A more interesting application is the use in atomic clocks which are accurate to 5 seconds in 300 years. Biological Role Caesium has no known biological role. It is non-toxic. General Information Caesium reacts rapidly with oxygen and explosively with water. The metal is characterised by a spectrum containing two bright lines in the blue along with several others in the red, yellow and green.
Caesium hydroxide is the strongest base known, and can attack glass.