How did Joseph Black distinguish heat quantity from temperature?

Joseph Black distinguished between the quantity of heat and its intensity, or temperature, by observing how substances absorb heat during phase changes and temperature variations.1

He realized that thermometers measure intensity, but the total quantity of heat can be determined by monitoring temperature changes over time as a body is heated or cooled. To demonstrate this, Black conducted experiments comparing the warming rates of ice and water. He observed that while ice was melting, it absorbed significant heat without an increase in temperature, a phenomenon he identified as latent heat.1

Furthermore, Black observed that equal masses of different substances require varying amounts of heat to achieve the same temperature change. This insight led him to establish the concept of specific heat, further clarifying that temperature alone does not account for the total heat energy contained within a body.2