What is the most dangerous chemical that you know about

[lajoswinkler]

I'd like to add silicon(IV) chloride on the list of worse things I know of. It hydrolizes to form silicon(IV) oxide and hydrogen chloride, fuming on air.

Imagine what would happen if the fume, still having some of the reactant, touched your eyes or your alveoli was exposed to it. Deposition of what's essentially sand, and hydrochloric acid. Extreme injuries to mucous membranes and pulmonary oedema.

[Hydrazine_Soup]

Pentaborane probably.

Edited March 5, 2020 by Hydrazine_Soup

[Hannu]

I know many extremely hazardous chemicals and do not think that it is sane to argue what of them are the most dangerous. It depends on circumstances and if somebody use them they obey very strict safety regulation. The most hazardous chemical I have used is hydrofluoric acid. It is nothing compared to extremities mentioned in this discussion but it is easy to achieve very painful death if you make stupid things with it. Other nasty things are organometallic compounds but I have just controlled their flows with computer controlled valves in secured pipelines. If there had been a leak, gas detectors would have alarmed and ventilation would have suck gases. I and everybody else would have left the building and properly equipped service team would have solved the problem.