One of the great achievements of neutrino physics was the discovery of solar neutrinos in 1968 through the Homestake underground experiment. This experiment exploited a radiochemical method based on the chlorine-argon process of inverse beta decay suggested by Bruno Pontecorvo in 1946 during his work in the classified Canadian nuclear project. In this paper, we study the emergence of the method. We focus on the role played by the problematic status of the neutrino and its antiparticle in its field of application and the influence exerted by the contemporary models of energy production in the sun. We also provide evidence that a first germ of this radiochemical method, in the form of a chlorine-sulfur process, was suggested in a paper published by Richard Crane in late 1930s.

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