[Drivingforfun]

Just wondered if anyone here happens to know the answer to a random question

I was reading about a few substances that exist which have an autoignition temperature (temperature at which they will spontaneously combust) very low, in some cases room temperature or below and have to be stored at very low temperatures

If one of these substances was put into a normal room and allowed to combust, would the flames be safe to touch?

[Mark07]

Originally Posted by Drivingforfun

If one of these substances was put into a normal room and allowed to combust, would the flames be safe to touch?

I have to say that I love this type of question.

I didn't know the answer and after some googling I'm still not sure. It looks like the answer is, in most cases, no.

As an example, white phosphorus can spontaneously combust at temperatures from 30C, but the flames will be hundreds (or thousands) of degrees.

Linking this back to motoring, I saw this on wikipedia about cool flames (400C)

"Cold flames are difficult to observe and are uncommon in everyday life, but they are responsible for engine knock– the undesirable, erratic, and noisy combustion of low-octane fuels in internal combustion engine"

I hope someone more knowledgeable can give a more detailed/better answer.

[Rolebama]

I was always taught/told that there is no such thing as a silly/stupid question - only stupid answers.
I remember at school playing with phosphor, and one of the kids lost a leg. It looked like sticks of chalk and was stored submerged in a glass bottle of water. As it dried. it spontaneously ignited, even in as much of a vacuum our old equipment could make. Anyway this kid stole a stick when he was told to put the bottle back away. He was on the bus with it in his pocket when it went off. It burnt through to the bone and the wound was too bad to save the leg. When the Science Master found out about it he pointed out that as it burns, it melts and becomes super sticky, hence the severity of the burn. All dealings with self-igniting chemicals and mixtures was promptly taken off the curriculum.

[NMNeil]

As Mark07 said, white phosphorus at 34C, add to that;
Silane at 21C and Triethylborane at -20C (Triethylborane was used to start the engines on the Lockheed SR-71 Blackbird for that very reason)
https://www.tayloredge.com/reference.../ignition.html

[brojonas]

Been reading about some crazy metals lately! It seems that zirconium, titanium and hafnium could explode in contact with air at room temperature. That's not the only danger though. I checked out a safety sheet (MSDS) for zirconium (https://nj.gov/health/eoh/rtkweb/documents/fs/2047.pdf) and it turns out inhaling it can mess with your lungs, and the powder can irritate your eyes. Sounds like repeated contact can even give you a skin reaction.