In 1846, a chemist wiped up spilled acids with an apron and found a dangerous new cotton

Discoveries in science are usually attributed to thoughtfully devised experiments, but not all discoveries in chemistry were made with the intention of gaining insight into how things worked. For instance, in 1846, a German-Swiss scientist named Christian Friedrich Schönbein discovered the properties of guncotton in a rather interesting fashion while working with strong acids in Basel. It is widely reported that Schönbein had spilled an acid on the floor during his experiments and used his cotton apron to clean it up; subsequently leaving the apron to dry. It is at this point that Schönbein observed the apron spontaneously ignite and burn rapidly, only to realize that the apron now consisted of a new material called nitrocellulose. This discovery is considered to be one of the most famous serendipitous discoveries in the history of chemistry due to the radical transformation of a familiar substance.

A spill, an apron, and an unexpected reaction

The history begins in Basel around the middle of the nineteenth century, when Schönbein began experimenting with concentrated nitric acid. According to the historical record of nitrocellulose creation archived at the Southern University of Science and Technology, Schönbein accidentally poured nitric acid and, having cleaned it with a cotton apron, let it dry. The surprising result that soon followed was that the apron burst into flame at a surprisingly high rate of speed. There were two very important features about this experiment, however.

Firstly, the cotton itself had undergone an irreversible change. Indeed, according to the aforementioned review, Schönbein had created more than just cloth; his cloth had been chemically transformed, as the cotton fibers contained cellulose that reacted with acids and became nitrated. This meant that the chemical qualities of the substance had changed drastically, and not only in terms of flammability. Therefore, this accidental discovery provided one more proof that molecules could be changed on purpose. A substance, which was originally quite commonplace, became a whole other thing, something previously unseen.

How cotton became guncotton

The substance resulting from the reaction would eventually be known as nitrocellulose, or guncotton. Molecules reports in a review that nitrocellulose is one of the earliest examples of a chemically altered cellulose substance and adds that the discovery of nitrocellulose was a critical step in the evolution of energetic materials. The chemical process whereby cellulose was converted into a substance capable of producing energy much more rapidly than unaltered cotton.

Another review on nitrocellulose and energetic materials also mentions Schönbein as playing a key role in its discovery. According to the review, nitrated cellulose became immediately attractive due to its potential for explosive behavior and its ability to act as a propellant. The military community took particular notice of the material in that it seemed to offer certain advantages over gunpowder. The rapid development of interest in nitrocellulose reveals just how unusual the discovery seemed. Cotton was one of the most common and well-known substances at the time. The idea that cotton could be altered to produce an intense fire demonstrated the surprising possibilities in both chemistry and material science.

Why nitrocellulose proved both useful and dangerous

However, the same qualities made nitrocellulose dangerous. As the authors of the review Molecules say, nitrocellulose is unique in that it contains both oxidizers and fuels in its structure. Unlike common cellulose, which depends on oxygen available in the air for burning, nitrocellulose has a lot of what is required to burn already incorporated in its substance.

Thanks to these features, nitrocellulose can burn at a highly accelerated rate. The rapid release of energy produces effects that make the material quite useful. However, such a structure posed problems connected with the transport and storage of the substance. The history of development of nitrocellulose is full of attempts to make it more stable and manageable. However, these attempts were unsuccessful due to the nature of the discovery. The dual character of the discovery is what makes Schönbein’s apron story so well-known in the history of chemistry.

From laboratory accident to lasting technological influence

However, nitrocellulose did not stay in the realm of laboratories for long. Historical accounts of the development of nitrocellulose indicate its use in propellant, explosives, coatings, film, and other industrial materials. Over time, chemists developed improved manufacturing and stabilization techniques, enabling the more widespread use of nitrocellulose beyond its initial applications in weaponry. The discovery of nitrocellulose became another early instance of what would become a valuable scientific insight: accidental observations can become breakthrough discoveries only when scientists acknowledge their importance. Accidents in laboratories happen often enough, but very few of them alter the course of scientific development. In his case, Schönbein did not just create a mess. He noticed its potential and recognized the peculiar properties of cotton as an indication of something new.

The history of Schönbein's lab accident is still mentioned in many accounts of chemical research almost 180 years after the discovery, since it illustrates a common occurrence in the field of science. A normal substance exhibits unusual characteristics, a researcher notices it, and new knowledge emerges. This simple lab mistake led to one of the most important discoveries in the world of energetic materials.