What was the first coolant in refrigeration?

The first coolant used in refrigeration was ether, specifically diethyl ether, which was employed in the early 19th century. It was later replaced by other substances due to flammability and toxicity concerns. Subsequent coolants included ammonia and carbon dioxide, which offered better safety and efficiency for refrigeration systems. These advancements paved the way for the development of modern refrigerants used today.