Guncotton is an explosive. It is obtained when cotton or purified wood cellulose is soaked in a mixture of sulfuric and nitric acids. By 1846, C. F. Schonbein, a German chemist, had discovered the process for making guncotton. After the cotton is soaked in the acid mixture, it is drained and washed. Then, it is boiled in water to remove the acid and impurities. The cotton is ground to a pulp and drained. It is pressed into small slabs, or blocks, while damp. It may be dried in air, either after boiling, or after it has been made into blocks.