Halloween would not be the same without a chemist or two. It is the night when the veil between the living and the dead is said to be at its thinnest. Around 2,000 years ago, the Celts, including those right here in Scotland, celebrated Samhain to mark the end of the harvest. Bonfires were lit and masks worn to confuse wandering spirits believed to slip through from the ‘other side.’ Later, the Christians had their go, renaming 1 November as All Saints’ Day, with All Hallows’