The Scottish Salt Company manufactured salt at Prestonpans until 1959. The company had diversified into several other products including 'oil of salt' or aqueous sodium sulphate, which was sold as a topical medicine.

This is a colourless glass bottle containing clear liquid. There is a paper label printed in black and red reading: OIL OF SALT/ TONIC FOR TIRED FEET/MOST RELIABLE CURE, etc. The bottle has a cork and metal stopper and is cracked.

Oil of salt is also known as Glauber's Salt, after the chemist who first described its properties. It was naturally formed in saltworks by reaction of salt (sodium chloride) with sulphur oxide fumes generated from burning coal. It was once used as a liniment for rubbing down horses.