Explosion, liquid nitrogen

Accidental addition of liquid oxygen to vacuum jars containing acetone residues from trap-cooling use caused a violent explosion. Liquid nitrogen is less hazardous as a trap coolant, but only under controlled conditions. 

If liquids act as thermal sinks to desensitize explosives, liquid nitrogen might be presumed to maximize the effect. Tests using a Picatinny Arsenal apparatus modified with the addition of a holder for the nitrogen indicate that of the primaiy explosives tested only dextrinated lead azide displays a decrease in impact sensitivity (Table VIII) [57]. 

I do not know of any case in which delivery of liquid oxygen instead of liquid nitrogen caused an explosion. But, as stated in Section 12.3.1. in one case the nitrogen was used to inert a catalyst bed. and the catalyst got hot in another case a high-oxygen-concentration alarm in the plant sounded, and in several cases check analyses showed that oxygen had been supplied. 

The addition of solid Ba2Xe06 to cold cone H2SO4 produces the second known oxide of xenon, Xe04. This is an explosively unstable gas which may be condensed in a liquid nitrogen trap. The solid tends to detonate when melted but small sublimed crystals have been shown to melt sharply at —35.9°C. Xe04 has only been incompletely studied, but electron diffraction and infrared evidence show the molecule to be tetrahedral. 

A nitrobenzene/nitrogen tetroxide mixture used to be used as an explosive liquid. However, it is not still used due to its high sensitivity to thermal load. 

Like other substituted acetylenes, this is violently unstable. Attempts to prepare poly (difluoroacetylene) thence usually end in explosion [1], Difluoroacetylene decomposes slowly even at liquid nitrogen temperatures [2]. 

A terpene inhibitor is usually added to the monomer to prevent spontaneous polymerisation, and in its absence, the monomer will spontaneously explode at pressures above 2.7 bar. The inhibited monomer will explode if ignited [1]. Explosion under thermal initiation is now held to be a disproportionation, that to tetrafluo-romethane and carbon gives 3.2 kJ/g, the same energy as black powder [3], Liquid tetrafluoroethylene, being collected in a liquid nitrogen-cooled trap open to air, formed a peroxidic polymer which exploded [2]. 

Houseman, T. H. et al., J. Labelled Compd. Radiopharm., 1978, 14, 164 Liquid nitrogen should not be used as a trap coolant with acetylene, owing to the explosive nature of liquid or solid acetylene (title reference 5 above). 

A violent explosion occurred after distillation at 47-49°C/60-65 mbar [l],and also during distillation at 48-53°C/66 mbar use of solutions of undistilled material was recommended [2], The compound exploded on one occasion in the solid state after condensation at — 196°C, probably owing to fortuitous tribomechanical shock [3], A similar explosion on chilling a sample in liquid nitrogen had been noted previously [4], Of two simplified methods of isolating the material without distillation [4,5],... 

Use of liquid nitrogen in cryogenic grinding of fatty materials led to an explosion. Condensation of liquid oxygen onto the fatty material, with initiation by the grinding friction seems a likely causative sequence. 

Before thawing a frozen aqueous sample, allow a few seconds for condensed air to evaporate. Omitting the air eruption step and immediately putting the tube from the liquid nitrogen in the lukewarm water is very likely to lead to explosion of the tube due to rapid air expansion. 

Contact of the neat liquids with uncooled methanol is explosively violent and leads to ignition. For analysis, ampouled samples of dialkylzincs must first be frozen in liquid nitrogen before being broken under methanol-heptane mixtures at — 60°C. See Zinc ethoxide Nitric acid... 

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