1) You certainly DO NOT use the books sugested above!
2) Aspen used the REFPROP engine supplied by NIST. Better to go directly to NIST
3) Best is to use REFPROP which is based on reference correlations. For hexane we ha ve developed
Michailidou E.K., Assael M.J., Huber M., Abdulagatov I., and Perkins R. “Reference Correlation of the Viscosity of n-Heptane from the Triple Point to 600 K and up to 248 MPa”, J. Phys. Chem. Ref. Data 43:023103:1-13 (2014)
DOI: 10.1063/1.4875930
You can find values there. If you can not find it contact me ([email protected]) or if you just want two values contact me again. This way you will know that you have the best available data, and not tables of suspicious origin..
You can use simple software available on the internet named "Physprops", just enter the element or compound and give the desired pressure and temperature and find the required properties.