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Copper in Ancient India c11: Chapter VI. Compounds of Copper

Copper in Ancient India c11

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Chapter VI. Compounds of Copper

(a) Copper Sulphide

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Two compounds of copper were known in ancient India in the pure state—the sulphide and the sulphate.

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Of these the sulphide appears to have been first prepared artificially by Vrinda (circa 900 A.D.) under the name of *parpati-tāmram* in the following manner—“sulphur, copper and the pyrites are to be pounded together with mercury and subjected to roasting in a closed crucible.”[¹] The formula for this preparation, however, says Dr. Ray, does not occur in the Poona edition of Vrinda’s work but it is to be found in the Kashmir manuscripts under *Rasāyanādhicār*, so that the passage might be an interpollation. It is, however, certain that Chakrapāni (circa 1060 A.D.) prepared the compound in a pure state under the name of *tāmarajoga*. Chakrapāni writes “take a thin leaf of Nepalese copper and embed it in powdered sulphur. The substances are to be placed inside a saucer-shaped earthenware vesel and covered with another. The rims are luted with sugar or powdered rice-paste. The apparatus is heated in a sand-bath for three hours. The copper thus prepared is grounded and admixtured with other drugs.”[²] “Killed copper” mentioned in later alchemical works was prepared by first making copper amalgam by mixing copper with mercury and then heating the amalgam with excess of sulphur in a crucible when the mercuric sulphide sublimes off and the sulphide of copper is left behind. The roasting is repeated several times with sulphur in order to complete the conversion of copper into the sulphide.

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¹ Ray, History of Hindu Chemistry, Vol. 1. p. 32.

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² Ibid., p. 34.

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Copper sulphate works in Rajputana (Ball's Economic Geology of India).

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Indian blast furnace for smelting copper (Ball's Economic Geology of India).

(b) Copper Sulphate

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Blue vitriol of copper sulphate is designated in Sanskrit by the work *tutthwam* (तुत्थम्) from which the Persian word "tutia" is evidently derived. It was known in ancient India from the 3rd century B.C. as it has been mentioned in the Charaka and the Sushruta where it is used as an ingredient of external applications for the treatment of ulcers, leprosy, &c. It would be noted in this connection that not only *tutthwam* but *kāsisha* or green vitriol also has been mentioned in these works showing that the difference between these two kinds of vitriols was recognised in ancient India at a time when the ancient Greeks and Romans were ignorant of it. It was also known in later times as *mayurtutthwam* and *sasyaka* (मयूरतुत्थम्) and (सस्यक).

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That blue vitriol yields copper on heating with organic substances and borax in closed crucibles was discovered in India in the 12th century, as we find the following formula in *Rasārnava*—"Take blue vitriol and one-fourth its weight of borax and soak the mixture in the oil expressed from the seeds of pongamia glabra for one day only and then place it in a covered crucible and heat in the charcoal fire—by this process an essence is obtained from it of the beautiful appearance of coccinella insect."[¹] This formula is repeated in *Rasaratna-samuchchaya* which also prescribes that when blue vitriol is

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सस्तकस्य तु चूर्ण तु पादसौभाग्यसंयुतम् ।
करस्तैलमध्यस्थं दिनमेकं निधापयेत् ।।
मध्यस्थमन्वम्पायां मापयेत् कोकिलत्रयं ।
इन्द्रगामाकृति चैव सत्त्वं भवति शोभनम् ।।

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heated in a closed crucible with lime juice and borax, its essence in the form of copper is obtained.¹

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In the Bhāvaprakāsh (16th century) blue vitriol has been designated as a semi-metal (उपधातु) of copper as it is derived from copper. Dr. Ray remarks on this passage that "the nomenclature is in wonderful agreement with that adopted nearly two centuries later by Boerhave (1732 A.D.)."

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As regards the actual method of manufacture of blue vitriol in ancient India very little is known and no description of the process is to be found in alchemical works. As blue vitriol, however, is mentioned in medical works composed as early as the 3rd century B.C., it is very likely that it was obtained as a natural product or by-product in copper mines. An indigenous process of manufacturing blue vitriol along with ferrous sulphate and alum still survives in various parts of Rajputana where these sulphates are obtained by dissolving shales in water and crystallising from the solution obtained. The process was thoroughly examined and described by Colonel Brooke.² Ball in his Economic Geology of India writes—"In 1864 there were twenty of these factories at Khetri and about double the number at Singhana. The broken shale from copper mines which contains the salts is placed in earthen gharās, together with the crusts from the refuse heaps of previous lixiviations and water is added. The gharās are arranged on ledges prepared for the purpose on the heaps of refuse.

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"Each charge of shale is exposed to three changes of water and itself is changed from one gharā to another till it has taken up the sulphates from seven different steepings. It is then of a thick dirty-bluish colour and is taken to the boiling house where it is boiled in earthen gharās; when sufficiently concentrated it is left to cool and then sticks being introduced the

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1. नियुक्त्याल्पटङ्कण्या मूषामध्ये निषिच्य च । ताम्रं परिज्ञायं सर्वैर्गुणैर्युतम् ॥ Rasaratna-samuchchaya 11, 135. Ray, History of Hindu Chemistry, Vol. I, p. 47.

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2. Brooke, Journ. As Soc, Beng., XXXIII, p, 525.

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blue vitriol crystallises on them. The mother liquor is then poured off, and again boiled and on the addition of saltpetre the alum crystallises at the bottom of the vessel. The residual sulphates still in solution are allowed to crystallise out by exposing the mixture to the sun."

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In later times copper sulphate appears to have also been prepared by the action of sulphuric acid (dāha-jala, lit, burning water) on metallic copper. We find the following recipe in the alchemical work Dhātukriyā (16th century)--"tuttham (blue vitriol) is obtained by the action of sulphuric acid on copper."¹ Sulphuric acid was obtained originally in the 13th century in India as an "essence of alum or green vitriol" by the distillation of these substances. The distillation of alum and green vitriol is described in Rasaratna-samuchchaya.² The word dāha-jala as an equivalent for sulphuric acid is evidently of later origin.³ This process of preparing copper sulphate by the action of sulphuric acid on copper was discovered in Europe by Glauber in 1648, so that India can claim priority in the matter of the discovery of this reaction by nearly a century.

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¹ ताम्रदाहजलयोगे जायते तुत्थकं शुभम् । Dhātukriyā.

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² Rasaratna-samuchchaya, II. 54 and 65.

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³ Dr. Ray has evidently failed to interpret the meaning of this passage correctly. He has rendered the passage as follows--"Copper in combination with the burning water gives rise to tuttha (green) vitriol." This interpretation is evidently meaningless owing to the rendering, possibly through oversight, of 'tuttha' as green vitriol instead of blue vitriol or copper sulphate. The synonym "burning water" for sulphuric acid is very apposite and reminds one of the synonyms of "aqua fortis" for nitric acid and "aqua regia" for nitro-muriatic acid. That sulphuric acid was used for dissolving metals is independently shown by the following passage in Yasodhara's Rasaprakāsa-sudhākara--"the essence of alum is to be used for treating (dissolving) metals and not as a medicine (तत् तुवरी सत्त्वं धातुवादार्थे चोपध नौमपच्यते )."

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Of the other compounds of copper, the chloride and the oxide were incidentally prepared by heating copper with common salt and the metal respectively but not as separate compounds.

Copper Flame

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Every student of Chemistry knows that copper or compounds of copper when presented to the flame colour the flame blue. This fact is recorded in the Rasārnava (12th century) which states—copper flame is blue (शुलव नीलनिभा).

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