The Sinner and the Sandman - S5-E2
Factual error: Members of The Salvation Army do not gamble and do not buy lottery tickets.
Factual error: During the examination of the crime scene at the beginning of the episode, not one of the Crime Scene Officers or any of the police on site wear latex gloves. The supervising police officer picks up a vital piece of evidence - a small bag of jewellery - with bare hands! They have hopelessly contaminated the scene.
Factual error: When it's is revealed that The Omega Man is made of mercury, it is explained that it needs to be frozen to a temp of -38.87c, then it's shown being taken out of the freezer and the mold being removed with bare hands, which would be impossible at that temperature.
Chosen answer: It was a bottle of turpentine.
Methylated spirit, always coloured purple.