Oxygen-free storage for pyrite speciments

Dr Caroline Buttler (UK) Oxygen is responsible for the majority of chemical reactions that lead to the decay and degradation of museum specimens; the corrosion of iron and the fading of many pigments when exposed to ultraviolet light could not occur without the presence of oxygen. It is also essential for the life forms responsible for biological decay such as insects, fungi and bacteria. The most common oxidation reaction affecting geological specimens is pyrite decay, which damages specimens containing pyrite or marcasite.  Pyrite decay occurs when the sulphide component in these minerals oxidises to form ferrous sulphate and sulphur dioxide, and can result in the complete destruction of the specimen and the associated labels and packaging materials. If pyrite specimens can be stored without oxygen then deterioration could be prevented. Fig. 1. Ammonite specimen with pyrite decay (©National Museum of Wales). The technology to produce oxygen-free environments to museum standards has burgeoned in the last few years. Nitrogen and other inert gases such as argon and helium have been successfully used to display specimens without oxygen, but it is costly and only used for rare or valuable objects. For example the American Charters of Freedom, which include the Declaration of Independence, the Constitution and the Bill of Rights, in the Rotunda of the National Archives Building in Washington, DC, are displayed in cases inside which an anoxic environment has been created containing a humidified argon atmosphere at 19°C. Anoxic storage can also now be achieved relatively cheaply and efficiently with … Read More