Pyrophoric substance

This chapter will deal with a few additional spontaneously igniting substances. They act in this manner in what might be called their natural state or, more often, in a special condition of dispersion or preparation. 

That moisture in the air or in the oxygen plays some part in these oxidations is evident according to Holt and Sims from the fact that sodium or potassium can be distilled under oxygen that has been dried. with phosphorus pentoxide. Moreover, the burning metals are said to have their flame extinguished when immersed in thoroughly dried oxygen. 

However, this theory does not explain the existence of pyrophoric iron or the phenomenon of pyrophoricity at all, as shown in Table 2 by a conparison of the ratio of volume of oxide to volume of clement. Also, in analyzing the problem of autoxidation of the alkali metals, one must consider than quite different types of oxides result from burning of these metals in air, e.g. LijO, NajOj, KOj, RbOj, and CsOg. 

Sodium and potassium form alloys, among them a eutectic of 12.3°C (9.95°F) freezing point with 11.ly potassium This liquid alloy, perhaps because of its quickly renewable surface area, is spontaneously ignitible, especially if dropped from a few feet onto a wooden surface. 

The reactivity in air of the alkali metals is more or less preserved in their previously-described hydrides and also in a few little known compounds such as their silicides (W. Klemm 1948). Brauer describes the preparation of these compounds and characterizes them as follows NaSi, self-flammable as loose powder KSi puffs and flames in air with water, all four (i.e. the silicides of Na, K, Rb, Cs) ignite 

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PYROPHORIC SUBSTANCE A material that undergoes such vigorous oxidation or hydrolysis (often with evolution of highly-flammable gases) when exposed to atmospheric oxygen or to water, that it rapidly ignites without an external source of ignition. This is a special case of spontaneous combustion. 

Spontaneously Combustible and Pyrophoric Substances Spontaneously combustible substances will readily react with the oxygen in the atmosphere, igniting and burning even without an ignition source. Ignition may be immediate, or may result from a self-heating process that may take minutes or hours (hence, some spontaneously combustible substances are known as self-heating materials). 

Pyrophoric and other spontaneously combustible substances will generally be identified as such on their product literature, material safety data sheets (MSDSs), or International Chemical Safety Cards (ICSCs). If transported, these substances should be identified as DOT/UN Hazard Class 4.2 materials for shipping purposes and labeled as spontaneously combustible. For pyrophoric substances, the NFPA 704 diamond for container or vessel labeling has a red (top) quadrant with a rating of 4, indicating the highest severity of flammability hazard (NFPA 704, 2001). Note that pyrophoric materials often exhibit one or more other reactivity hazards as well, such as water reactivity. 

Misch metal, an alloy of cerium with other lanthanides is a pyrophoric substance and is used to make gas lighters and ignition devices. Some other applications of the metal or its alloys are in solid state devices rocket propellant compositions as getter in vacuum tubes and as a diluent for plutonium in nuclear fuel. 

Silanes are pyrophoric substances igniting and exploding spontaneously in air. They also liberate toxic hydrogen chloride gas. The gaseous monosilane and the vapors of higher silanes are irritants to the respiratory tract. Chronic exposure to low concentration can cause pulmonary edema. 

Ignition lag times of pyrophoric substances such as A1(BH4)3, AlMe3, BEt3, etc were found to increase (except for BEt3) with decreasing humidity. In fact, A1(BH4)3 is not pyrophoric in dry air (Ref 4)... 

Caution. Trimethylphosphine is a toxic, pyrophoric substance and should be used in an efficient fume hood. It should be destroyed by reaction with bleach. 

Pyrophoric substances that catch fire spontaneously in air without an ignition source. 

Self-heating substance means a solid or liquid substance, other than a pyrophoric substance, which, by reaction with air and without energy supply, is liable to self-heat this substance differs from a pyrophoric substance in that it will ignite only when in large amounts (kilograms) and after long periods of time (hours or days) ... 

Materials that will ignite spontaneously. Exmples of pyrophoric substances in air white phosphorus, alcyl derivates of aluminium or zinc or finely devided metals, which are readily oxidizers. 

These compounds are all essentially ionic and are not soluble to any appreciable extent in hydrocarbons they are exceedingly reactive, being sensitive to air and hydrolyzed vigorously by water. Although alkyl- and particularly aryl-sodium derivatives can be prepared for use as reaction intermediates in situ, they are seldom isolated. However, methylpotassium, which is a highly pyrophoric substance, has been obtained by the reaction ... 

A phosphorus-to-carbon triple bond evidently occurs in HC=P, which is a pyrophoric substance that polymerizes slowly even at —130°. The C==P bond length is only 1.54 A.62... 

Triethylborane is a pyrophoric substance, igniting spontaneonsly on exposure to air, chlorine, or bromine. Explosion may result when mixed with oxygen. Contact with ozone, peroxides and other oxidants can cause explosion. Its concentrated solutions can be pyrophoric. Flash point of 1 M solution in hexane is —23°C (—9°F), while that in tetrahydrofuran is —17°C (1°F) (Aldrich 1996). It decomposes explosively when mixed with water. 

L) Explosive substance or article containing an explosive substance and presenting a special risk (e. g., due to water activation or the presence of hypergolic liquids, phosphides, or a pyrophoric substance) necessitating isolation of each type. 

Pyrophoric substances, which are substances, including mixtures and solutions (liquid or solid) which even in small quantities ignite on contact with air within five minutes. These Class 4.2 substances are the most liable to spontaneous combustion. 

Articles, Pyrophoric Articles which contain a pyrophoric substance (capable of spontaneous ignition when exposed to air) and an explosive substance or component. The term excludes articles containing white phosphorus. UN App. B, ICAO A2, US 173.59, lATA App. A... 

This class comprises . 1 pyrophoric substances and. 2 self-heating substances. IMO Class 4.2,... 

The following types of substances are classified in Division 4.2 a) pyrophoric substances and b) self-heating substances. ICAO 2-4.2.1... 

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