# Who introduced 1/T=δS/δU and when?

Who first defined temperature $$T$$ such that $$\frac{1}{T} = \frac{\delta S}{\delta U}$$, and where and when?

It could not have been Thomson, right? He did not have an entropy concept. Clausius?

• One should look at work of Poincaré who has developed a good part of the mathematical apparatus of thermodynamics. – Jean Marie Becker Apr 14 at 21:18