What did Joseph Black discover about latent heat?

During the Scottish Enlightenment, the chemist and physicist Joseph Black made a fundamental breakthrough by distinguishing between the quantity of heat in a body and its temperature (intensity). He realized that substances can absorb heat during a phase change without an increase in temperature, a phenomenon he termed latent heat.1

Black demonstrated this by observing that ice remains at its freezing point while melting, despite absorbing heat at the same rate as a warming liquid. He calculated that the heat required to melt a specific quantity of ice would have otherwise raised the temperature of an equal amount of water by 78 °C (140 °F), identifying this as the latent heat of fusion. He subsequently extended these experiments to measure the latent heat of vaporization. This discovery was significant for the development of the steam engine, as it provided a scientific basis for understanding the energy dynamics involved in phase transitions.12