Symptoms are severe stomach pains, vomiting, coms then death. Repeated small doses can cause mental deterioration. Mercury Mercury salts are used in a wide variety of legitimate purposes - eg thermometers, paint. Symptoms and fatal doses vary immensely from type to type. Phosphorus Used to be used in matches and rat poison, but no longer.
Yellow phosphorus causes liver damage, delirium then coma.
Thallium A heavy metal. Salts are colourless, tasteless and easily dissolved in water. Symptoms easily confused with flu. Most distinstive one is hair loss. Fungi Not usually used as murder weapon.