Category Chemistry

What is the Nitrogen Cycle?

          Our atmosphere contains about 78% of nitrogen. A certain amount of this nitrogen is constantly being removed, and an approximately equal amount is being returned. This continuous circulation of nitrogen among the soil, water, air and living organisms is known as the Nitrogen cycle. Let us see how the percentage of nitrogen in the air remains constant.

          All living things need nitrogen. It is part of proteins and nucleic acids, both of which are vital for life. How nitrogen is removed from atmosphere and again returned to the atmosphere is given below.

          A part of the atmospheric nitrogen is removed from the air by lightning. The sudden discharge of electricity causes some of the nitrogen and oxygen components in the air to combine, forming the oxides of nitrogen. When these nitrogen oxides are dissolved in water, they combine with other elements to form nitrogenous compounds.

          Some nitrogen is removed, from the air by certain bacteria and algae in a process called nitrogen fixation. Symbiotic bacteria present in the nodules of roots of some plants, such as peas, beans, gram etc. take up atmospheric nitrogen directly, and pass it on to the plants. Plants take up nitrogen compounds and convert them into proteins. These proteins are assimilated by animals. Some other plants, like rice, have symbiotic blue-green algae which fix atmospheric nitrogen.

          As a result of death, decay and excretion by plants and animals, the organic matter is converted into ammonium salts in the soil. Special nitrifying bacteria convert ammonia into nitrogenous compounds that are used up by plants. Animals get their nitrogenous compounds by eating plants, or other animals that eat plants.

          Thus an approximately equal amount of nitrogen is also being constantly returned to the atmosphere. Denitrifying bacteria change some of the nitrogenous compounds in the soil, back into gaseous form of nitrogen. These gases then return to the air.

          Thus nitrogen from the atmosphere passes into the soil, plants and animals and finally returns to the air. It may take thousands or millions of years, but every molecule of nitrogen eventually returns to the air.

 

What are proteins?

          Proteins are very important chemical compounds contained by all plants and animals. Probably life would not exist without proteins.

          The word ‘protein’ originated from a Greek word which means ‘first’, because proteins are considered to be the most essential part of the living matter. These chemical compounds are made up of chains of amino acids. There are more than 21 amino acids. Each amino acid has carbon, nitrogen, oxygen and hydrogen as its constituents. The different amino acids combine in different ways to form thousands of proteins.

            Proteins work in many different ways in the body. An important group of proteins, called enzymes act as catalysts in many biochemical reactions. Enzymes are essential for metabolic activity of the body. Some hormones, such as insulin, are also proteins. They are called regulatory proteins because they regulate blood pressure and blood glucose level. Immune proteins protect the body against infection. Transport proteins such as haemoglobin carry vital substances to different parts of the body. Movement of the muscles is helped by proteins called contractive proteins. Thus proteins are vital for the body. 

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What is a litmus paper?

          Litmus is used in chemistry to detect the presence of alkalis and acids. Litmus is a dye made from small plants called lichens. It is either red or blue in colour and is used in the form of a solution which is sometimes on a test paper.

          When lichen called Rocella Tincotoria is allowed to react with ammonia, potassium carbonate or lime, it gives a blue colour material. The paper is dipped into it and dried. This is known as a blue litmus paper, and is used to test acids. Acids turn blue litmus red.

          Orchil or cudbear is a red dye obtained from another species of lichens. This is used to make red litmus paper. Alkannet or alkanna is another dye obtained from the root of the plant Alkanna Tinotoria. The colouring ingredient, alkannin, is soluble in alcohol, benzene and others. When white paper is impregnated with an alcoholic solution of alkannet, it becomes red. This red paper is turned blue or deep violet by alkalis. 

          Neutral solutions (neither acid nor base) do not change the colour of litmus.

          When a chemist wishes to neutralize an acid solution, he first adds litmus solution. This changes its colour to red. The base is then added, until its colour changes to violet. The solution then becomes neutral, i.e. neither base nor acid and one more drop of base turns the solution blue.

          When acids and bases react, they produce salts by neutralization. For instance, the common salt that we use in our food is produced by the reaction of caustic soda and hydrochloric acid.

          Nowadays, litmus paper is made from several substances such as azolitmin, crysthrolitmin, spaniolitmin etc. These are apparently mixtures of closely-related compounds that were identified in 1961 as derivatives of the heterocyclic compound phenoxazine.

 

When were anaesthetics first used in operations?

          Before the discovery of anaesthetics, an operation used to be an agonizing experience for the patient. Even though different agents like herbs, gases, oils and drugs were used for relieving pain, the patient sometimes died from pain and shock. It was only with the discovery of modern anaesthetics that a major break-through was achieved in the field of surgery.

          An anaesthetic is a substance that causes a loss of sensation or feeling in the body. The history of its discovery is very interesting. In 1799, the British chemist, Sir Humphry Davy inhaled some ‘laughing gas’ (nitrous oxide) and found that it produced unconsciousness. Davy published this experience and in 1844 in the United States Horace Wells performed the first dental operation using nitrous oxide as an anaesthetic. Two years earlier, i.e. in 1842, the first painless operation had been carried out by Craw Ford W. Long, using ether as an anaesthetic. In 1847, chloroform was reported to have similar anaesthetic effect. At last surgeons had found a method of overcoming pain to carry out lengthy operations without undue haste. 

          Today, many new types of anaesthetics have been developed. Their application is of two types: local and general. Local anaesthetics are used to numb a particular part of the body. They act by blocking the transmission of electrical impulses along nerve cells, and are usually injected around the nerves that normally carry impulses from the area to be operated upon. The first of these anaesthetics was cocaine. This was superseded by another drug called procaine in 1905. Numerous drugs related to procaine such as lignocaine are nowadays used.

            General anaesthetics render the entire body unconscious. Nitrous oxide, ether and chloroform are included in this category, together with a more recently developed drug, halothane. Once inhaled, they act within seconds but recovery starts immediately after the drug is withdrawn. Halothane has been found to have side effects on liver. Now it has been replaced by ethrane.

          Under general anaesthesia, the patient’s respiration may be controlled externally. There are two reasons for this. First, general anaesthesia depresses the area of the brain that controls respiration. Second, for many operations the patient’s muscles need to be released which is achieved by giving a drug called curare.

          A person called an anaesthetist is trained to give proper amounts of anaesthetic to patients being operated for different ailments. At least one anaesthetist is always present in the operation room during the surgery.

 

What is the Theory of Relativity?

In the early nineteenth century people believed that light travelled through imaginary stationary medium called ether. It was believed that ether filled all space, and all movements could be measured absolutely with respect to it. It was also thought that the speed of light relative to a moving observer could be calculated in the same way as the relative speeds of any two moving objects. For example, just imagine two cars in the same direction: one going at a speed of 110 km/hr and the other at 80 km/hr. Passengers in the slower car would observe that the faster car is travelling at 30 km/hr.

Two American scientists, Michaelson and Morley, experimentally tried to measure the speed of earth through ether in 1887. But their result did not confirm the existence of the hypothetical medium ether. Later the explanation of negative results was offered by Albert Einstein. According to him, nothing like ether exists in the universe and the concept of absolute motion is meaningless. He also said that the speed of light is constant, no matter how fast the observer is moving. No material body can travel faster than light.

On the basis of his conclusions, Einstein formulated the Special Theory of Relativity in 1905. He showed that physical quantities like mass, length and time are also not absolute. They change as the bodies move. If a body moves with a large velocity, its mass increases and it becomes shorter. 

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How is nylon made?

            Nylon is one of the most important chemical discoveries of the 20th century. It is one of the toughest, strongest and most elastic substances we have today. It is a synthetic plastic material which is made from chemicals derived from coal, water, air, petroleum, agricultural by-products and natural gas.

            It was first developed by a research team headed by a U.S. chemist Wallace H. Carothers working in E.I. Dupant de Nemours & Co. He began experimenting with it in the 1920s. In 1935, he produced the first piece of nylon. It was converted into cloth in 1937.

            Nylon is made from two chemical compounds: Hexamethylenediamine and Adipic acid. Hexamethylenediamine consists of carbon, nitrogen and hydrogen. Adipic acid contains carbon, hydrogen and oxygen. Each of these substances contains six carbon atoms and the nylon produced by them has been named as Nylon-6, 6. Manufacturers combine the two compounds to form a substance called nylon salt. A solution of nylon salt is placed in an autoclave (a heating device). The autoclave heats the solution under pressure. Water is removed and the small molecules in the compound combine to form large molecules. This process is called polymerization.

            When caprolactam is used as the starting material, Nylon -6, 6 is obtained. It has been so named because it has six carbon atoms in the basic unit. It is comparatively a recent development.

            In some factories, the newly made nylon comes out of the machines as a plastic ribbon. This is then cooled, and cut into small pieces. Nylon fibres are made by forcing molten nylon through tiny holes in a device called spinneret. The thin streams of nylon that come out of the spinneret harden into filaments when they come in contact with air. Then they are wound into bobbins. From a single bobbin, as many as 2520 filaments are united into a textile nylon yarn. The fibres are drawn or stretched after they cool. The stretching action causes molecules in the fibre to fall into straight lines and make the fibres stronger and more elastic.

            Nylon can be formed into fibres, bristles, sheets, rods, tubes and coatings. It can also he rendered into powdered form for making moulds.

            Nylon fibres resist mildew and not harmed by most kinds of oil, grease and household cleaning fluids. It absorbs little water.

            Nylon is used to make many articles of clothing, parachutes, carpets, ropes, fishing lines and upholstery. It is also used in tyres and bristles in many types of brushes. Solid pieces of nylon are used to make bearings, gears and small machine parts. Unlike metal parts nylon bearings and machine parts need little lubrication.

            Recently a nylon derivative known as Qiana has been developed. It is a silk-like fibre used in clothing. Thus nylon has proved to be useful in many ways.