The 70s really were another country - see also: chemistry sets. These are pale and anodyne things now with a mere handful of bland household-level chemicals - assuming you can even find one in a toy shop at all. But as a lad these were both readily available and full of dozens of intriguing substances that would send a modern health and safety wonk into apoplexy. Who among us did not incinerate all of the supplied magnesium in a short series of pyrotechnic orgies? Merit was the go-to brand in the UK, but I also had a set from an American company that contained, among other exotica, potassium ferrocyanide. This is decidedly non-lethal but the very name never failed to send a poisoner's frisson through my teenage brain.