Sciencemadness Discussion Board

NFPA-704: water is not reactive at all ?

metalresearcher - 14-10-2017 at 03:42

Each page of a chemical on world's largest online chemistry textbook has a datasheet on the top right of the page. So the page for water.
https://en.wikipedia.org/wiki/H2O
It shows an 'empty' (all zeroes) NFPA-704 blue-red-yellow diamond with no toxicity (blue, correct), no flammability (red, correct) and no reactivity (yellow).
But water is rather reactive with many chemicals, it corrodes many metals. I would guess it a value of 2 out of 4 (4 = highest NFPA rating).
I would only give noble gases, gold or WC or BN a zero rating for reactivity.

What are your opinions ?

[Edited on 2017-10-14 by metalresearcher]

crystal grower - 14-10-2017 at 03:58

This is the definition of reactivity value 0:
"Normally stable, even under fire exposure conditions, and is not reactive with water (e.g. helium, N2)."
I think it should be more specific. What is meant by normally stable? And also water reacts with water to some extent making H3O+ and OH- ions, doesn't it?

But looking at the definition of reactivity value 1:
"Normally stable, but can become unstable at elevated temperatures and pressures (e.g. propane)."
You can't really put water there.

So it seems value 0 is still the best one for water Deciding by these definitions.

Deathunter88 - 14-10-2017 at 05:49

Quote: Originally posted by metalresearcher  
Each page of a chemical on world's largest online chemistry textbook has a datasheet on the top right of the page. So the page for water.
https://en.wikipedia.org/wiki/H2O
It shows an 'empty' (all zeroes) NFPA-704 blue-red-yellow diamond with no toxicity (blue, correct), no flammability (red, correct) and no reactivity (yellow).
But water is rather reactive with many chemicals, it corrodes many metals. I would guess it a value of 2 out of 4 (4 = highest NFPA rating).
I would only give noble gases, gold or WC or BN a zero rating for reactivity.

What are your opinions ?

[Edited on 2017-10-14 by metalresearcher]


This thread belongs in detris IMO, since the poster did not seem to have done any background research on the issue. The NFPA is not a general guideline for chemicals, rather its a quick way for firefighters to see what hazards might exist. Would water be hazardous under fire conditions? I don't think so.

metalresearcher - 14-10-2017 at 09:05

Quote: Originally posted by Deathunter88  

Would water be hazardous under fire conditions? I don't think so.

In most cases, no. But in a magnesium fire ? Then the reactivity of water can be very dangerous. That is why powder, CO2, or halon extinguishers exist.

stygian - 14-10-2017 at 13:32

That's why you look at the info for magnesium (the fire youre fighting). Not water