| Summary: | Evidence for the existance of volcanic lightning is produced from a literature survey and the charge sources which have been suggested are listed and those, of the 18th and 19th centuries, which involved boiling water are reviewed in detail. Studies of saline contact charging, undertaken by Blanchard et al, when Surtsey emerged in 1963 are reviewed and lead to the continuation, in this investigation, of the Leidenfrost form of boiling and the discovery of an associated charging process. This discovery resolves a two centuries long dispute as to whether the Leidenfrost phenomenon of boiling produces charge as well as showing its important relevance to volcanic lightning where solution contact charging is in evidence. The mechanisms by which charged particles are emitted and formed into hollow solute spheres have been investigated and their charge and size distributions determined. Their structure has been compared with the structure of particles produced by flash boiling and spraying of saline solution. The energy conversion involved in the particle emission mechanism has also been studied. Charging mechanisms and some charging processes have been reviewed and by comparing results from other investigations speculations as to which mechanisms produce charge in the Leidenfrost process have been attempted. The comparison of results leads to the suggestion that Blanchard's observations are more likely to be Leidenfrost boiling than, as he assumed, flash boiling. The high average charge per particle of 10<sup>-14</sup>C on particles from Leidenfrost boiling indicate that the number density is smaller, by a factor of 10<sup>4</sup>, than that previously suggested to produce the fields measured in volcanic clouds. Exploratory experiments have established that in addition to saline solution other aqueous solutions will also produce charge.
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