I am wondering what this container is used for. It was empty when I bought the car, and I was unsure of what liquid it was supposed to contain. It is on a 86 base model.

 

Sub Zero starting assist. Throw it away as Mazda had a TSB to disconnect the system.
From what I remember there is a valve in the intake that needs to be removed and a block-off plate installed,
or remove line and cap.