Pyrophoric Properties

Very rudimentary test have been described to study whether or not a material is pyrophoric [134,135]. In general, the tests involve a procedure in which 1 to 2 cm3 of powder or 5 cm3 of liquid is poured from a height of about 1 m onto a noncombustible surface. Observations are made as to whether or not the substance ignites during dropping (powders) or within 5 minutes (all substances). The test is repeated six times. 

In another test with liquids, 0.5 cm3 is delivered from a syringe onto dry filter paper, and observations are made to see if ignition or charring occurs on the paper within 5 minutes. This test is repeated three times unless a positive reaction is observed earlier. 

When a substance ignites in one of the tests, or, with liquids, chars the filter paper in a test, the substance is considered to be pyrophoric. 

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Zirconium. While almost any metal in the finely divided state exhibits pyrophoric properties, a few metals when abraded emit a shower of sparks of sufficient temp to ignite hydrocarbon vapors. Cerium is the best known metal of this kind for commercial purposes, such as gas lighter flints. For military purposes Zr is the most used. It has found applications in HE and armor-piercing incendiary ammo, the lining of shaped-charge rounds, and in incendiary cluster bombs (Ref 7, pp 100-01)... 

Several tests have been developed to identify the hazards of reactive substances [10]. Test methods for determining pyrophoric properties, water reactivity, and oxidizing properties (Box 17) are discussed in Section 2.3.4. 

The Pd-C catalyst was then removed by filtration through Celite in a sintered glass funnel with the aid of a water aspirator. The filtration was completed by rinsing the packing with 95% ethanol (75 mL). Attention due to the pyrophoric properties of hydrogen-saturated palladium, it is important to keep the filter plug under a layer of ethanol. 

The combustion of Zn powder in air has been investigated (Ref 18). Owing to the higher vapor pressure of Zn compared with that of Al, ignition temps for Zn are also lower. Complete combustion of Zn powder takes place above 980° whereas the ignition temp for Al powder under the same exptl conditions is 1765° with a combustion temp of 2160—2290°. The process of self-oxidation of Zn dust is stimulated by humidity and the presence of chlorides, whereas the composition of the metallic phase, and the specific surface of the Zn dust were shown to be of minor importance in determining the pyrophoric properties (Ref 19). For a discussion of... 

The importance of good housekeeping must be emphasized. Any accumulation of Zr dust or powder on work benches, floors or clothes of personnel must be removed promptly. The pyrophoric properties of Zr dust or powder requires the selection of either wet or dry methods of dust collection A limited amount of moisture can make Zr powder ignition sensitive, but attempts to collect the dust dry by suction or convection flow risk dust expins which are easily initiated by static discharge or spontaneous combustion. Because nitrogen will also react with Zr,... 

Isohexides exhibit excellent properties as plasticizers for polyvinyl alcohol polymers.2 Compounds obtained from isosorbide and trialkylaluminum proved to be highly active cocatalysts for polymerization of alkenes. Such derivatives, which were supposed to be oligomeric O-aluminum-isosorbides, are of glass-like appearance and exhibit pyrophoric properties.255 Isosorbide is a component of mixtures used for water-based pigment inks, having excellent dispersion stability, which is necessary for ink-jet printing.256 257... 

When the ratio of ferrous sulphate (FeSOJ to magnesium chloride (MgClj) is 0-76, the deposit shows pyrophoric properties, and these become more pronounced as the ratio increases to 1 25, after which they diminish and entirely... 

By substituting cerous chloride for magnesium chloride in the solution the pyrophoric nature of the deposit is not increased. Temperature has considerable influence, because in certain cases the deposit formed in the cold is not pyrophoric, whilst that produced at 60° C. exhibits pronounced pyrophoric properties. Analysis of these alloys always shows the presence of a small quantity of mag-nesium, generally between 0 4 and 0-5 per cent. 

Unfortunately, diethyl zinc is not a chemical with great "stability" to work with. Because of its pyrophoric properties, DEZ must be handled with great caution and subsequently cannot be operated within libraries. This will limit potential library users. 

Depleted uranium is an excellent metallic substrate for radiation shielding and for armor and ammunition by the military due to its density and pyrophoric properties. Furthermore, the unique ability of uranium-based ammunitions to sharpen themselves upon impact, allowing for deeper penetration of the ammunitions, also makes DU a better substrate for weapons of mass destruction. As such, it is not suprising that the use of DU in military applications is expected to grow. This increased use will no doubt be bolstered by recent scientific studies showing that DU exposure has relatively low adverse health effects, contrary... 

A number of patents refer to the use of sodium amalgam as a cheap low-temperature reducing agent. Glasser and Hampel (22) and Imperial Chemicals Industries (65) indicate how to use the amalgam. The main drawbacks of this method are the health hazard with hot mercury, the pyrophoric properties of the intermediary products, and the necessity of upgrading the amalgam before its use, by vacuum distillation and elimination of excess mercury. This proposition has been discussed in more detail elsewhere (42). 

Process residues can also develop pyrophoric properties over a period of time. Ferrous sulphide residues from iron/acid reductions can behave in this way. 

Between about 1780 and 1850 a variety of fire-making devices were invented. The pyrophoric properties of white phosphorus were utilised in the earliest form of matches, which consisted of strips of paper tipped with the element and sealed in glass tubes. When broken, the paper would catch fire. The first striking matches ( friction lights ) were invented by J. Walker of England in 1826, but these did not contain phosphorus. Shortly afterwards a great improvement was achieved by C. Sauria of France who incorporated white P in the formulation. 

These elements form homoleptic allyl complexes as well as alkenyl compounds with mixed coordination spheres. These compounds are also sensitive to air and proton containing solvents (Table 7.8). They decompose at low temperatures, for example, the compound [Ta(C3115)4] is stable only in saturated hydrocarbon solutions below 273 K. The complexes [Nb(allyl)4] and [Ta(allyl)4] are paramagnetic. The complex [V(C3H5)3] has pyrophoric properties. Halogen and cyclopentadienyl allyl complexes are more stable. In the compound [V(C3H5)cp2] the allyl forms a a bond to the central atom thus, it acts as an ligand. 

Reductions. Pd EnCat has been found to effect a wide range of hydrogenation reactions at catalytic loadings. This catalyst, which can be easily recovered and reused, displays none of the pyrophoric properties associated with the reduced form of the free palladium salt. ... 

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