Iron pillar

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The iron pillar of Delhi, the capital city of India, is one of the world's foremost metallurgical curiosities, standing in the famous Qutb complex. The pillar—almost seven metres high and weighing more than six tonnes—was erected by Chandragupta II Vikramaditya^[1]. It is the only piece of the Hindu temple remaining, which stood there before being destroyed by Qutb-ud-din Aybak to build the Qutub Minar and Quwwat-ul-Islam mosque. Qutub built around it when he constructed the mosque.

The pillar is made up of 98% wrought iron of pure quality, and is a testament to the high level of skill achieved by ancient Indian iron smiths in the extraction and processing of iron. It has attracted the attention of archaeologists and metallurgists as it has withstood corrosion for the last 1600 years, despite harsh weather.

Contents 1 Description 2 Scientific analysis 3 See also 4 Notes 5 Further reading 6 External links

[edit] Description

The pillar, almost seven metres high and weighing more than six tonnes, was erected by Chandragupta II Vikramaditya (375 AD–414 AD), (interpretation based on careful analysis of archer type Gupta gold coins) of the Gupta dynasty that ruled northern India 320–540 ^[2]. The pillar with the idol of Chakra at the top was originally located at a place called Vishnupadagiri (meaning “hill with footprint of Vishnu”) ^[3]. This place has been identified as modern Udayagiri, situated in the close vicinity of Besnagar, Vidisha and Sanchi. These towns are located about 50 kilometres east of Bhopal, in central India. There are several aspects to the original erection site of the pillar at Udayagiri. It must be worth noting that Vishnupadagiri is located on the Tropic of Cancer and, therefore, was a centre of astronomical studies during the Gupta period. The Iron Pillar served an important astronomical function, when it was originally at Vishnupadagiri. The early morning shadow of the Iron Pillar fell in the direction of the foot of Anantasayain Vishnu (in one of the panels at Udayagiri) only in the time around summer solstice (June 21). The creation and development of the Udayagiri site appears to have been clearly guided by a highly developed astronomical knowledge. Therefore, the Udayagiri site, in general, and the Iron Pillar location in particular, provide firm evidence for the astronomical knowledge that existed in ancient India around 400 AD.

The pillar bears an inscription which states that it was erected as a standard in honour of the Hindu god, Vishnu. It also praises the valor and qualities of a king referred to simply as Chandra, who has been identified with the Gupta King Chandragupta II Vikramaditya (375-413). Made up of 98% wrought iron of pure quality, it is 23 feet 8 inches (7.21 m) high and has a diameter of 16 inches (0.41 m) at the bottom which tapers down on going up. The pillar was manufactured by forge welding and the temperatures required to form such of pillar by forge welding can be achieved by combustion of coal. The pillar is a testament to the high level of skill achieved by ancient Indian iron smiths in the extraction and processing of iron.

A fence was erected around the pillar in 1997 because people were damaging the pillar. There is a popular tradition that it was considered good luck if you could stand with your back to the pillar and make your hands meet behind it.

[edit] Scientific analysis

Metallurgists at IIT Kanpur have claimed that a thin layer of "misawite", a compound of iron, oxygen, and hydrogen, has protected the cast iron pillar from rust. According to them, the protective film took form within three years after erection of the pillar and has been growing ever so slowly since then. This information was wrongly flashed by the news media ^[4] based on an article that appeared in Current Science (see further). In the original article in Current Science, it has been mentioned that after 1,600 years, the film has grown just one-twentieth of a millimetre thick, according to R. Balasubramaniam of the IIT. In a report published in the journal Current Science^[5]], Balasubramaniam suggests that the protective film was formed catalytically by the presence of high amounts of phosphorus in the iron — this phosphorus is as much as one per cent against less than 0.05 per cent in today's iron. There are three stages identified in the protective passive film formation, as outlined in detail in the detailed article on the corrosion resistance of the Delhi Iron Pillar in Corrosion Science, one of the reputed journals in corrosion science and engineering ^[6] The high phosphorus content would be a result of the iron-making process practiced by ancient Indians, who reduced iron ore into iron with low carbon content by solid state reduction by employing charcoal as the reducing agent. Modern blast furnaces, on the other hand, use limestone in place of charcoal, yielding molten slag and pig iron that is later converted into steel. In the modern process most phosphorus is carried away by the slag. Since lime was not used in the ancient furnaces, a higher amount of phosphorus remains in the material ^[7][8].

Balasubramaniam states that the pillar is "a living testimony to the skill of metallurgists of ancient India". An interview with Balasubramaniam and his work can be seen in the recent article by Veazy ^[9].

Another theory suggests that the reason that the pillar resists rust is due to its thickness, which allows the sun to heat the pillar sufficiently during the day to evaporate all rain or dew from its surface. The accumulated heat also keeps the surface dry at night ^[10] For a detailed review of all theories proposed to explain the corrosion resistance of the Delhi Iron Pillar see the article in Corrosion Science by Balasubramaniam ^[11]

It was claimed in the 1920s that iron manufactured in Mirjati near Jamshedpur is similar to the iron of the Delhi pillar.^[12]. Further work on Advasi (tribal) iron by the National Metallurgical Laboratory in the 1960s did not verify this claim ^[13].

[edit] See also

• Ayas
• Wootz steel
• Dhar pillar
• Heliodorus pillar
• Wolfsegg Iron
• Nine Unknown Men

[edit] Notes

1. ^ Balasubramaniam, R. 2002
2. ^ Identity of Chandra and Vishnupadagiri of the Delhi Iron Pillar Inscription: Numismatic, Archaeological and Literary Evidence, R Balasubramaniam, Bulletin of Metals Museum, 32 (2000) 42–64.
3. ^ On the Astronomical Significance of the Delhi Iron Pillar, R Balasubramaniam and Meera I Dass, Current Science, volume 86 (2004) pp. 1134-1142. [1]
4. ^ Mystery of Delhi's Iron Pillar unraveled,Press Trust of India, Posted online: Thursday, July 18, 2002 at 1500 hours IST [2]
5. ^ On the Growth Kinetics of the Protective Passive Film of the Delhi Iron Pillar, R Balasubramaniam, Current Science, Volume 82 (2002) pp. 1357-1365. [3]
6. ^ On the Corrosion Resistance of the Delhi Iron Pillar, R. Balasubramaniam, Corrosion Science, Volume 42 (2000) pp. 2103-2129 [4]
7. ^ On the Origin of High Phosphorus Content in Ancient Indian Iron, Vikas Kumar and R. Balasubramaniam, International Journal of Metals, Materials and Processes, Volume 14 (2002) pp. 1-14
8. ^ For a detailed list of publications on Delhi Iron Pillar by Balasubramaniam, see [5]
9. ^ 1600 Years Young, Materials Performance, July, 2005. see also http://www.iupac.org/publications/ci/2005/2706/3_veazey.html
10. ^ B. Sanyal and R. Preston, Note on Delhi Pillar, Chemical Research Laboratory, London, 1952.
11. ^ [6]
12. ^ Andrew McWilliam 1920, cited in Chakrabarti 1992
13. ^ A.K. Lahiri, T. Banerjee and B.R. Nijhawan, “Some Observations on Corrosion-Resistance of Ancient Delhi Iron Pillar and Present-time Adivasi Iron Made by Primitive Methods,” NML Tech. J., 5 (1963) 46-5.

[edit] Further reading

• King Chandra and the Mehrauli Pillar, M.C. Joshi, S.K. Gupta and Shankar Goyal, Eds., Kusumanjali Publications, Meerut, 1989.
• The Rustless Wonder – A Study of the Iron Pillar at Delhi, T.R. Anantharaman, Vigyan Prakashan, New Delhi, 1996.
• Delhi Iron Pillar: New Insights. R. Balasubramaniam, Delhi: Aryan Books International and Shimla: Indian Institute of Advanced Studies, 2002, Hardbound, ISBN-81-7305-223-9. [7] [8]
• The Delhi Iron Pillar : Its Art, Metallurgy and Inscriptions, M.C. Joshi, S.K. Gupta and Shankar Goyal, Eds., Kusumanjali Publications, Meerut, 1996.
• The World Heritage Complex of the Qutub, R Balasubramaniam, Aryan Books International, New Delhi, 2005, Hardbound, ISBN 81-7305-293-X.
• Story of the Delhi Iron Pillar, R Balasubramaniam, Foundation Books, New Delhi, 2005, Paperback, ISBN-81-7596-278-X.
• Delhi Iron Pillar (in two parts), R. Balasubramaniam, IIM Metal News Volume 7, No. 2, April 2004, pp. 11-17. and IIM Metal News Volume 7, No. 3, June 2004, pp. 5-13. [9]
• New Insights on the 1600-Year Old Corrosion Resistant Delhi Iron Pillar, R. Balasubramaniam, Indian Journal of History of Science, 36 (2001) 1-49. [10]

• The Early use of Iron In India. Dilip K. Chakrabarti.1992. New Delhi: The Oxford University Press.

[edit] External links

• Detailed list of Publications on Delhi Iron Pillar by Balasubramaniam, IIT Kanpur
• Corrosion resistance of Delhi iron pillar
• Nondestructive evaluation of the Delhi iron pillar Current Science, Indian Academy of Sciences, Vol. 88, No. 12, 25 June 2005 (PDF)
• The Delhi Iron Pillar

Coordinates: 28°31′28.76″N, 77°11′6.25″E