Immortality, saltpetre and Bengal’s first weapon of war

His father was the ruler of Fergana in Uzbekistan. Conspirators overthrew him and seized the throne. The king was killed. The son took refuge in the remote mountains surrounded by deep forests. From there, he carried out rapid raids, capturing small caravans to gather troops and resources. Each successful attack made him stronger. Later, he regained control of Fergana. Growing even more powerful, he advanced further south. At one point, he even conquered the whole of Afghanistan. Then he set his sights on India, like a bird aiming for its prey. His dream grew bigger. With a vast army and entourage, he arrived at the banks of the Indus River. At that time, the throne of India was held by Ibrahim Lodi — a formidable emperor. Defeating him required something extraordinary. That special thing the young man had acquired from the Turks: a large iron pipe with two wheels on either side.

When gunpowder was packed into the back of the pipe and ignited, the resulting explosion would propel a flaming projectile at tremendous speed from the mouth of the pipe. It would strike its target and destroy everything in its path — soldiers, shields, swords, elephants, horses, even massive buildings. The rulers of India were still unaware of this terrifying weapon. A huge cavalry and elephant corps gathered on the other side of the Indus. Emperor Ibrahim Lodi himself led them. His attitude was that the moment the young man’s forces crossed the river, he would crush them. He had already prepared every means to kill as many enemy soldiers as possible with bows and arrows before they could approach. But the Uzbek youth did not fall into this trap. Instead, he instructed his artillery to fire. The very first shot hit the mark. It struck none other than Ibrahim Lodi himself. With their leader dead, Lodi’s forces became disoriented. In a very short battle, Babur — the first Mughal emperor — conquered India. For Babur, the cannon was like a divine weapon. And to fire that cannon, gunpowder was needed. Behind the invention of gunpowder lies a curious story — the quest for immortality.

For ages, people have desperately sought immortality. Even after thousands of years, that hope remains unfulfilled. Let alone immortality, even the secret to living 100 years has not yet been discovered by medical science. Occasionally, a few people might surpass 100 years, but in such cases, luck and diet play more of a role than medical science. Moreover, lifestyle and inherited disease resistance also contribute to longevity. Since ancient times, scholars in various countries have practised alchemy in search of immortality. They sought to discover the elixir of life. But even after centuries of effort, scientists failed. However, those alchemists did lay the foundation for modern chemistry. But what if, in trying to make something to achieve immortality, one instead created a chemical capable of destroying humanity?

The incident dates back to the second century BCE. On the throne of China was Wu Di, one of the most influential emperors of the Han dynasty. In those days, kings and emperors were extremely indulgent — as they were in all countries. There are numerous examples of royal treasuries being emptied for their luxuries. So, it was only natural that such kings or emperors would want to conquer death. Wu Di summoned his kingdom’s researchers. He ordered them to quickly create an elixir of life for him. The researchers hurriedly got to work. They tried to make a potion mixing sulphur with potassium nitrate. But the result of this mixture was devastating. When the two chemicals came into contact, they exploded. However, the explosion wasn’t massive. History records no casualties in the incident.

Initially, the researchers did not pay much attention to the small explosion. They assumed that something meant to grant immortality might show a bit of fierceness! Surely, with a bit more effort, they would create the desired elixir. But despite many attempts, Wu Di’s researchers failed. So, they abandoned the project. Research on gunpowder was shelved for a long time. In the third century CE, some minor experiments resumed. But back then, gunpowder was used in religious rituals or fireworks. It was not yet used in warfare to kill people. In the eighth century, research into gunpowder reached its peak. It began to be used in warfare. The Chinese even created the world’s first rockets or missiles using gunpowder.

Even today, like in ancient times, gunpowder is made by mixing sulphur with nitrogen. The main compound used to make gunpowder is called potassium nitrate — commonly known as saltpetre, or sora. But calling it just saltpetre would be incomplete — the full name is Bengal saltpetre. A substance invented in China and first used in cannons by the Turks came to be associated with Bengal. Why? Behind this lies a history of war and exploitation. A history as tragic as indigo cultivation. The primary ingredient of gunpowder is saltpetre, combined with phosphorus and charcoal. As previously mentioned, saltpetre’s scientific name is potassium nitrate.

To make gunpowder, you must mix saltpetre, charcoal, and sulphur (or brimstone). Although potassium nitrate is the main ingredient, to produce explosive power, phosphorus or sulphur is essential. Saltpetre is a powerful oxidising agent. To trigger oxidation with it, fuel is needed. Charcoal and sulphur — known in Bengali as gondhok — serve as that fuel. Phosphorus ignites at the slightest heat. To sustain that flame, charcoal is needed. But how strong can ordinary fire really be? To cause an explosion, you need a large supply of oxygen and intense oxidation. That oxygen comes from potassium nitrate — what we are calling Bengal saltpetre. Gunpowder is made combining all of these.

The ratio of saltpetre, charcoal, and phosphorus in gunpowder determines which weapon it will be used in. In the 14th century, European gunpowder typically had equal parts of these three ingredients. But a few decades later, as weapons took on various forms and uses, the composition of gunpowder changed. For example, in the 16th century, gunpowder used in large cannons contained 50 percent saltpetre, 33.33 percent charcoal, and 16.67 percent sulphur. For smaller cannons, the proportions were 62 percent saltpetre, 25 percent charcoal, and 13 percent sulphur. For muskets, the ratio was 83.33 percent saltpetre, 16.67 percent charcoal, and 8.33 percent sulphur.

The atmosphere contains the most nitrogen. In other words, the key ingredient of gunpowder is already in the air. But for people in earlier times, extracting nitrogen from the air was extremely difficult. This difficult task was performed by a type of bacteria. However, more than atmospheric nitrogen, dead organisms, waste, and animal excrement were the main sources of nitrogen. These materials would rot, and bacteria would produce ammonia or nitrogen trihydride. Then, by removing hydrogen from the ammonia and adding potassium and oxygen, potassium nitrate would be created — what we now call Bengal saltpetre or potassium nitrate.

Potassium nitrate enriches soil when mixed into it. During the monsoon, it gets washed down to lower soil layers. After the monsoon, during the dry season, the water evaporates, but the potassium nitrate remains trapped in those lower layers. This saltpetre was then taken to factories and mixed with charcoal and sulphur to make gunpowder. Bengal was not yet divided. The province known as Subah Bengal included Bihar, Odisha, present-day Bangladesh, West Bengal, and Assam. Any product from this region was naturally identified with the name Bengal — just like how today, Jamdani from Tangail or Hilsa from Chandpur is recognised worldwide as Bangladeshi. The main production centre of saltpetre was Patna in Bihar. From there, it became known as Bengal saltpetre.

Moreover, this gunpowder was exported globally through the Chuchura port of Kolkata. That’s another reason for its name Bengal saltpetre. Both the Dutch and British had similarly named companies — first the Dutch East India Company, then the British East India Company. Later, the French East India Company was also formed — mainly to share in the trade of this divine weapon of Bengal. This region of ours was once the richest in the world, yet even then many of its people lived in poverty. On top of that, there was caste discrimination. Lower-caste Hindus were treated as untouchables. One such untouchable and poor group carried out the work of extracting potassium nitrate. They were called Nuniya, because saltpetre is a type of salt. In Bengal and Patna, nun was the word for salt. Like Bengal, in Patna too, salt was called "Nuun".

And because they collected salt known as saltpetre, this group was called the Nuniya. Their masters were the jotedar businessmen. These men raised cattle, and the Nuniya worked by taking the cattle far out into the grasslands to graze. As the cows and calves grazed, they would also defecate and urinate all day. Huge piles of dung and urine accumulated. Animal waste is a rich source of nitrogen, specifically ammonia. Through chemical reactions, that ammonia would become saltpetre. As a result, saltpetre crystals formed throughout the year in those fields. During the dry season, a white layer eight inches thick would appear under the dried heaps of dung and urine. The Nuniya would scrape up that layer of white earth from excrement.

The hardened dry earth was crushed into small pieces and mixed with water. The saltpetre dissolved in the water, while the soil settled at the bottom of the container. The saltpetre-infused water was then separated and repeatedly boiled to purify it. This saltpetre, through Portuguese, Dutch, and British traders, spread across the world. With Bengal’s saltpetre, intense warfare raged globally — especially in Europe. Even the American War of Independence saw Bengal saltpetre play a major role. Before that, it was due to Bengal’s saltpetre that the mighty French were defeated and the British established their dominance in Europe. But that’s a story for another day.

Abdul Gaffar Rony: Science writer