Do you have anything more to go on than this paragraph in Google books search? I have created all sorts of specialized properties for unusual substances. Let me know what you have and I'll see what I can do.

Thank you very much Sir

I presume you need much more than the boiling point. If you scour the Web and find everything that is available (for example: molecular weight, critical temperature, critical pressure, viscosity or thermal conductivity at any point), I could fill in the gaps using various estimation methods. Right now the only thing I have to go on is 260°C boiling point at 1 atm. There are several compounds with similar names as well as trademarks (for example, DOWTHERM). You need to sort all this out before I can help you. I have attached a paper I found while searching for "Diphenyl-Diphenyl oxide Eutectic" on the Web, which may or may not be related to the compound you're interested in.

I hope you are well.

My system works at high temperatures, around

350 °C so water is recommended because of its low stability at high temperatures.

I use Thermex (Diphenyl-diphenyl oxide eutectic) as a working fluid for the heat pipe because of its stability in my temperature range of operation.

Attached is the list I found in this book (P. D. Dunn and D. A. Reay, "Heat pipes," 1982) but it lacks the conductivity of the fluid in the vapor state.

Kind regards

This is exactly what I needed. I will get back to you soon.

The property functions all have the right shape and typical approach to the critical point and also compare reasonably with the tabulated values. You can use the functions (VBA macros) in the spreadsheet to calculate any value at the desired temperature. Let me know what you do with the properties so that I can follow your work. Glad to help out. More details on property estimation can be found in this book https://www.amazon.com/dp/B07Q5L1CHT which will be free on March 23.

Thank you very much Sir

I will send you the update as soon as possible.

I need these properties because I use Thermex as a working fluid for the heat pipe, the system is used to generate high temperatures for steam generation.

I choose Thermex for its high stability and high merit number.

Thank you, good information