Shock-sensitive chemicals

Does this operation involve the use, storage, or generation of peroxide-forming chemicals, shock-sensitive chemicals, or picric acid ... 

Stabilized lithium acetyhde is not pyrophoric or shock-sensitive as are the transition-metal acetyhdes. Among its uses are ethynylation of halogenated hydrocarbons to give long-chain acetylenes (132) and ethynylation of ketosteroids and other ketones in the pharmaceutical field to yield the respective ethynyl alcohols (133) (see Acetylene-derived chemicals). 

Reactive Chemicals Reviews The process chemistry is reviewed for evidence of exotherms, shock sensitivity, and other insta-bihty, with emphasis on possible exothermic reactions. It is especially important to consider pressure effects— Pressure blows up people, not temperature The pumose of this review is to prevent unexpected and uncontrolled chemical reactions. Reviewers should be knowledgeable people in the field of reactive chemicals and include people from loss prevention, manufacturing, and research. 

Review of reactive chemicals test data for evidence of flamma-bihty charac teristics, exotherms, shock sensitivity, and other evidence of instability... 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials May ignite combustible materials such as wood Stability During Transport Heat-and-shock-sensitive crystals may separate at very low temperature during transport Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

On long term storage, moisture can cause undesirable chem reactions such as the formation of nitric acid, which can react with such metals as Al, Mg, Fe, Cu, etc, to yield H2. The H2, in turn, in redox reactions with both metals and org chemicals present can form shock sensitive compds (Refs 6, 11, 12, 15, 17 26). 

An acidified solution of the sodium salt was allowed to evaporate during 3 days and spontaneously exploded 2 weeks later. The nature of the explosive species, possibly the aci-tetrazolic acid, was being sought [1]. The silver and mercury salts are explosive [2], The chemical properties of the free nitrotetrazole have been studied. The sodium salt tetrahydrate loses water above 50°C, greatly increasing its friction and shock sensitivity [3],... 

Decomposes on exposure to light. Large volumes of this chemical may be shock sensitive. When heated, this compound may decompose violently. 

Case histories regarding reactive chemicals teach the importance of understanding the reactive properties of chemicals before working with them. The best source of data is the open literature. If data are not available, experimental testing is necessary. Data of special interest include decomposition temperatures, rate of reaction or activation energy, impact shock sensitivity, and flash point. 

The decomposition of some materials into smaller, more stable molecules can be initiated by mechanical shock alone, and they are known as shock-sensitive. Many commercially important chemicals are thermally sensitive and decompose with the addition of heat. For storage situations, the critical temperature at which the thermal energy is sufficient to start an uncontrolled reaction in a particular storage configuration for a specified time is known as the self-accelerating decomposition temperature (SADT), as described in NFPA 49. 

Categories Polymerizing Shock sensitive Thermally decomposing Rearranging Examples Chemicals that by themselves are stable if they decompose when heated, decomposition is not self-accelerating... 

Chemical/Physical. Picric acid explodes when heated >300 °C (Weast, 1986). Shock sensitive (quoted, Keith and Walters, 1992). 

Nitroglycol (NGC) has similar physical and chemical properties to those of NG. However, its vapor pressure is too high to permit its use as a major component of propellants and explosives. NGG is used as an additive to reduce the freezing temperature of NG and to formulate explosives. However, the shock-sensitivity of the resulting NG-based explosives is much higher than that of other types of explosives. 

Fluorine nitrate is shock sensitive, especially in liquid state. The liquefied material explodes when shaken vigorously or in contact with alcohol, ether, andine, or grease (Bretherick s Handbook of Reactive Chemical Hazards, 5th. Ed., P. Urhen (ed.) 1995, pp 1405-6, Oxford, UK Butterworth-Heinemann). The gas catches fire when mixed with ammonia or hydrogen sulfide. 

Lead azide explodes on heating at 350°C or on percussion. Its detonation velocity is 5.1 km/sec (Meyer, E. 1989. Chemistry of Hazardous Materials, 2nreaction with carbon disulfide and forms shock-sensitive copper and zinc azides when mixed with the solutions of copper and zinc salts (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, ed. New York John Wdey). 

Transition of combstn to deflgrn in expls. Combstn of powdered expls at high constant pressures) 11) J. Eadie, "The Effect of Wax on the Shock Sensitivity of Explosive Compacts , 4thONRSympDeton(l965), 399-403 12) J.E. Hay et al, "The Effect of Physical and Chemical Properties on the Sensitivity of Liquid Explosives , 4thONRSympDeton... 

The lower third of the chart (up to Tq-Tj = 1,000°K) contains hazardous explosives or materials with an NFPA rating of 3 or 4 (shock sensitive explosive materials). The single exception is hydrogen cyanide with an NFPA rating of 2 (unstable, capable of violent chemical change, but does not detonate)... 

Review the reactive chemicals test data summaries for exotherms, shock sensitivity or other indicators of instability or energy release potential. 

The ease of occurrence of explosion for a self-reactive chemical may be judged by its shock sensitivity and its ability to propagate the explosion. The shock sensitivity of highly sensitive chemicals can be measured by the drop ball test described above. However, those chemicals whose hazard can be measured by the drop ball test are too sensitive for daily use. Different methods are needed for those chemicals which are not likely to explode in daily use to determine whether a substance can cause explosion under extraordinary conditions. 

A shock sensitivity test using a Mklll ballistic mortar (Variable initiator test) has been developed for that purpose 2 0 . One can measure the ease of occurrence of explosions for chemicals with low sensitivity which fall on the boundary of explosives and nonexplosives. The method is place 5g of the test chemical into a 100kg mortar and initiate it with a detonator, which is equivalent to 0.2 - 2.0g of the high explosive PETN. 

Reactive hazard evaluations should be made on all new processes as well as existing processes on a periodic basis. There is no substitute for experience, good judgement, and good data when evaluating potential hazards. Reviews in process chemistry should include (a) reactions, (b) side reactions, (c) heat of reaction, (d) potential pressure buildup, and (e) intermediate streams. Reactive chemicals test data should be reviewed for evidence of flammability characteristics, exotherms, shock sensitivity, or other evidence of instability. Examine Planned operation of the process should be examined, especially for... 

---