Limiting mA on 9v Batteries in Series
You can use a resistor. You have 54V so 13K would limit it to about 4mA. Whether it gets up to 1mA or not would depend on the solution conductivity. 

Distilled water is a pretty good insulator but once it gets some ionic contamination it will conduct much more. You could use a multimeter and a 10K pot in series with a resistor of a few K to fool with it.