Wilhelm Ostwald
Bancroft was trained by Wilhelm Ostwald and Jacobus Henricus van 't Hoff, and introduced a number of thermodynamic and colloid-chemical concepts into American physicochemistry. He is known for the Bancroft rule: a predominantly hydrophilic emulsifier stabilizes an oil-in-water emulsion, whereas a predominantly hydrophobic emulsifier stabilizes a water-in oil emulsion.