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NCERT Class 11 Knowledge Traditions and Practices of India Chapter 8 Chemistry and Metallurgy in India
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Chemistry and Metallurgy in India
Chapter: 8
| EXERCISE |
1. Which materials were used to make the colour of inks?
Ans: The general ingredients are pigment, binder, and vehicle or carrier. The oldest writing inks developed before 2500 BC were suspensions of carbon, typically lampblack, in water stabilised with natural gum, gelatin, or egg albumen. In contrast, modern inks are far more complex.
2. How was the concept of atoms described in the early Indian philosophical system?
Ans: Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped. Differences in atomic shape and size determined the various properties of matter.
3. Justify that copper metallurgy in India has indigenous origin.
Ans: Copper metallurgy in India has strong evidence of indigenous origins, supported by several factors. Archaeological excavations at sites such as Harappa and Mohenjo-Daro, which date back to the Indus Valley Civilization, reveal a significant use of copper tools and ornaments, indicating advanced local smelting techniques. This technological continuity is evident in the transition from copper to bronze during the Chalcolithic period, suggesting that metallurgical skills developed organically over time rather than being imported. Ancient texts, including the Vedas, reference the use of metals, highlighting a long-standing tradition of metallurgy embedded in local practices. Furthermore, distinct regional methods of copper production, utilising local ores and traditional furnaces, demonstrate that these techniques were adapted to the Indian environment. The cultural significance of copper in various artefacts and rituals further emphasises its indigenous importance. Additionally, while trade contacts existed with other civilizations, there is minimal evidence to suggest that copper metallurgy was introduced from outside, reinforcing the notion of a self-sustained indigenous industry. Overall, the combination of archaeological findings, historical references, and cultural relevance strongly supports the view that copper metallurgy in India has deep indigenous roots.
4. What makes the extraction of zinc difficult? How did the Indian smelters carry out the process of smelting of zinc?
Ans: The extraction of zinc poses several challenges primarily due to its occurrence in nature as part of various complex ores, particularly zinc sulphide (sphalerite), which requires specific and often intricate processes to separate the metal. The low boiling point of zinc compared to other metals makes it volatile during extraction, leading to potential losses if not managed properly. Additionally, the presence of impurities in the ores can complicate the smelting process, requiring careful purification steps to achieve a high-quality product. In India, traditional smelting methods have been employed by smelters to extract zinc, typically involving roasting the zinc sulphide ore to convert it into zinc oxide. This oxide is then subjected to a reduction process, often using carbon in the form of coke, at high temperatures in a furnace. The smelting process may also involve the use of retorts to condense and recover zinc vapours, ensuring efficiency and minimising losses. Overall, the combination of geological, chemical, and operational factors makes zinc extraction a complex yet essential industrial process.
5. How can one show that the smelters and smiths of the Indian sub-continent had advanced knowledge of copper metallurgy?
Ans: The smelters and smiths of the Indian subcontinent demonstrated advanced knowledge of copper metallurgy through various historical and archaeological evidence. Excavations at ancient sites such as Harappa and Mohenjo-Daro reveal sophisticated techniques for copper extraction and alloying, including the production of high-quality bronze. Artefacts from these sites showcase intricate craftsmanship in the form of tools, weapons, and ornaments, indicating a deep understanding of metalworking. Moreover, ancient texts and inscriptions reference advanced metallurgical processes, such as the methods of smelting and casting. The presence of large furnaces and the use of controlled heating techniques further highlight their proficiency in manipulating metal properties. Additionally, the trade of copper and bronze artefacts across regions points to established networks and a strong understanding of metallurgy that facilitated knowledge exchange. Collectively, these aspects illustrate that the smelters and smiths of the Indian subcontinent possessed not only technical skills but also a rich tradition of metallurgy that contributed to their advanced capabilities.
6. What caused the decline of knowledge of metallurgical skills in India?
Ans: For over 7000 years, India has had a high tradition of metallurgical skills. The two important sources for the history of Indian metallurgy are archaeological excavations and literary evidence. The first evidence of metal in the Indian subcontinent comes from Mehrgarh in Baluchistan, where a small copper bead was dated to about 6000 B.C.E. It is, however, thought to be native copper, which has not been extracted from ore. Archaeological excavations have shown that Harappan metalsmiths obtained copper ore from Aravalli Hills, Baluchistan or beyond. Many bronze figurines of humans and animals have been unearthed from Harappan sites.
Systematic excavations at Mohenjodaro in Sindh and Harappa in Punjab show that during the mature Harappan period, the metal workers perfected the metallurgical skill. Harrapans used metals like tin, arsenic, lead, antimony, etc., for alloying. They had also perfected the wax technique of metal casting in as early as the third millennium B.C.E. They melted and forged a variety of objects from metals such as lead, silver, gold and copper. They improved the hardness of copper for making artefacts by using tin and arsenic.
7. Why has the iron pillar of Delhi not rusted even after exposure to moist air for so many years?
Ans: When iron ore is reduced by charcoal in solid state, it forms porous iron blocks. Therefore, reduced iron blocks are also called sponge iron blocks. Any useful product can only be obtained from this material after removing the porosity by hot forging. The iron so obtained is termed as wrought iron. The process control achieved by the ancient iron smelters was so high that they could produce 6–10 tons of wrought iron of almost uniform quality used for the manufacture of objects like the world famous Iron Pillar at Delhi.
the world famous Iron Pillar at Delhi. Engraved Sanskrit inscription suggests that it was brought here from elsewhere in the Gupta period. The average composition of the components present in the wrought iron of the pillar besides iron are 0.15% C, 0.05% Si, 0.05% Mn, 0.25% P, 0.005% Ni, 0.03% Cu and 0.02% N. The most significant aspect of pillar is that there is no sign of corrosion in spite of the fact that it has been exposed to the atmosphere for about 1,600 years. High purity of the metal (> 99 percent) and presence only of traces of injurious elements, and clean environment prevented it from rusting. Also most recently, Balasubramaniam has explained that a composite layer of iron hydrogen phosphate formed on the pillar prevents it from rusting. Rapid industrialisation and the increase in traffic in and around Delhi is raising the sulphurous gases in the environment. If this remains uncontrolled, corrosion may occur and weaken the matrix of the pillar. Another famous iron pillar is located at Mookambika temple in Kodachadri Hill in a town near Mangalore. It also belongs to the same period. The iron beams lying in the Surya temple at Konark are still bigger in size. Non corroding iron beams were being used extensively in the construction of temples in Orissa dating back to the sixth and thirteenth centuries C.E. Evidence of iron smelting are available in the NorthEast region also. Radiocarbon dating of charcoal from the iron slag obtained in this region provides evidence of continuous smelting in Khasi Hills. Meghalaya is the earliest iron smelting site studied in the entire region of North East India. The slag layer, which is dated to 2040±80 years BP (253 B.C.E. –A.D. 128) is the remnant of former iron ore excavation and iron manufacturing visible even now in the landscape of Khasi Hills.
