stuck & confused

[kastanok]

You have not messed up your game, don't worry.

You cannot combine the items yet - you will be able to when you next find a laboratory.

HINT

Spoiler below!

You have to find the right place to use the bucket. The key is NOT in the bucket, the water is used elsewhere.

SOLUTION

Spoiler below!

Look around for a broken pipe on a wall (to the right of the exit). You can either either pour the water down the pipe to wash the key out, or take the iron bar and knock it out.