Ancient Indian's How To Produce Zinc ?

 Zinc using cultures appeared in the Indian sub-continent around 6th millennium BCE. Subsequently, copper metallurgy is well attested to at various sites by the 4th millennium. Besides copper-bronze, these ancient societies were also aware of various other metals like gold, silver, tin. Even deliberate production of iron goes beyond the 1st millennium BCE. Compared to the great antiquity of these metals, in a historical perspective, regular production of zinc and brass and distillation of zinc is very late.

Zinc is a difficult and enigmatic metal. In the earliest cementation process finely divided copper fragments were mixed with roasted zinc ore (oxide) and charcoal (a reducing agent), and heated to 1000°C in a sealed crucible. The zinc vapour thus formed dissolved into the copper fragments yielding a poor quality brass, zinc percentage of which could not be easily controlled. Reduction around 1000°C is crucially important as below 950°C no zinc is produced. If the temperature was raised above 1083°C, copper melted and flowed down to the bottom of the crucible. Because of such properties, pure zinc smelting was mastered so late.
Zinc was largely used in manufacturing brass. It seems that there has been some confusion about early occurrences of zinc, brass and zinc extraction by distillation process. Brass, an alloy of zinc and copper, is known for a long time and can be produced accidentally as has been reported from China and West Asia. In India also there are examples of brass from Lothal and Atranjikhera in 3rd and 2nd Millennia contexts. The ancient Persians attempted to reduce zinc oxide in an open furnace but they failed. In fact zinc distillation was an advanced technique, perhaps derived from Ayurvedic preparations and a long experience of alchemy. Regular zinc production in China began only in 16th Century AD, which was perhaps based on the Indian technique. It required heating the zinc ore in a controlled manner and then condensing the vapours through a retort in a receptacle.

The earliest 14C dates (uncalibrated) for the Zawar mines are PRL 932, 430+100 BCE and BM 2381, 380+ 50 BCE. Old workings at Rajpura-Dariba (375 BCE) and Rampura-Agucha (370 BCE) confirm the mining of lead-zinc ores in the southern Rajasthan during the fifth-fourth centuries BCE onwards.

It has been demonstrated experimentally that brass produced by the cementation process could not contain more than 28 percent zinc. For producing higher zinc content brass, one requires pure zinc to be mixed with copper, which could have been possible only after discovery of zinc as a separate metal and its preparation by a process such as distillation. Though there is considerable amount of literature available on archaeometallurgy, particularly on copper and iron technologies, there is very little literature on zinc, barring few papers by Craddock and his collaborators on zinc and brass. The discovery of zinc distillation was a momentous invention and a remarkable contribution of India in the global history of science and technology. A book on the metallurgy of zinc, brass and zinc distillation in India would, therefore, fill a lacuna in the history of science.

Zawar mines show a continuous development of zinc smelting technology from mid-1st first millennium BCE and finally evolved into the sophisticated distillation process in the twelfth century AD. I propose to study this story of gradual evolution of zinc technology in India. And also how it spread all over the world. 

The Vedic literature, for example, Satapatha Brahmana and Atharveda while dealing with immortality speak of gold, which has everlasting lustre and Soma, a plant of exhilarating quality, was also held in high esteem in the society. Such early references to metal are indicative of a long tradition of alchemy in India. According to the Upnishadic doctrine the five elements (earth, water, fire, air and a ubiquitous all pervading principle) give rise to or constitute the human body. The Ayurvedic Samhitas deal with the formation of human body and all related issues e.g., physical processes of digestion, disease and so on. Ayurveda is more concerned about the health and longevity of human body. The Charaka and Shushrut Samhitas deal with vajikarana (increasing virile power) and rasayana (enhancing longevity), for which various compositions and practical procedures have been mentioned. Unlike the principle of alchemy (rasasastra), in which mercury and sulphur play very important role, the Ayurveda speaks about elaborate methods of herbal elixirs, treatment of diseases and surgical practices. The more popular name for brass was riti or ritika; the word was probably derived from harita or yellow, which had been a synonym for gold in the Vedic literature. The word was chosen on account of the yellow colour of gold-like brass. The writings of Manu, Yajnavalkya and Patanjali of the pre-Christian era also refer to bronze (kamsya) and brass (ritika). Both Kautilya's Arthasastra and the earliest Indian brass of Taxila belonged to fourth century BCE, while the earliest 14C date of Zawar Mine is 430+100 BCE. The Arthsastra is the earliest firm literary evidence for the production of metallic zinc on a regular basis in India, which mentions brass as arkuta and liquid ore and refers to burning of a rasa (metal) to produce an eye salve or zinc. The text also records how various metals were obtained for example, tutthodgata (silver) was extracted from tuttha, which was refined 17 times to overcome tuttha. The text reveals that the Directors of Mining and Metal were supposed to examine old mines, locate new ones by examining the physical properties of the ores and establish factories for copper, lead, tin, brass, steel and so on. By the early centuries of the Christian era the Ayurvedic practices were very common in the society.

It seems that the Chinese and Indians considerably shared alchemical knowledge in the Old World as amritadhatu (mercury or the metal of immortality) was often referred to in Mahayana (Buddhist text). In Indian alchemy one finds large number of rasas (minerals) and rasendra (mercury) is called maharasa (king of minerals). They have been classified into maha (superior) and upa (subsidiary) rasas (minerals). The maharasas are known as abhra (mica), vaikranta (kimberlite dust), masika (pyrites), vimala (chalcopyrite), adrija (bitumen), sasyaka (copper sulphate or a compound of copper) and capala (zinc carbonate). Various medicinal plants have been referred to in Rasarnavakalpa, which were used for transmutation and processing of the metal.

In fact a large body of ancient Indian literature refers to various types of metal that were used in different periods. In the epics e.g. Mahabharata and Ramayana, brass and the bell metal have been termed as kamsya, the utensils of which were used for milking and drinking. However, in Grihyasutra brass is called either arakutah, riti or pitala, perhaps indicating different types. Pitala is generally considered to be brass. Among these terms riti seems to be yellow brass, bell metal. According to Gobhila Grihyasutra the Vedic students's hands were supposed to be dipped in bell metal vessels. In Jain literature zinc is known jasada. Since brass has yellow glittering appearance it was also sold as false metal gold. The Ras-Ratnakara of Nagarjuna (a well known chemist of the Satvahana period, fourth century AD), has been referred to as one of the best ancient literary records of brass and metallic zinc (rasaka) production. It also informs about production of brass, cementation process and metallic zinc. The text was probably compiled in its present form in the seventh or eighth century AD. In later periods zinc was also known as yasada, yasadayaka, yasatva.

The Rasaratnasamucchaya, a fourteenth century alchemical text, reveals that the Indian alchemy was not only confined to the principle of mercury and its compounds but also to a large number of other minerals. It reveals names of scores of celebrated alchemists like Nagarjuna, Govinda and others. The rasvidya (alchemy) was kept closely guarded secret and confined to devout practitioners only. It explains how a laboratory should be established in a place that is rich in medicinal herbs and several types of furnaces, instruments, kosthi (for extraction of essences), bellows, retorts etc. The Rasasastra text particularly reveals various kinds of instruments, types of furnace (e.g., dola yantram, kosthi yantram, musa ynatra, adhapatana yantram, svedani yantram, tiryakpatana yantram), and chemical processes used in smelting operations. The tirakpatana yantram (which means distillation by descending) was particularly used for distillation purpose. McNeil writes that this word is so close to the Latin nomenclature that it tempts one to conclude that links existed between European and Indian alchemical workers. It is believed that the ancient Rasasastra (alchemy) developed as Iatro-chemistry during the medieval times when the famous book Rasaratnasamuchchaya was compiled. The Ain-i-Akbari, a medieval text, also refers to ruh-i-tutiya i.e. zinc found at Zawar in Rajasthan. It is quite likely that ruh-i-tutiya may have been derived from the same term tuttha of Arthasastra.

There is thus ample evidence of early Indian literature indicating that a wide range of alchemical practices were prevalent in ancient India. The Rasaratnasamucchaya (14th century) clearly mentions that a particular type of furnace was used for distillation process.

The innovation of distillation technique of zinc in India is a glorious chapter in the global History of Science and Technology. I would like to explore and document the gradual development of Indian alchemy, with particular reference to zinc and brass, which led to the distillation technique, not only in the Zawar area, but al over Rajasthan.