Complex sentence: The overview of the organic bonds by Kekulé was necessary to understand the silicates, first refinements described by Bragg and Machatschki; and it was only possibly to understand a crystal structure with Dalton's atomic theory and Goldschmidt's explanations.
Split into simpler sentences: The overview of the organic bonds by Kekulé was necessary to understand the silicates, first refinements described by Bragg and Machatschki. And it was only possibly to understand a crystal structure with Dalton's atomic theory and Goldschmidt's explanations.