Chemistry in the Service of Mankind

Chemistry is defined as the science of atoms and molecules as it deals with the composition, structure and properties of matter which can be best described and understood in terms of these basic constituents of matter. Chemistry is the science not of the only about one hundred elements but of the infinite variety of molecules and related species that may be built from them.
Our body is made up of tissues, which are all composed of chemicals. We need an adequate supply of chemicals in the form of food, vitamins, hormones, and enzymes, which are all chemicals. For taking care of our health we need medicines. We find that chemicals and chemistry penetrate into every aspect of our lives as essential items of our daily needs such as: Paper, sugar, starch, vegetable oils, ghee, essential oils, tannery, distillery, soap, cosmetics, rubber, dyes, plastics, petroleum etc are all the valuable gifts of chemistry. The materials with which one comes into contact in everyday life are polymers, rubber, plastics, textiles and many of the constituents of living things, such as cellulose and proteins. Infact there is almost nothing that we use in our daily life and it is not a chemical. Hence study of chemistry is important atleast for the simple reason that besides being ourselves an assemblage of chemicals, we use many chemicals in almost all aspects of our daily lives.
The service of chemistry of medicine represents as one of the most fascinating facts of the story of the application of scientific knowledge to the welfare of mankind. These are substances which provide the necessary elements like Nitrogen, Phosphorus Potassium, and Calcium etc. to humans and plants. It is no longer a mystery for the informed farmers that the chief nitrogenous fertilizers are ammonium sulphate and Calcium ammonium Phosphate and. Super phosphates multiply the yield of crops many times.
While we are well posted with the hard fact that Arsenic and many of its compounds are deadly toxic, it is worth mentioning that Arsenic has also been used as a life saver. In the nineteenth century, physicians had no means of combating infection and patients usually had no fate but to die. The whole nature of medicine, however, changed in 1863, when French scientists, Bechamps, noticed that an arsenic compound was toxic to some micro-organisms whose report encouraged Paul Erhlich, a German scientist, to synthesize new arsenic compounds, testing each one for its organism killing ability and finally with his 606th compound of arsenic, Erhlich found a substance in 1909, that selectively killed the syphilis microorganism. At the time, syphilis was a feared and wide spread disease for which there was no cure; only suffering, dementia, and ultimately death were the obvious consequences. Erhlich’s arsenic compound, what he dubbed as a “Magic Bullet” provided miraculous cures, and a search for other chemical compounds that could be used in the treatment of diseases was launched.
In 1935, Gerhard Domagk, administered a dose of a dye called prontosil (that inhibits the growth of streptococci bacteria) to cure his daughter’s fever. This not only laid the foundation for modern chemotherapy but also grabbed a Nobel Prize for medicine for Domagk in 1939. This field, now known as Chemotherapy has produced one of the most effective tools of controlling bacterial infections and those of many other micro-organisms. Chemotherapy also provides one of the lines of attack against cancerous tissues. And it all started with an arsenic compound. In chemotherapy which is as indispensable and desirable now for cancer patients, many of whom have no hopes and options but to count the remaining days of their lives, as Radiation therapy, chemicals or drugs are used to selectively destroy infectious micro-organisms without destroying the live tissues or the host, though both chemotherapy as well as radiation therapy carry harsh side effects too. Ernest Fourneau, a French scientist in 1936 proved that in the human body, prontosil breaks down to give sulphanilamide. Sulphanilamide is the actual active agent that inhibits streptococci. This study led to the discovery of sulpha drugs and from there on growth of chemotherapy has reached amazing heights.
Analgesics such as morphine, codeine and heroin are mainly opium and its products that are effective analgesics but cause addictions too. Moreover their over- dosage can cause sleep and unconsciousness. Tranquillizers which reduce anxiety and tension being either sedatives or antidepressants (mood elevators) are also chemicals. Similarly sterilization, the process of complete elimination of micro-organisms includes chemicals that are known as antiseptics and disinfectants. It is a matter of immense pleasure and great satisfaction that now it has become not only widely known but has also been generally accepted atleast by a sizeable majority of sensible masses that with global population growing less by the days and more by the nights, birth control has become essential. Fortunately, there are drugs that control ovulation and if regularly consumed, function as effective contraceptives.
It has been established that Tension and Mental stress escalate the level of acid in bile juice causing hyperacidity that can be combated using antacids mostly bases like calcium carbonate, magnesium hydroxide or aluminium hydroxide in the form of tablets or aqueous suspensions. These react with hydrochloric acid in the stomach and neutralize it partially and bring relief to the sufferers from consequences of hyperacidity.
Histamine is naturally present in almost all body tissues and is released when the human body meets substances that cause allergies. For example, when a person is suffering from hay fever, histamine is released. Antihistamines that are used as drugs to control the allergy caused by histamines are nothing more than the chemicals, known as amines. It is worth noting that Alexander Fleming in 1920 found that bacteria do not flourish in nutrient agar surrounded by the fungus Penicillium notatum westling. He found that this fungus produces antibiotic called penicillin. Antibiotics are produced by micro-organisms that are toxic to other micro organisms.
We know that colored substances used for dyeing fabrics are called dyes. A true dye must have a suitable color; be able to attach itself to the material from solution or be capable of being fixed on it, and be fast to light and washing when fixed. For this it must be resistant to water, acid and alkali. Chromophores are unsaturated groups or groups with multiple bonds that impart color to the organic compounds. Examples are the nitro, the nitroso and the azo groups. Auxochromes (salt forming groups like hydroxyl, and amino) do not impart color to the chromogens in the absence of chromophores. However, when the chromogen has a chormophore, the auxochrome deepens the color of the chromogen.
Substantive dyes can be directly applied by immersing the cloth in a hot solution of the dye in water. They can be again classified into acidic and basic dyes. Acid dyes are sodium salts of sulphonic acid and nitro phenols. They are used for dyeing animal fibers (wool and silk) but not vegetable fibers (cotton). The dye solution is acidified with sulphuric or acetic acid. Basic dyes are generally salts of hydrochloric acid and colored bases. They can directly dye animal fibers but need a fixing agent called mordant (tannin) to dye vegetable fibers. These are used for dyeing silk and cotton. Methyl orange, an azodyes, is prepared by coupling diazotized sulphanilic acid with dimethylaniline. Aniline Yellow is another azodye but has little value as a dye because of its sensitivity to acids. This is the simplest basic azo dye and can be obtained by coupling benzene diazomium chloride with aniline. Malachite belongs to the triphenyl methane dyes, prepared by condensing 1 molecule of benzaldehyde with 2 molecules of dimethylaniline in presence of concentrated Sulphuric acid, H2SO4. Dyes can also be classified as natural and synthetic dyes. Compounds extracted from plants are called natural dyes. These were used in olden days to color fabrics. Alizarin (red) and indigo (blue) are two examples. Synthetic dyes came into being to provide more varieties of colors.
It needs no mention that there are many chemicals which find great use in cosmetics too. Creams like cleansing creams, cold creams, bleaching and vanishing creams are prepared synthetically from chemicals. Perfumes, talcum powders and deodorants are also some other cosmetic substances that are obtained from chemicals. Lipsticks, nail polish and hair dyes also are chemical substances. Perfumes have pleasant smell due to the esters used in their synthesis.
We also know that carbon fibers are made of long chains of carbon atoms. They are got from synthetic or regenerated fibers by heating them in the absence of oxygen. These fibers on heating decompose to produce carbon fibers. Besides being useful, chemicals find use in artifacts as well. Ceramics, paints, varnishes, glass, cement and likes are various other useful substances that contain various chemicals as their main components. Construction industry is the major beneficiary of such substances.
A passing reference may be given about the fact that micro alloyed steels that are tougher than higher alloys are intermediate carbon steel alloys with 0.3 to 0.6% carbon content. They also include vanadium, niobium (columbium), and titanium and so on. Their enhanced strength is due to the precipitation-hardening reaction where nitrides or carbonitrides are formed in steel. Therefore, nitrogen level control is a key factor for their strength.
It may not be exaggeration to say that whereas we are used to talk of chemicals in food, in actuality, natural food substances are various forms of chemicals. For example, rice is a carbohydrate. Fruits contain carbohydrates and organic acids like citric, benzoic, malic, and ascorbic acids. Vegetables contain proteins (amino acid blocks) and vitamins. Besides these, chemicals are used as preservatives too for canned or bottled food items. Preservatives are chemicals that are added to food materials to prevent the growth of micro organisms or prevent spoilage and increase their shelf life. Chemicals also find use as edible colors and artificial sweetening agents. Since sugar cannot be used as a sweetening agent for diabetic patients, artificial sweetening agents that are non-nutritive in nature are used as substituents for sugar (especially in soft drinks). Examples are saccharin which is 500 times sweeter than sucrose, and cyclamates. Food colors are used in ice creams, dairy products, sweet meat, soft drinks, confectionery, etc. These colors are also used in oral medicines like capsules, tablets, syrups and liquids to improve their appearance. Some of the primary colors are water soluble.
A common problems of the daily routine in homes and laboratory is that of removal of unwanted materials like oils, grease dirt, etc. from the surface of clothes, utensils, apparatus, machines and our skin. Soaps and detergents are best chemical used for this purpose. It may not be known to many of us that soaps are sodium or potassium salts of higher fatty acids like stearic, palmitic and oleic acids. Fatty acids are organic acids that have more than sixteen carbon atoms in their molecular structure. The sodium soaps are called hard soaps and the potassium soaps are known as soft soaps. Soaps are obtained from oils and fats. For example, tristearin is got from beef and mutton tallow, tripalmitin from palm oil and triolein from lard (pig fat), olive oil and cotton seed oil. In India, soap is commonly got from Coconut, groundnut, Til and Mahua oils. They possess the desirable properties of ordinary soaps and can be used with hard water and in acidic solutions as well. Synthetic detergents are sodium salts of long chain benzene sulphonic acids or sodium salt of long chain alkyl hydrogen sulphates. Their calcium or magnesium salts are soluble in water.
Finally it may not be out of context to add that propellants, insect-repellants and pheromones, are also chemicals. Propellants are the fuels such as alcohol, liquid hydrogen, liquid ammonia, kerosene, hydrazine and paraffin etc that are used in rockets for propulsion. Chemicals like dimethyl phthalate, N, N-diethyl- meta- toulamide, N – N – diethyl benzamide are used as effective repellents against mosquitoes, flies and other insects. These are widely used in insect repellant body creams. Another way to get rid of insects is to use pheromones or insect sex attractants. Chemicals used as Pheromones help induce the mating urge and attract insects of opposite sex. When coated on poisonous baits, they prove fatal for insects.