The Proceedings of the Eighth International Conference on Creationism (2018)

and gases and found that it varied from 0.1 to 0.5 mg for a single discharge. While the reactant storage and delivery system is driven by muscle contraction, the reaction chamber is in fact rigid. Eisner and colleagues (Dean et al. 1990) reported spectrographic measurements of the discharge using seven beetles (45 discharges) and they concluded that the average discharge duration was 11.9 ms. The actual time elapsed was 2.6–24.1 ms, with 2–12 pulses per discharge recorded and thus a mean of 6.7 pulses per discharge. The frequency of the pulses is reported to range from 368 to 735 Hz, with the mean value at 531 Hz. The average velocity of the spray emerging from the tip of the beetle’s abdomen was measured with a high-speed camera to be 11.63 m/s (ranging from 3.25 to 19.5 m/s), and the spray can reach as far as 20–30 cm. Professor Eisner using electron microscopy was able to show that the beetle has twin combustion chambers (fig. 3) into which the combustible reactants are fed down a thin tube. This inlet tube is pinched under high pressure and acts as an inlet valve to stop the flow of reactants continuing during the combustion part of the cycle. Work with the team at Leeds (McIntosh and Beheshti 2008) also showed that there was also an exhaust valve which caused a membrane to lift at high pressure, so that there are in fact two valves controlling the ejection of the hot mixture of vapour and liquid (fig. 4). The ejected fluid is in fact primarily hot water and steam heated by the reaction of roughly a 25% mixture of the chemicals hydroquinone and hydrogen peroxide (Beheshti and McIntosh 2007a). And recent experimental work by another group at MIT (Arndt et al. 2015) led by Dr. Christine Ortiz has shown that the ejections are made with both of the twin chambers operating together. Furthermore a detailed analysis of the incoming glands carrying the reactants to the combustion chamber have now been made showing that the reactants come a reservoir chamber along fine tubes into the combustion chamber. The intricacy of these tiny parts of the system, all of which must be working to make the ejections take place, is an example of the irreducible complexity of the chemical burning and ejection process. All of this is completely independent of the digestive system of the bombardier beetle. 2. Chemistry Much of the early investigations on the chemistry of the beetle were performed by Schildneckt (Schildneckt and Houlebek 1961). His work showed that hydroquinone and hydrogen peroxide were being combined to produce benzoquinone and water. The aqueous solution of reactants is stored in a reservoir, and is composed of hydroquinone (C 6 H 6 O 2 ) at a concentration of 25% and hydrogen peroxide at a concentration of 10% - concentrations assumed to be by mass, see Schildneckt and Houlebek (1961) and Aneshansley et al. (1969). Fig. 5 shows a schematic representation of the beetle’s discharge apparatus including the reservoir and the reaction chamber. When the reservoir is squeezed, the mixture of reactants is introduced into the reaction chamber through a valve, which is opened in the first part of the cycle. Once the reactants are present in the chamber, the enzyme catalysts (catalase and peroxidases) are introduced from the combustor walls. An extremely fast catalytic reaction then takes place. While the hydrogen peroxide is decomposed with the help of catalase to water and free oxygen, the peroxidases play a role in the oxidation of hydroquinone. The reaction mechanism described by Aneshansley et al. (1969) can be described by the global chemical reaction: C 6 H 6 O 2 ( aq ) + H 2 O 2 ( aq ) → C 6 H 4 O 2 ( aq ) + 2H 2 O ( l ) (1) and it can also be described in three most important decomposition steps: C 6 H 6 O 2 ( aq ) → C 6 H 4 O 2 ( aq ) + H 2 ( g ) (2) H 2 O 2 ( aq ) → H 2 O ( l ) + ½O 2 ( g ) (3) H 2 ( g ) +½O 2 ( g ) → H 2 O ( l ) (4) where “ aq ” means aqueous solution, “ l ” means liquid and “ g ” means gas. Note that equations (2)–(4) are not to be regarded as the breakdown of equation (1). Rather they represent the salient reactions of a much larger number of reactions, and the important point is that the sum of the enthalpy changes of equations (2)–(4) is equal to that of equation (1). The enthalpy of reaction at 25°C for equations (2)–(4) are ∆ H 2 = +177.2 kJ/mol, ∆ H 3 = −94.5 kJ/ mol and ∆ H 4 = −285.5 kJ/mol respectively, with a negative sign meaning there is heat given off and a positive sign meaning that energy is used up. So equation (2) is considerably endothermic and uses up energy to get the hydroquinone to break up. Equation (3) McIntosh and Lawrence ◀ Design of the bombardier beetle ▶ 2018 ICC 269 Figure 1. African bombardier beetle Figure 2. The beetle defence mechanism deters ants (shown), birds, spiders and frogs which may attempt to prey on the beetle.