I’m not sure this that this is fair to phlogiston or the scientists who worked with it. In fact, phlogiston theory made predictions. For example, substances in general were supposed to lose mass when combusting. The fact that metals gain mass when rusting was a data point that was actively against what was predicted by phlogiston theory. The theory also helped scientists see general patterns. So even if the term had been a placeholder, it allowed scientists to see that combustion, rust and metabolism were all ultimately linked procedures. The very fact that these shared patterns and that phlogiston predicted changes in mass (and that it failed to predict the behavior of air rich in oxygen and carbon dioxide (although those terms were not used until late)) in the wrong direction helped lead to the rejection of phlogiston theory. There are classical examples of theories with zero or close to zero predictive value. But phlogiston is not one of them.
Edit: Said lost mass when meant gain mass. Metals gain mass when rusting they don’t lose mass. Phlogiston said they should lose mass but they actually gain mass. Also, fixed some grammar issues.
I’m not sure this that this is fair to phlogiston or the scientists who worked with it. In fact, phlogiston theory made predictions. For example, substances in general were supposed to lose mass when combusting. The fact that metals gain mass when rusting was a data point that was actively against what was predicted by phlogiston theory. The theory also helped scientists see general patterns. So even if the term had been a placeholder, it allowed scientists to see that combustion, rust and metabolism were all ultimately linked procedures. The very fact that these shared patterns and that phlogiston predicted changes in mass (and that it failed to predict the behavior of air rich in oxygen and carbon dioxide (although those terms were not used until late)) in the wrong direction helped lead to the rejection of phlogiston theory. There are classical examples of theories with zero or close to zero predictive value. But phlogiston is not one of them.
Edit: Said lost mass when meant gain mass. Metals gain mass when rusting they don’t lose mass. Phlogiston said they should lose mass but they actually gain mass. Also, fixed some grammar issues.