Saltpetre a mineral substance gathered from sandy areas of Bengal and Bihar was an important item of export from Bengal up to mid-nineteenth century. Also used in drinks as a cooling agent, it is an important ingredient for manufacturing gunpowder, glassware, dye and some drugs. Its freight charge was zero because it was used as ballast of ships. Saltpetre, therefore, had a huge market in Europe and until the end of the eighteenth century occupied a very major export item carried by the Europeans in Bengal.

The demand for Bengal saltpetre in the European market was almost unlimited. Consequently, there was intense competition among the Dutch, the English and the French companies who tried to secure as much saltpetre as possible from the assamis (saltpetre workers). The competition for the item was not confined to European companies only. The government and high nobles of the Bengal subah often tried to become middlemen between the assamis and the European buyers. But the attempt was not always successful because the European companies, in order to keep the price low, themselves made cartels in order to eliminate the local competitors from the market.

Historical evidence about the amount of the export of saltpetre is scarce. However, a circumstantial data about saltpetre export made by the English east india company for five years from 1733 will indicate the trend of its volume at the time.

Year Quantity (in maund)
1733 36,246
1735 31,778
1736 24,190
1737 31,698
1738 46,746

Source  Sukumar Bhattacharya, The East India Company and the Economy of Bengal, 1704 - 1740, (London : 1954), p. 151.

Besides the English East India Company, all other European companies exported saltpetre more or less in the same volume. The price of saltpetre normally varied from Rs 3 to Rs 4 per maund, while under competition it rose to as high as Rs 10 per maund in the early eighteenth century. Therefore, saltpetre was a real El Dorado not only for the foreign companies, but also for its manufacturers and the government. With the invention of modern chemicals the use of saltpetre came to a virtual end in the end of the nineteenth century. [Sirajul Islam]