{'fraction_non_alphanumeric': 0.015081206496519721, 'fraction_numerical': 0.018561484918793503, 'mean_word_length': 5.120567375886525, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The Historical Background: Molecular Theory as of 1900

The task of this chapter is to explain the sense in which molecular theory—both molecular-kinetic theory and chemical-molecular theory—were still viewed as hypotheses as of 1900 and why the evidence bearing on them during the second half of the nineteenth century was insufficient for them to have achieved standing beyond this. The chapter reviews the strengths and limitations of the evidence in question, taking advantage of two widely read textbooks in physical chemistry published in the 1890s by Wilhelm Ostwald and Walther Nernst and a uniquely comprehensive review of the evidence pertaining to the kinetic theory of gases, by O. E. Meyer, published in 1899. This background defines the historical context within physics and chemistry for the developments covered in the remainder of the monograph.