This 473ml/16 oz bottle of Kodak Photo-Flo 200 Solution is a wetting agent used to minimize water marks or streaks that can appear during film drying. It is used after the final wash when processing films to decrease the water-surface tension and promote faster, more uniform drying.
The Brownie Camera Guy says:
Kodak Photo-Flo is what I have always used as a wetting agent. It works and a bottle will last for years. I use 1/4-1/2 cap-full as a measure in a tray with water after each film processing session. I never use it in the tank itself.