive resulted in the technique of carbon dating. Through carbon dating process the age of different fossils of ancient plants and animals can be determined by finding out how long ago they lived.



          Radio-carbon and carbon-14 dating are two other names used for carbon dating. Now comes the question: what is this process and how does it help to estimate the age of the objects?



          Like all materials, carbon is made up of atoms. A small fraction of all carbon atoms are distinct from the others in the sense that they are radioactive and hence unstable. These atoms have 13 to 14 particles whereas the majority contains 12 particles. Carbon-14 is radioactive because it is unstable and breaks down, or decays very slowly into other elements. After the break up, they give up a burst of nuclear radiation.



          There is a regular intake of fresh supply of carbon from the atmosphere by all living things. They get rid of some carbon every time they breathe out but when they die some carbon is trapped inside. Some of the trapped carbon is radioactive, the most prominent being carbon-14. The carbon-14 inside them begins to decay at a constant rate. The age of the object is discovered by measuring the amount of carbon-14 still contained in the object. Age is estimated by working out how long ago death occurred. Archaeologists follow this process while determining the age of the objects discovered by them. The method is explained in the following paragraph.



          The time taken for half the atoms in any quantity of a radioactive substance to decay is called half-life of the substance. For example, when a tree is cut down, it ceases to acquire further carbon-14 atoms. Therefore, by comparing the radioactivity of a modern piece of wood with that of a specimen of some unknown age, the length of time that has elapsed since the latter’s death can be estimated.



          It is interesting to note that earlier the dating of some rocks were determined by scientists by observing the Uranium 238 element present in the rocks. The element Uranium 238 is known to have a half-life of 4,500 million years. It means that a given quantity of the material will be reduced by one-half in 4,500 million years. The age of the stones or rocks which contain Uranium 238 can be determined directly. But the radio-carbon process has replaced this method now.



          The age of old bones, wood, mummies and even old cloth (because the fibers come from dead plants) are estimated this way.



 



 


How are different paints made?


          Paint is a mixture of one or more coloured powders and a liquid. The coloured powder is called a pigment. The liquid is called a vehicle or binder. The vehicle carries the pigment and allows it to spread over the surface. Many vehicles contain a solvent or thinner.



          There are basically two types of pigments – prime pigment and inert pigment. Prime pigments give the paint its colour, and inert pigments like calcium carbonate, clay, mica or talc make the paint durable.



          Vehicles include oils, varnishes, latex and various types of resins. When a vehicle comes in contact with air, it dries and hardens. This makes the pigment bind with the surface. 





          There are various types of paints in common use today. The paints often used on walls and roofs are oil-based. Such paints serve to protect wood and metals. Latex paints include wall paints and masonry paints. Many masonry paints are produced with substances like polyvinyl acetate or acrylic emulsions. Lacquers are often used to paint the automobiles. It is made up of a solution of resins in a solvent. The solvent dries up after the laquer is put on. Now we also have fire-retardant paints that protect against any likely damage due to fire. Heat resisting paints are used to cover warm and hot surfaces.



          Then there are cement water paints that add colour to cement surfaces, such as a basement floor. In the metallic paints, aluminium or bronze powder is used as an ingredient. Enamel paints contain small amounts of prime pigments. They are often used in bathrooms and kitchens.



          Paint is manufactured in the following process in the paint factories. A small amount of the vehicle is put into a large mechanical mixer. Then powdered pigment is slowly added to the vehicle. Thus a heavy paste of these two items is made. Now the paste is put into a grinder to break-up the pigment particles, and scatter them throughout the vehicle. This operation is followed by ‘thinning’ and ‘drying’. Now, the paint is poured until the solution is thin enough for use. Tinting is the next process. A tinter adds a small amount of pigment to give the paint the exact colour and shade desired. The final steps include straining and packaging. The paint is strained through a filter to remove any solid bits, dust or dirt. It is then poured into a filling tank, and finally into metal cans in which it is sold.  


How do detergents perform the cleaning action?


The word ‘detergent’ means any substance that cleans things. But today the word is usually used to mean synthetic or man-made detergents such as washing powders.



A detergent is an organic substance composed of carbon, oxygen, sulphur and hydrogen compounds. When combined with water it helps to clean soiled materials. The ordinary soap is a type of detergent, but it has a different chemical composition. The household detergents, used mainly for cleaning clothes and utensils, come in powder, flake or liquid form.



The first detergent was developed in 1916 by a German scientist called Fritz Gunther. Since then their use has been on the constant increase.



All the detergents contain a basic cleaning agent called a surfactant or surface-active agent. The surfactant molecules attach themselves to dirt particles in soiled materials like cloth etc. They pry the dirt particles from the cloth and surround the particles with a layer of water that allows them to be carried away. The surfactants that are made by treating beef fat or tallow with various chemicals increase the wetting ability of water by lowering its surface tension. The surface tension is the force that keeps water molecules separate and help to move deeper into soiled materials. This helps remove deep-seated dirt particles in fabrics. For example, surfactants also help detergents create lather and suds. Contrary to the popular belief, lather and suds have very little to do with the cleaning ability of a detergent.



Most of the detergents contain many other agents besides surfactants, including bleaches, fabric brighteners, builders and stabilizers. They also contain anti-redeposition agents that prevent removed dirt particles from returning to the cleaned material.



The surfactants can be divided into three main groups: anionic, which become negatively charged ions when in solution; cationic - which form positive ions in solution; and non-ionic which do not become ionized. Detergents may be anionic, cationic or non-ionic or mixture of two or more type of surfactant.



 


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What is a welding torch?

               A welding torch is a mechanical device that produces a hot flame by mixing gases for the welding or cutting of metals. This device is used to join metal surfaces by raising the temperature high enough so as to melt the joining ends and then fuse them with or without a filter metal. After the heat is removed the joint solidifies and fuse permanently. This torch usually produces a flame temperature of 2750°C to 3300°C by mixing acetylene and pure commercial oxygen which is sufficient to melt the metal locally. The torch thoroughly mixes the two gases and has facilities to adjust and regulate the flame. 





               Welding torches are of two types: low pressure torch and high pressure torch. On a low pressure or injector torch, acetylene enters a mixing chamber where it meets a jet of high pressure oxygen. The amount of acetylene drawn into flame is controlled by the velocity of this oxygen jet. In a high pressure torch both the gases are delivered under pressure. The heat generated at the work is controlled principally by the size of the nozzle or the tip fitted onto the torch. The larger the tip, the greater the gas pressure. Small flames are used with thin-gauge metals. Larger flames are necessary for thick metal parts.



               A welding torch mixes the fuel and gas internally and well ahead of the flame. For cutting, the torch delivers an additional jet of pure oxygen to the centre of the flame. The oxyacetylene flame produced by mixed gases raises the metal to its ignition temperature. The central oxygen jet oxidizes the metal, the oxide being blown away by the velocity of the gas jet to leave a narrow slit or kerf. The temperature for the cutting action, once initiated, is maintained by the oxidation of the metal. Nowadays automatic torches have been developed for precision, cutting and welding.   


How do we measure the hardness of materials?


            Hardness is a characteristic property of the solid objects. It is measured by the resistance which the body offers to anything which tends to scratch it. The hardness of the various materials is measured either on the ‘Mohs’ scale or the ‘Knoop’ scale.



            The Mohs’ scale, first devised in 1822 by Friedrich Mohs, measures resistance to indentation as judged by the material that will scratch another. Mohs’ scale is numbered from 1 to 10, that is, it gives ten grades of hardness. In this scale diamond is the hardest material and talc is the softest. Diamond has a hardness of 10 Mohs and talc has a hardness of 1 Mohs.



            Mohs’ scale, which assigns numbers to natural minerals, has been widely accepted and is used by mineralogists. This test, however, is not quantitative. For example, the hardness of sapphire is 9 on the Mohs’ scale; it does not mean that sapphire is 10% softer than diamond.



            The mineralogists carry a box containing pieces of the above minerals for testing samples in the field. For example, if they find a mineral that can be scratched by feldspar but not by appetite, its hardness lies between 5 and 6 on the hardness scale.



            To measure hardness in the Knoop scale, an elongated diamond-shaped indenting device is employed to measure the indentation it makes in a given test material. By this method, the hardness of extremely brittle materials including glass and even diamond can be measured without damaging either the indenter or the test piece. The size of the indentation is taken as a measure of the material’s hardness.



 


What are the different abrasives?


          An abrasive is a substance used for grinding, cutting, scroping or polishing the materials. There are two types of abrasives: natural and artificial abrasives. Natural abrasives include quartz, sandstone, pumice, diamond and corundum; artificial abrasives include rouge, whiting and carborundum.



          Abrasives are available mainly in two forms: paper and grinding wheels. The abrasive paper is made by coating ordinary paper with glue and adding the abrasive material to it. The sandpaper, emery paper, and carborundum paper are made in this way. To make a grinding wheel, abrasive material such as quartz is mixed with clay and water. This mixture is then pressed into the desired size and shape and fired in a furnace. The heat inside the furnance makes a strong bond among the materials put inside the furnance. 





          The fineness or coarseness of the particles used in an abrasive material is described in terms of its ‘grit number’. The abrasive materials with a grit number of 60 are much finer than those with a grit number of 30.



The hardness of an abrasive is also an important factor. It is measured on the Mohs’ scale. The Mohs’ scale ranges from 1 to 10. An abrasive is chosen according to the material to be ground. It should be harder than the material that is to be polished.



          The most widely used abrasives are fused aluminium oxide and silicon carbide. The aluminium oxide is known as alumina. It is used to grind and polish metals like steel, wrought iron and hard bronze. The silicon carbide is known as carborundum. It is made by fusing sand and coke in an electric furnace. Carborundum is used to grind and polish brass, copper, aluminium, stone, glass and ceramics.



          Many varieties of quartz are also important abrasives. Pumice, a volcanic rock, when ground to a fine powder, can be used in scouring powder and soaps. Crystalline iron oxide is used to polish jewellery and glass. It is known as rouge because of its red colour.



          The synthetic diamonds, diamond powders and diamond pastes are also used as abrasives. They are used to make drill bits and cutting wheels. Tungsten carbide is used in the machine tool industry for drilling, cutting and polishing metals. Boron carbide is another important abrasive. It is valuable because it is almost as hard as diamond. It is also used in nuclear reactor as a moderator and also as an abrasive. 



 


What is electroplating?


               Electroplating is a process of metal coating through electrolysis. Electrolysis is passing of an electric current through an electrolyte solution. In other words, it is the process to cover a metal with a thin coating of another metal either for protection against corrosion or for beautification of house hold items. The electroplating may also be used to impart certain other properties to a metal surface, such as hardness, wear resistance and anti-frictional, electrical, magnetic or optional properties. Do you know how metals are electroplated?



               Electroplating is done in large vats containing a solution of some suitable salt of the metal to be coated. Bars or plates of metal are used as anode, and are arranged inside the vats. This metal body, called the work piece, makes the cathode. When the electric current is passed through the solution, by connecting the positive terminal of the battery to the anode and negative terminal to the cathode, the metal ions from the solution go towards the cathode and get deposited on the work piece and form a thin layer of metal on it. The metal from the anode goes on dissolving in the solution and finally gets deposited on the work piece.



               To ensure an even deposit, the work piece may be slowly rotated inside the vat. The surface to the work piece must be clean and free from grease, dirt or oxide films. These days the metals that are electroplated include silver, gold, nickel, copper and chromium. For silver plating, double cyanides of potassium and silver are used. The silver plating is usually done on brass table-wares such as spoons, forks and other utensils. It is also done on ornaments. The gold baths also contain double cyanides of gold and potassium. This plating is also done on ornaments. The nickel plating baths involve double sulphates of nickel and ammonium. The copper bath contains a solution of copper sulphate with small quantities of sulphuric acid. The chromium plating is done by using the solutions of chromic acid and chromic sulphate with small quantities of chromium carbonate usually used on machine parts.


               The other metals which are electroplated commercially include cadmium, cobalt, platinum, rhodium, tin, zinc, etc. In certain cases two or more metals are plated simultaneously as alloy coatings, e.g. copper-zinc, copper-tin, lead-tin, lead-tin-copper, tin-nickel and nickel-cobalt.

How is sulphuric acid manufactured?


          Sulphuric acid is called the king of acids because of its importance as an industrial chemical. It is used in the manufacture of fertilizers, dyes, drugs, explosives, paints, synthetic fibres and detergents. It is also used in the manufacture of other acids such as hydrochloric acid and nitric acid. Different metals are pickled in sulphuric acid to clean them. It is also used in refining sugar and petroleum and to produce a vast range of chemicals. Do you know how this acid is manufactured?



          There are two methods used to manufacture sulphuric acid. One is known as Lead Chamber Process which dates back to about 200 years. The other is known as Contact Process. The former is less efficient and complex than the latter; still it is of considerable commercial importance. In Lead Chamber Process, first sulphur dioxide is obtained by burning sulphur or roasting pyrites. Then the sulphur dioxide thus obtained is oxidized by oxides of nitrogen to get sulphur trioxide which reacts with steam to produce sulphuric acid.



          Sulphuric acid is commercially manufactured by contact process. In this method the sulphur dioxide gas is mixed with air and heated with a catalyst. The catalyst is either the metal platinum or a compound called vanadium pentaoxide. The catalyst helps to quicken the reaction. The sulphur dioxide combines with the oxygen in the air to form sulphur trioxide. When sulphur trioxide is dissolved in water, it forms sulphuric acid.



          Pure sulphuric acid is a heavy, oily, colourless liquid. It is very reactive and attacks most of the metals to form salts called sulphates. It quickly absorbs water and is often used as a drying agent.



          While handling sulphuric acid, one should add sulphuric acid to water and not vice versa. If water is added to sulphuric acid, the heat produced causes water to boil. This makes the hot acid spit dangerously.