How did Joseph Black’s ideas about latent heat relate to James Watt’s steam-engine work?

Joseph Black’s research into latent heat—the energy absorbed or released during a phase change—was instrumental in James Watt’s development of a more efficient steam engine.12

While repairing a Newcomen steam engine, Watt observed significant energy wastage. He realized that the engine's primary defect was the loss of latent heat, which occurred because the cylinder was repeatedly heated and cooled to facilitate steam condensation.2

Applying the concept of latent heat, Watt concluded that condensation must occur in a separate chamber to keep the main cylinder hot while the condenser remained cool. This innovation, the separate condenser, prevented the massive energy loss inherent in earlier designs. Although Black and Watt were friends and colleagues at the University of Glasgow, they maintained that their respective scientific and engineering breakthroughs were achieved independently.21