The premier organization for Chemical Engineers in the United States is the American Institute of Chemical Engineers. Here are some of the most useful links on their site.
This series is an excellent place to find chemical and physical data about liquids and gases, including phase diagrams, triple points, liquid-liquid equilibrium information, and basic properties. It complements the DIPPR 801 files available through Knovel. We have the full series. Some of the more-often used items are listed below.
These books are generally stored in compact shelving due to their cost. You will need to request access using ILL.