Sciencemadness Discussion Board

Manganese dioxide flammable?

Foeskes - 13-9-2017 at 04:25

Apparently manganese dioxide is flammable? According to Wikipedia it has a flash point of 535 C, which is when it decomposes.

woelen - 13-9-2017 at 04:35

It is not flammable. If the wiki page says so, then that page is in error.

It can support or intensify certain types of fire though. It is an oxidizer.

[Edited on 13-9-17 by woelen]

symboom - 13-9-2017 at 20:09

Tin(II) oxide burns in air with a dim green flame to form SnO2.

2 SnO + O2 → 2 SnO2

Reminds me of wikipedia tin 2 oxide

vmelkon - 25-9-2017 at 16:55

Flammable means something combines with oxygen and produces a plasma (fire) and the end product are gases.

Flash point means that a liquid or gas (probably a gas) is hot enough to spontaneously burn.
MnO2 doesn't have a flash point. It isn't flammable. I looked at the wikipedia page. That's just stupid.

VSEPR_VOID - 25-9-2017 at 19:05

Generally ionic compounds are not flammable

Metacelsus - 25-9-2017 at 19:13

Strictly speaking, that is true, since flammable refers to liquids with flash point below 100 °F (at least according to the NFPA), and most ionic compounds are solids at room temperature.

(Combustible refers to solids.)

However, many ionic compounds will burn. Examples: KH, FeS2, LiAlH4, CaC2, NaNH2, Hg(SCN)2, tetraethylammonium chloride

[Edited on 9-26-2017 by Metacelsus]

Deathunter88 - 26-9-2017 at 11:44

Quote: Originally posted by vmelkon  
Flammable means something combines with oxygen and produces a plasma (fire) and the end product are gases.

Flash point means that a liquid or gas (probably a gas) is hot enough to spontaneously burn.
MnO2 doesn't have a flash point. It isn't flammable. I looked at the wikipedia page. That's just stupid.


What you said about flash point isn't technically correct. Flash point is the temperature in which the solid or liquid gives off enough vapor in a container to create a brief "flash" when ignited. The flame point is the temperature where the solid or liquid gives off enough vapor to sustain a continued flame (this is usually just a bit higher than the flash point). What you are talking about is the autoignition temperature, the temperature at which a fuel/air mixture of the substance will spontaneously ignite without a direct ignition source. This is not at all correlated with the flash point or the flame point. For example, gasoline has a very low flash point but a high autoignition temperature, hence the need for spark plugs. Diesel on the other hand has a high flash point but a low autoignition temperature, which is why diesel engines have no spark plugs.

Deathunter88 - 26-9-2017 at 11:55

Quote: Originally posted by Metacelsus  
Strictly speaking, that is true, since flammable refers to liquids with flash point below 100 °F (at least according to the NFPA), and most ionic compounds are solids at room temperature.

(Combustible refers to solids.)

However, many ionic compounds will burn. Examples: KH, FeS2, LiAlH4, CaC2, NaNH2, Hg(SCN)2, tetraethylammonium chloride

[Edited on 9-26-2017 by Metacelsus]


Your definition of combustible is incorrect. Back when chemicals were labeled according to OSHA regulations, a flammable liquid is a liquid with a flash point below 37.8 degrees celsius, while a combustable liquid is a liquid with a flash point above 37.8 degrees celsius. However, with the introduction of the globally harmonized system for classification of chemicals (GHS), liquids are now classed into 4 separate categories.

Danger! Extremely flammable liquid and vapor: Flash point < 73°F(23°C) and initial boiling point < 95°F(35°C)
Cat. 1

Danger! Highly flammable liquid and vapor: Flash point < 73°F(23°C) and initial boiling point > 95°F(35°C)
Cat. 2

Warning! Flammable liquid and vapor: Flash point ≥ 73°F(23°C) and < 140°F(60.5°C)
Cat. 3

Warning! Combustable liquid: Flash point > 140°F(60.5°C) and < 199.4°F(93°C)
Cat. 4

Please do your best to familiarize yourself with these definitions, nothing make me more angry than someone calling diesel "flammable" or ethanol "combustable"!