Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Investigations on the Staudinger explosion and its prevention Alexander Schaberg a, ⁎ , Roland Goertz a , Stefan Bräse b,c a Bergische Universität Wuppertal, Germany b Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT) Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany c Institute of Toxicology and Genetics,Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany ARTICLE INFO Keywords: Alkali metals Halocarbons Energetic system Sodium Explosion ABSTRACT About 100 years ago, Hermann Staudinger discovered a series of "strange explosions" involving alkali metals and halocarbons, which were not only very violent, but they were also initiated by mechanical shocks. Later these explosions were referred to as “Staudinger explosions”. However, most of the resulting investigations by Staudinger were lost during World War II. Over the last 100 years, these explosions have been used as classroom experiments, but they pose a significant threat in chemical laboratories when chlorinated solvents are inad- vertently mixed with alkali metals. To date, no simple methods are known to desensitize such abnormally high impact-sensitive systems, so that resulting interventions are rare, but demand lots of time and effort to de- sensitize these systems. Due to the particular threat, it was investigated how such a high-energy system can be phlegmatized or desensitized. The admixture of an indifferent solvent, such as an alkane, has proven to be useful, which under favorable conditions leads to an increase in the impact energy required for the explosion by more than 300%, thus making the mixture manageable for application forces. 1. Introduction The reaction of metals with oxidizing reagents has been known for centuries and is used for many purposes (metallurgy, fireworks etc.). However, the mixture of alkali metals with chlorinated solvents is a more recent discovery. After Hermann Staudinger described the for- mation of a highly explosive system about 100 years ago together with Eugen Anthes in Karlsruhe. After early experiments with oxalyl bromide or oxalyl chloride and sodium as well as potassium-sodium alloy for the preparation of dicarbon oxide [1], he continued his research on the explosiveness of halogen derivatives with alkali metals. In these early experiments, it has already been found that no or only superficial re- actions can be observed when oxayl chloride is poured over alkali metals. There were, however, violent explosions when the test vessels were dropped. In the case of distillation experiments, the scientists found that the halogen derivatives could be extracted without danger of explosion and thus concluded a certain robustness of the systems against thermal influences. The nature of their initiation is particularly special to these explosions: While these systems are relatively in- sensitive to thermal influences, they are all the more sensitive to impact (See Fig. 1). Stimulated by accident reports of chemist colleagues, Staudinger carried out extensive investigations on these reactions. The resulting experiments showed that the sensitivity of the systems is related to the electronegativity of their components. Thus, a system containing po- tassium may react on contact. In the case of sodium and lithium, stronger impacts are required. Among the halogens, chlorine was the most reactive, followed by bromine and iodine [2]. We were not able to stimulate any explosions with fluorinated starting materials. In these earlier experiments, potassium was introduced into tetra- chloroethane or pentachloroethane. After 20–60 seconds, an explosion occurred, the duration partially correlating with the temperature of the solvent [1]. These observations led Staudinger to conclude that a kind of cova- lent bond is formed between the alkali metal and the halogen derivative (cf. (1)), and the intermediates undergo secondary reactions to form alkali halides. Among these, he assumed an extremely labile inter- mediate. (1) Depending on the alkali metal used, this system showed different shock sensitivities, which are shown in Table 1. Solvents containing sulfur or oxygen as the heteroatom could be https://doi.org/10.1016/j.jhazmat.2018.12.097 Received 19 September 2018; Received in revised form 11 December 2018; Accepted 24 December 2018 ⁎ Corresponding author. E-mail address: schaberg@uni-wuppertal.de (A. Schaberg). Journal of Hazardous Materials 367 (2019) 375–380 Available online 26 December 2018 0304-3894/ © 2018 Elsevier B.V. All rights reserved. T