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Iron in Ancient India c7: Chapter IV. Matters of Chemical Interest Relating to Indian Iron

Iron in Ancient India c7

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Chapter IV. Matters of Chemical Interest Relating to Indian Iron

Analysis of Indian Iron

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All the specimens of iron described before have not been analysed. The Archaeological Department would do well to have them analysed and thus help chemists to properly understand the subject of metallurgy of iron in ancient India.

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A complete analysis of the iron of the Delhi pillar by Sir Robert Hadfield has been given on page 19, and the analysis of a specimen of Konarak iron by the author on page 26.

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Sir Robert Hadfield has published analyses of a number of specimens of Ceylonese iron of the fifth century A.D. in the Proceedings of the Royal Society and Journal of the Iron and Steel Institute.¹ As Ceylon might be regarded to be a part of Greater India in ancient times, analyses of Ceylon iron of the fifth century would be of interest in connection with Indian iron.² We give below the analyses of an iron nail, a chisel and a bill-hook.

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¹ Hadfield, *Journal of the Iron and Steel Institute*, 1912, pp. 163-168.

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² In the fifth century B.C. Vijaya, the son of Sinhabahu, a King of Magadha, is said to have been exiled by his father for many acts of fraud and violence, and this Prince came by sea to Ceylon, conquered the island and founded a dynasty of kings. Ceylon was converted into Buddhism in the third century B.C. by the missionaries sent by King Asoka under the leadership of his monk brother Mahendra who spent the rest of his life there.

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Iron nail :- Specific gravity 7.69.

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| | | | Per cent. |
| Carbon | .. | .. | Traces. |
| Silicon | .. | .. | .11 |
| Sulphur | .. | .. | Nil. |
| Phosphorus | .. | .. | .32 |
| Manganese | .. | .. | Nil. |

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Iron chisel :— Specific gravity 7·69. Carbon .. .. .. Traces. Silicon .. .. .. ·12 Sulphur .. .. .. ·003 Phosphorus .. .. .. ·28 Manganese .. .. .. Nil. Iron .. .. .. 99·3

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Iron bill-hook :— Specific gravity 7·5. Carbon .. .. .. Traces Silicon .. .. .. ·26 Suphur .. .. .. ·022 Phosphorus .. .. .. ·34 Manganese .. .. .. Traces.

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It will be noted that the composition of Ceylonese iron is exactly analogous to that of the iron of the Delhi pillar and Orissan beams. It is very likely that Indian iron was exported to Ceylon in ancient times.

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An analysis of a specimen of cast iron discovered in the ruins of Bhaba Chandra Pāt near Rungpur has been given in the paragraph dealing with cast iron (p. 78).

Tensile Strength of Indian Iron

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Mr. Monomohon Ganguli of the Public Works Department, whose recent work on " Orissa and her Remains " is an excellent publication on the subject, sent a very small piece of wrought iron from an iron beam at Bhubaneswar to the Civil Engineering College, Sibpur, where Prof. Sarat Kumar Dutt tested its tensile strength in the Testing laboratory of the College. Prof. Dutt got a small piece made of it of cross-section ·27" X ·415" and after testing it observed " this broke at 1·6 tons. The breaking strength accordingly comes to about 14·3 tons per square inch . . . . unfortunately the sample was not without flaws and the test piece broke at one of these flaws . . . . If it had been possible to obtain a decent sample of the iron, I believe, a strength of 20 tons per square inch could be easily attained," the accepted tensile stress of pure wrought iron having an average of 25 tons per square inch. "The assurance of Prof. Dutt that a decent sample of this iron could easily show a strength of 20 tons per square inch reflects great credit on the Orissan matallurgists of a bye-gone age, for the average tensile strength of wrought iron was 23 tons per square inch in England only 36 years ago."¹

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¹ Monomohon Ganguli's "Orissa and her Remains", p. 263.

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Prof. Dutt's experiments are, however, not very conclusive. Fortunately we have before ourselves the experiments of Sir Robert Hadfield on the tensile strength of Ceylonese iron, which are quite conclusive. Sir Robert found that the breaking load in the case of the iron nail was 21 tons per square inch, the chisel 26 tons, and bill-hook as high as 29 tons per square inch, being higher than the figure for wrought iron. This no doubt is owing to the considerable percentage of phosphorus present, which stiffens or hardens iron.

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Hadfield has also determined the Fremont shock test, the Brinell ball test for hardness, as well as scleroscope hardness of the specimens of Ceylonese iron. His conclusions are summarized thus: "The Fremont shock tests show fair results on the specimen taken from the chisel, namely 17 kilogrammes, with 85° bend. The other specimens, however, show much lower figures, namely the nail (1 kilogramme by only 1° bend) and the bill-hook (7 kilogrammes by 35° bend). The hardness by the Brinell method varied from 117 to 166, one result from the nail showing 209; but this is abnormal, and cannot be accepted as representative. The scleroscope tests varied from 25 to 44, and as a comparison it may be mentioned that water-quenched carbon steel by this latter method shows 100 and ordinary wrought iron about 20."

Micrographic Examination of Ancient Ceylon Iron

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The author is not aware of my micrographic examination of the iron of the Delhi pillar or any other specimen of ancient Indian iron. The results of micrographic examination of the three specimens of Ceylon iron by Sir Robert Hadfield will prove interesting. For photographs of micro-sections the reader is referred to Hadfield's paper. We give below only the results obtained by him with respect to the iron chisel, nail and bill-hook, analyses of which have already been given.

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*Iron chisel*: The transverse section shows that the chisel has been carburised, the section showing the carburised areas to be on two sides. The carburisation varies on two faces from saturation point (‘9 per cent) to about ‘2 per cent certain on the outside edge and the depth of carburisation from the edge inwards is also shown to be variable. The presence of matensite and hardenite suggest the important information that the chisel has been quenched. Further micro-sections were prepared from the specimen cut from the nose of the chisel. These photo-micrographs also appear to carry evidence that the chisel has been quenched for the structure is in parts martensitic. Troostite is certainly also present, which is probably the result of tempering by the long lapse of time. Hadfield believes that for the first time there has been put on record evidence of the art of cementation having been known 1500 to 2000 years ago, as shown by these specimens; probably, therefore, such knowledge could be traced back still further.

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*Iron nail*: The microstructures indicate a remarkable conglomeration. One plate shows a weld running diagonally across the section, and along the edges of the weld there are carburised areas. Another notable point is that on one side of the weld the slag shows the effect of the forging, whereas on the other side there is no such sign. The specimen is covered with slip bands and has evidently undergone severe hammering, probably in its use as a nail. The carbon in the carburised areas exists as granular pearlite.

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*Iron bill-hook*: The report of the microstructure of the specimen shows that it contains a large amount of slag and appears to represent what would be now termed a somewhat low quality of wrought iron. There seems to be practically no carbon present and therefore no evidence of treatment other than forging can be obtained.

Varieties of Indian Iron

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At present three principal varieties of iron are recognized according to the amount of carbon contained in them, viz, wrought iron, steel and cast iron. Each of these principal varieties is again sub-divided into other varieties according to the difference in their composition and properties. In ancient India also various kinds of iron were known and recognized by their different properties. The principal varieties were ‘munda’ (cast iron), ‘tikshna’ (sharp iron or steel) and ‘kānta’ (wrought iron).

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The Sanskrit work *Yuktikalpataru*, a manuscript of the eleventh century, which has not yet been published, describes the relative goodness of various qualities of iron thus: “*Crouncha* iron is twice better than *shāmānya* (ordinary) iron, *kālinga* (Orissan) iron eight times better than *crouncha* iron, *bhadra* iron one hundred times better than *kālinga* iron, *bajra* iron thousand times better than *bhadra*, *pāndi* iron again hundred times better than *bajra*, *niranga* ten times better than *pāndi* and *kāntha* iron million times better than *niranga* iron.”¹

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¹ [The Sanskrit text is provided in the block quotation above.]

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*Rasaratna-Samuchchaya*, a work of the thirteenth century, mentions three kinds of iron, viz. *munda* (cast iron), *tikshna* (steel) and *kānta* (wrought iron).

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*Munda* again is of three varieties, viz. ‘*mridu*,’ *kuntha* and *kadāra*.

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That which easily melts, does not break and is glossy is *mridu*; that which expands with difficulty when struck with a hammer is known as *kuntha*; that which breaks when struck with a hammer and has a black fracture is *kadāra*.

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*Tikshna*: There are six varieties of it, viz. *khara*, *sāra*, *hrin-nāla*, *tārābatta*, *bājira*, and *kālalauha* (black metal). One variety is rough and free from hair-like lines and has a quicksilver-like fracture and breaks when bent. Another variety breaks with difficulty and presents a sharp edge.

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*Kānta*: There are five kinds of it, viz. *bhrāmaka*, *chumbaka*,

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सामान्याद्दिगुणं क्रौंचं कालिङ्गाष्टगुणस्ततः ।
कलिः शतगुणं भद्रं भद्राद्वज्रं सहस्रधा ॥
वज्रात् शतगुणं पाण्डि निरणं दशभिर्गुणैः ।
ततः कोटिसमंवेत्त्यां कान्तालोहं मदारुणं ॥ युक्तिकल्पतरु ।

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This passage has been quoted in *Rasendrarshār-samgraha*, a Tāntrik work of the thirteenth or fourteenth century, thus showing that *Yuktikalpataru* must have been written two or three centuries before, so that its date would be circa eleventh century.

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The mention of *kalinga* iron in the passage quoted above shows that Orissa was always famous for her iron, and in fact even the Tata Iron and Steel Company get their supply of iron ores from the state of Maurbhanja in Orissa.

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*karshaka*, *drāvaka* and *romakāntā*. It possesses one, two, three, four and five faces and often many faces and is of yellow, black and red colour respectively. The variety which makes all kinds of iron move about is called *bhrāmaka*, that which kisses iron is called *chumbaka*, that which attracts iron is called *karshaka*, that which at once melts the iron is called *drāvaka* (lit. a solvent) and the fifth kind is that which, when broken, shoots forth hair-like filaments.¹

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From the description of the different varieties of iron it is quite evident that *munda* really means 'cast-iron' as its different varieties easily melt, break when struck with a hammer and have black fracture. The six varieties of *tikshna* are evidently varieties of steel presenting a 'sharp edge,' 'breaking when bent' or 'breaking with difficulty.' The five varieties of *kānta* are not easy to

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¹ अथातः,—
मुण्डं तीक्ष्णं च कान्तं च त्रिपकारमयः कृतम् । 70
अथ मुण्डम्,—
मृदु कृष्णं कदारं च त्रिविधं मुण्डमुच्यते ।
द्रवामविस्फोटं चिक्कणं मृदु तच्चमम् ॥
यत् यत् प्रसरेद् धातु तत्कृष्णं मध्यमं स्मृतम् ।
ख्यातं भज्यते भङ्गे ख्यां स्यात् तत् कदारकम् ॥ 71—72
अथ तीक्ष्णम्—
खरं सारं च हृल्लासं तारासं च वाजिरम् ।
काललोहाभिधानं च षड्विधं तीक्ष्णमुच्यते ॥ 75
पदयं पादगोक्ताभं भद्रे पारदवच्चपि ।
नमने भङ्गुरं यत् तत् खरतीक्ष्णदाहृतम् ॥ 76
वेजभं मुण्डधारं यत् सारलालं तदीरितम् ॥ 77
अथ कान्तम्,—
भ्रामकं चुम्बकं चैव कर्षकं द्रावकं तथा ।
एवं चतुर्विधं कान्तं रोमकान्तं च पञ्चमम् ॥ 84
एकद्विचतुःपञ्च सम्मुखं मुखमेव यत् ।
पीतं कृष्णं तथा रक्तं चित्रं स्यात् पृथक् पृथक् ॥ 85
भ्रामयेत्कोचजातं तु तत् कान्तं भ्रामकं मतम् ॥ 88
चुम्बयेच्चुम्बकं कल्पं कर्षयेत् कर्षकं तथा ।
साक्षाद् यद् द्रावयेल्लोहं तत्साम्यं द्रावकं भवेत् ॥ 89
तद् रोमकान्तं स्फुटिताद् यतो रोमोद्भवो भवेत् ॥ 90
रसरत्नसमुच्चय (Poona edition), fifth chapter, pp. 26 and 27.
The English translation of the passages is taken (with alterations) from P. C. Ray's History of Hindu Chemistry, Vol. I.

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identify. As *kānta* iron has been described the best of all varieties of iron in many books, it certainly refers to wrought iron, but in the passage quoted the varieties of *kānta* iron include magnetised iron also as they 'kiss' or 'attract' iron.

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In *Rasendrashār-samgraha* we have got a passage in which the same three kinds of iron are mentioned, viz. *munda*, *tikshna* and *kānta*. In this passage also it is stated that " *munda* is ten times better than iron rust, *tikshna* hundred times better than *munda*, and *kānta* million times better than *tikshna* iron." ¹

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¹ "किट्टात्मुण्डं मुण्डात्तीक्ष्णं ततोऽप्यधिकम् । तीक्ष्णात्कान्तं कान्तं" — रसेंद्रसारसंग्रह ।

Theory of Forging Iron Beams and Pillars

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It has already been stated that Dr. Percy, Dr. Murray and Sir Robert Hadfield found the Delhi pillar to be made of wrought iron. The iron beams of Orissa have also been found to be made of the same species of iron. These beams and pillars must then have been constructed by forging large quantities of wrought iron. The question now is—have these beams and pillars been forged as single columns or that short pieces of wrought iron have been forged and then welded? Experts are unanimously of opinion that such an enormous mass of iron as the Delhi pillar can even in these days of steam-rollers and hammers be with very grea difficulty forged. The conclusion therefore naturally arises that these beams and pillars must have been constructed by welding short pieces of wrought iron and not as entire columns. Direct evidence on this point is forthcoming, though it still reflects the greatest credit on the old Hindu metallurgists who could have successfully carried on the welding operations so very skilfully as to be scarcely perceptible.

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Writing about the beams in Konarak, H. G. Graves points out: ² "One beam, which is now lying on the portico, has evidently been partially exposed for a long period to the sandy winds, for it is worn down at least an inch in depth, enabling the defective structure to be seen. This particular beam and the fractured ends show very clearly that the method of manufacture was by welding up small blooms, generally about 3 or 4 lbs. in weight. The blooms are commonly 2 by 1 inch in section, but occasionally 2 by 2 inches or 1 by 1 inch, and a common length is about 6 inches. In a few cases the blooms may have been larger or the welding was done more effectively. The rough sketches appended to this paper show with fair accuracy the relative sizes and disposition of the blooms in several beams. Many of the broken ends show the existence of irregular and sometimes uniform cavities. It is possible to thrust a stick down some of them to a depth of 7 or 8 feet, and the sand-blasted specimen shows a cavity nearly the whole length of the beam. From these hollows, bits of cinder can be raked out." The blooms were probably welded together into short bars which were then in turn welded into big beams. Mr. Graves say that externally the beams are well finished though the cracks and lines show where joints were (see plate No. 4).

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² Journal of the Iron and Steel Institute, 1912, No. 1, Vol. 85, p. 196.

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As regards the Delhi pillar, the forging in this case is much more perfect than that of the Orissan beams and hence difficult to detect. The Committee of the Iron and Steel Institute in 1872, however, made some special enquiries with regard to this pillar.¹ Lieutenant Spratt of the Royal Engineers, then stationed at Delhi, came to the conclusion after enquiry that "the iron of which the pillar is made seems to have been originally in blooms of about 80 lbs. weight each." Even as early as 1858 Mr. Charles Wood of Middlesburgh, who was in India at the time of the Mutiny, stated that he believed that the pillar was of wrought iron and that it had been made by welding small pieces into the end of a shaft or bar. In 1871 Mr. Robert Mallet had stated: "We are thus obliged to consider that this pillar is not a casting but a huge forging in .... wrought iron," while shortly afterwards Mr. G. M. Fraser contributed a long letter to the *Engineer*, Vol. xxxiii, pp. 19, 20, in which the fact is clearly expreseed that the pillar was made of malleable iron and produced by welding together successive lumps or *mootees* of wrought iron which had been produced in a primitive blast-furnace. Fergusson, Vincent Smith, Ganguli and others agree in subscribing to this theory. This theory receives an added confirmation from the existence of many holes at irregular intervals in the Dhar pillar into which crowbars have evidently been put in order to help welding. Though at first sight the almost perfect finish of the exterior, specially of the Delhi pillar, negatives the hypothesis of forging small pieces into one whole, but when we judge of the almost unsurmountable practical difficulties of forging an *entire* piece of wrought iron as the Delhi or Dhar pillar appears to be, the author, at any rate, cannot but subscribe to the view that the method of forging the Delhi, Dhar, and Mount Abu pillars, as well as the gigantic Orissan beams, is unmistakably the same, viz. the method of welding short pieces into entire pillars and beams.

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¹ Ibid., 1872, Vol. II, p. 156.

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EXPLANATION OF "CORROSION RESISTANCE" POWER OF INDIAN IRON.

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(a) *Low manganese with low sulphur and high phosphorus.*

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Surprise has not unreasonably been expressed at the fact that the iron pillar at Delhi and other ancient specimens of iron have not rusted in a marked degree. General Cunningham offered a curious explanation of this fact by supposing that the oil of the bodies of the pilgrims who visit the Delhi pillar and embrace it as a mark of merit keeps it immune from rusting, but the learned General does not seem to have explained how the capital of the pillar, which is too high for human embrace, could be preserved in the way it has been preserved. The Delhi pillar is the best preserved of all the pillars. Mr. Graves points out that some of the Konarak beams were so heavily rusted that flakes half a foot square and half an inch thick could be scaled off. Most of them, however, were only superficially rusted and the rusting is mainly due to the beams remaining underground for two or more centuries. The iron clamps found at Bodh-Gaya are also very heavily rusted. The specimens of Singalese iron examined by Sir Robert Hadfield were well preserved, though belonging to the fifth century A.D. Dr. A. S. Cushman¹ is disposed to be philosophically inclined when he says, and says perhaps rightly, that "chemical and physical examinations of such ancient specimens might point the way to practical improvement in our own age, for one criticism that was often passed on modern steels was that their tendency to corrode and disintegrate stood in direct ratio to the rapidity with which they were manufactured ....... It seems to be a law of Nature that her materials should respond to the manipulations of the hands of man, and acquire properties that machinery cannot give." Be that as it may, two explanations are possible of this remarkable power of ancient specimens of iron of resisting corrosion—either there was something in the composition of the iron or that the beams were painted, or both. To the author it appears that both the factors have operated in enabling the Indian iron pillars and beams to withstand the corroding influence of wind and rain. In the first place the one point remarkable regarding the composition of the Delhi iron, Singhalese iron and other specimens of ancient iron is that all these specimens of iron are *free* from manganese and sulphur and contain a *tolerably high percentage of phosphorus*. The author agrees with Dr. Cushman when he suggests that probably "low manganese with low sulphur and high phosphorus would lead to high corrosion resistance" in iron.

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¹ Ibid., 1812, No. 1, p. 177.

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Dr. Cushman gives an analysis of an iron nail made in Virginia more than one hundred years ago. It was remarkably well preserved and contained, like old Indian iron, "low manganese with low sulphur and high phosphorus." The analysis was as follows:—

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| | Per cent. |
| Sulphur | ·013 |
| Manganese | ·06 |
| Carbon | ·03 |
| Phosphorus | ·205 |
| Silicon | ·121 |
| Copper | ·027 |
| Oxygen | ·15 |

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Professor Henri Le Chatelier was also struck by the almost complete absence, both of manganese and of carbon, which always occurred in noteworthy proportions in steels made by melting processes and also by the relatively high percentage of phosphorus. He also suggested that it was perhaps to the concurrence of these three factors that the exceptional durability of ancient Hindoo irons was to be attributed.¹

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¹ Journal of the Iron and Steel Institute 1912, p. 180.

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The author, however, is not aware of any experiments undertaken to confirm this theory and would take this opportunity of inviting chemists interested in the question of corrosion of iron to make further experiments on the subject.

(b) Application of paints on iron beams and pillars

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Besides the question of the composition of Indian iron the author has a suspicion in his mind that the pillars and beams were originally *painted*. Direct evidence on this point is also forthcoming, as Abul Fazal in the 16th century saw the beams at Puri painted.² The peculiar colour of the iron, specially at the top portion of the Delhi pillar, which misled early observers into thinking that the pillar was made of copper or bronze, might have been due to some kind of paint used for painting the pillar. The author has found out two formulæ of such paints used for hardening as well as preserving iron instruments in *Sārangadhar Padhati*, a compendium on miscellaneous subjects of the 14th century by the alchemist Sārangdhar. The first formula is briefly the following: "Grind together *pippali* (piper longum), rock salt and *kushta* wood (costus speciosus or saussurea Lappa) in cow's urine and cover the iron instrument with the mixture thus obtained. On now heating the instrument in the fire and then quenching in oil the instrument will be of superior quality."³ The second formula runs thus: "Grind together the five kinds of salt, mustard and honey and after painting the instrument with the mixture heat in the fire until at "yellow heat" its colour becomes blue like that of the throat of a peacock. The instrument would, on quenching in cold water, be quite good."⁴ Such an instrument will become extremely hard, so much so that "it will penetrate through the hardest armour as if through leaves of trees."¹ These two formulæ bring out two facts of importance. In the first place it is known as an undoubted fact that in the 14th century at any rate the Hindus were quite familiar with the process of hardening iron by quenching hot iron either in oil or water, and in the second place iron, at least iron instruments, were painted with a mixture containing salt and other ingredients and then heated in the furnace. The exact chemical action that takes place is difficult to understand. At first chlorides of iron are produced which perhaps on heating decompose, leaving a coating of the oxides of iron. It is possible that the Delhi and other pillars and beams were painted with a similar mixture and then heated in the fire, the process being continued, possibly with alterations, from early times down to the fourteenth century.

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² Ganguli's *Orissa and her Remains*, p. 262.

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³ पिप्पलीवेच्यो कुष्ठं गोमूत्रेण तु पेषयेत् ।

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⁴ अनेन लेपयेल्लोहं ततो चाग्नौ प्रतापयेत् । ततो निम्मज्जितं तेले लोहं तच्च विशिष्यते ॥ पञ्चभिर्लवणैः पिष्टं मधुभिस्तैः ससर्पपैः । रभिः प्रलेप्यल्लोहं ततो चाग्नौ प्रतापयेत् ॥

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¹ Annanda K. Kumarswami, Medieval Singhalese Art, p. 200.

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Dr. Kumarswami gives a somewhat different formula used for a long time in Ceylon and even now to give a 'blued' colour to iron articles and also to prevent rusting. The formula runs thus: "Take two parts of alum, one part of copperas, two parts of the leaves of *oxalis corniculata* and grind together and allow to stand three days; add the juice of one lime and spread over the iron to be coloured; place carefully in the fire until the right colour is attained."² Dr. Kumarswami explains the chemical action by supposing that "apparently the oxalic or other organic acid in the preparation reduces any higher oxide of iron to the ferrous state, and when applied to the steel and heated, slight etching takes place and a probable reduction of part of the sulphate to sulphide of iron. The temperature employed would affect the amount of reduction and oxidation. The blue colour is probably due to the uneven distribution of oxide and sulphide of iron."

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Moreover in the *Ayeen Akbari* we find that during the Moghul times iron guns when completed were painted with colour paints, and called 'rangin' (coloured).³

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³ Ayeen Akbari, Gladwin's Translation, Vol. I, p. 112.

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निक्षिप्यौषधं तत्रपोतं तस्योषधम् । ततस्तु विमलं तोयं पाययेच्छस्त्रमुत्तमम् । येन दुर्भेदशस्त्राणि भेद्येत्तु सबपर्वतम् ।

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COMPOUNDS OF IRON.

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(a) *Oxides of iron.*

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Of the compounds of iron the oxides of iron and the sulphide were artificially prepared and used in the Hindu system of medicine. The chloride of iron was also probably known but seldom used. The Buddhist alchemist Nāgārjuna (second century A.D.) is universally credited as the discoverer of the process of "killing" metals and specially iron. For example Chakrapāni (eleventh century) in describing the process of killing iron says: "I shall now describe the science of iron as promulgated by the sage Nāgārjuna." The author of *Rasendra-Chintāmani* also does the same.¹

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¹ नागाजुनो मुनीन्द्रः शशास मलोपशमनमित्यचनम् । तस्यानुकृतये वयंने तदिमदाचरैर्युमः ।

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The first notice of 'killing' iron and other metals (gold, silver, lead, copper and tin) occurs in the *Uttartantra* or supplement of the *Sushruta*, which is said by the commentator Dalhana to have been added by Nāgārjuna, who is also the redactor of *Sushruta*. In it we find the process called *ayashriti-bidhi* of iron and other metals in which "thin leaves of iron are to be smeared with the levigated powder of 'the salts' and heated in the fire of the cow-dung cakes and then plunged into a decoction of the myrobalans and assafœtida. This process is to be repeated sixteen times. The leaves are then to be ignited in the fire of the wood of *mimosa catechu* (khadira) and afterwards finely powdered and passed through linen of fine texture. The above process is equally applicable to the roasting of the other metals."²

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² तोच्छलोचपत्राणि तमुनि लवणवगेप्रदिग्धानि गोमय्याग्निप्रतप्तानि विफलाम्लसारा- दिकषायेध निष्वांपयेत् षोडशवारान् ततः खदिराङ्गारतप्तान्युपशम्यतप्तानि सूक्ष्मचूर्णानि कारयेत् । ...... एतेन सर्वलोहेषु अयस्कृतयो व्याख्याताः । सुश्रुत, चिकित्सास्थान ।

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Chakrapāni (eleventh century) gives an elaborate account of Nāgārjuna's process which may be summarised thus: "a bar of iron is to be rubbed with the levigated powder of the following vegetable products among others: the belleric myrobalans, *clitoria ternatea*, *vitis quadrangularis*, *boharhaavia diffusa* and *verbesina calend*. It is then strongly heated to the fusing point and plunged into the decoction of the myrobalans. The iron is then powdered by being beaten with an iron hammer. The powder is then digested in the decoction of the myrobalans and roasted repeatedly in a crucible.” *Rasendra-chintamani* (thirteenth century) gives the same account of Nāgārjuna’s recipie. *Rasendra-shār-samgraha* (fourteenth century) gives an elaborate account of the process of killing iron which is given below. *Kānta* (wrought) iron, being the best of all kinds of iron, has been recommended by all authorities as best suited for the purpose of “killing.” *Rasendra-shār-samgraha* writes:—

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When the proper kind of iron is selected, it is first finely powdered and then purified (शोधन) by macerating it in a decoction of the “three myrobalans” (त्रिफला). The iron is then again immersed in the same decoction and dried again in the sun. This process is to be repeated seven times. This is called “bhānu-pāka-bidhi” (भानुपाकविधि). The iron is next boiled in decoctions of various substances depending on the nature of the disease for which it is to be used. This process is called “sthāli-pāka-bidhi” (स्थालीपाकविधि). The iron thus treated is now washed in clear water and roasted inside two earthenware concave dishes with their mouths placed on each other and luted with mud. This pair of dishes is then put in a pit of suitable dimensions dug in the earth and heated by means of burning cowdung-cakes. This process is called “puta-pāka-bidhi” (पुटपाकविधि). The iron is then to be roasted ten, hundred or even thousand times, and it is believed that the greater number of “putas” iron has been subjected to, its medicinal efficacy increases in a corresponding degree. The alternate maceration and heating make the powder very light, and, in fact, the test prescribed by *Rasendra-shār-samgraha* by means of which the proper number of putas is to be judged is the extreme lightness of the powder. “The iron is to be roasted until being finely powdered and thrown on water, it will swim like a duck on account of its lightness.” 1

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It would interest readers to learn the methods of preparation

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वाजाकषाय विशेयः दशादिगतपाचकाः ।
तानदेव पुनस् तोयं यावच्चूर्णीकृतं कले ।
निस्तारन्ते जलेनैव समुत्तरति पंकवत् ॥

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of killed iron by modern Aurvedic physicians. As most Aurvedic physicians prepare their own medicines, the method of preparing the same medicine varies considerably. So far as we have been able to collect information, there are three different methods of preparing "lauhas."

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(1) Some physicians procure the best kind of iron, heat it in a blacksmith's forge and take the rust formed on the surface of the iron.

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(2) Others keep steel immersed in cow's urine for years together and take the rust collected on the surface.

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(3) While some are reported to prepare their "lauhas" by repeatedly heating powdered ferrous sulphate (क्षीरकास). Of course the method given in Chakrapāni, Rasendra-shār-samgraha and other works is followed by many orthodox physicians. In the methods Nos. (1) and (2) the rusts obtained are purified in the usual way, and then formed into balls with cow's urine or a decoction of the "three myrobalans," dried in the sun and calcined in the pit by means of burning cow-dung cakes in the usual way. The balling, powdering and calcining in an enclosed space are repeated ten, hundred or thousand times.

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We collected "lauhas" which have undergone different number of "putas" for analysis. The colour of these samples varied from greyish black and grey to orange-red. It was observed that one "puta lauha" was greatly attracted by a magnet, "lauha" which has been calcined ten times was attracted to a less degree, while a sample of seventy-eight "puta lauha" was very slightly attracted. As regards iron which has been calcined hundred or thousand times, it was not in the least attracted by a magnet.

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Qualitative analysis¹ showed the presence of a small quantity of soluble salt mostly potassium phosphate, siliceous matter and iron. There was no carbon (as we expected), nor any aluminium. The "one-puta," "ten-puta" and "seventy-eight-puta" "lauhas" are the products of heating the same sample of iron. The "hundred-puta" and "thousand-puta" "lauhas," both marked (A), are again the oxidation products of another sample of iron. Lastly, the "thousand-puta" "lauha," marked (B), is a different preparation.

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¹ The process of "killing" iron and analysis of "killed" iron have been reproduced here from a paper by the author and Mr. Birendra Bhusan Adhicari, Journal of the Asiatic Society of Bengal, 1910, 385.

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| "One-puta lauha." | | "Ten-puta lauha." | |
| Fe (5 c.c. H. only) | = ·012 | Fe | = nil. |
| Feo | = 68·1 | Feo | = 23·1 |
| Fe₂O₃ | = 20·4 | Fe₂O₃ | = 40·0 |
| Siliceous matter | = 10·1 | Siliceous matter | = 32·1 |
| Soluble salt (mostly pot. phos.) | = 1·3 | Soluble salt | = 4·6 |
| | 99·912 | | 99·8 mm. |

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| "Seventy-eight puta lauha." | | "Hundred-puta lauha." (A) | |
| Fe | = nil. | Fe | = nil. |
| Feo | = 9·5 | Feo | = nil. |
| Fe₂O₃ | = 51·2 | Fe₂O₃ | = 83·9 |
| Siliceous matter | = 34·1 | Siliceous matter | = 12·7 |
| Soluble salt | = 5·4 | Soluble salt (of which P₂O₅=·9) | = 3·7 |
| | 100·2 | | 100·3 |

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| "Thousand-puta lauha." (A) | | "Thousand-puta lauha." (B) | |
| Fe | = nil. | Fe | = nil. |
| Feo | = nil. | Feo | = nil. |
| Fe₂O₃ | = 78·1 | Fe₂O₃ | = 84·9 |
| Siliceous matter | = 17·9 | Siliceous matter | = 11·3 |
| Soluble salt | = 4·1 | Soluble salt (of which P₂O₅=1·2) | = 3·8 |
| | 100·1 | | 99·7 |

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From the results of analysis given above it is clear that the magnetic properties of the samples of iron which have undergone a fewer number of "putas" are not due to free iron, which is present in minute quantities in the "one-puta" "lauha" but to ferroso-ferric oxides, the ferrous and ferric oxides being present in them in varying proportions.¹

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¹ Of Roscoe and Schorlemmer's " Treatise on Chemistry," Vol. II, Part 2, " Magnetic oxide of iron ";—" when iron is heated to redness in the air, it becomes coated with iron scale. This is a mixture or a compound of the monoxide and sesquioxide in varying proportions. The inner layer which is blackish grey, porous, brittle, and attracted by the magnet, has the composition 6 Feo Fe₂O₃ and is not magnetic. The outer layer contains a larger quantity of ferric oxide, is of a reddish colour and is more strongly attracted by the magnet than the inner portion."

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As the number of " putas " increases, the amount of ferrous oxide diminishes, and at hundred " putas," and above, the iron is wholly present in the form of ferric oxide. Hence " hundred-puta " and " thousand-puta " " lauhas " are not attracted by the magnet.

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2. Siliceous matter is present in very large proportion varying from 10·1 to as much as 34·1 per cent. This impurity comes, as was subsequently ascertained, from the stone plates (खल्ल) on which the iron is powdered many times.

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3. " Shata-puta," " Sahasra-puta," " lauhas " have almost identical composition. Both are impure ferric oxide, the percentage of which varies from 78·1 to 84·6. Both are non-magnetic and " swim like duck " on water. On account of the very large number of " putas " in the course of which it undergoes maceration, powdering and roasting for a thousand times, the " shahasra puta " " lauha " is lighter and finer than " shata-puta." The time taken to prepare these lauhas is very long indeed. If one " puta " be finished in one day, the preparation of " shata-puta " takes more than three months, and that of " shahasra-puta " about three years. As the roasting is carried on in closed vessels the oxidation proceeds very slowly. If, however, open vessels be employed in future the time may be greatly curtailed.

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4. The test of " swimming on water like a duck " is a crucial one with the Aurvedic physician for " lauhas." We have seen that precipitated ferric oxide of the laboratory does not " swim like a duck." It is probable that Aurvedic " lauhas," being very light and porous, are easily assimilated in the body while ordinary ferric oxide being not so light and porous is not easily taken up and hence not used by Allopathic doctors.

Sulphide of Iron

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The sulphide of iron does not seem to have been prepared in the pure state. It occurs in preparations such as *lauha-parpati*, *sidha-jogeswar* and other Tantrik medicines along with the sulphide of mercury and vegetable substances. The mixture of sulphides (lauha-parpati) is prepared, as described in Rasendra-shār-samgraha and other works, by taking two parts of mercury, two parts of sulphur and one part of killed iron and then melting this well-rubbed powder in an iron laddle with clarified butter on a gentle fire. It is then poured over plantain leaves and gently pressed and finally treated with vegetable substances.

Chlorides of Iron

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We have already referred to the *ayaskriti* of iron mentioned in the *Uttartantra* of the Shushruta in which iron is heated with the "salts" including common salt. A mixture of ferrous chloride and oxychloride and oxide of iron is probably formed in this reaction. The five kinds of salts are sauvarchala (probably nitre), saindhaba (rock salt), vit (a kind of common salt), audbhida (alkali carbonate) and sāmudra (sea-salt).

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