Sublimation hazards

The metal is very effective as a sound absorber, is used as a radiation shield around X-ray equipment and nuclear reactors, and is used to absorb vibration. White lead, the basic carbonate, sublimed white lead, chrome yellow, and other lead compounds are used extensively in paints, although in recent years the use of lead in paints has been drastically curtailed to eliminate or reduce health hazards. 

Most tanks store Hquid rather than gases or soHds. Characteristics and properties such as corrosiveness, internal pressures of multicomponent solutions, tendency to scale or sublime, and formation of deposits and sludges are vital for the tank designer and the operator of the tank and are discussed herein. Excluded from the discussion are the unique properties and hazards of aerosols (qv), unstable Hquids, and emulsions (qv). A good source of information for Hquid properties for a wide range of compounds is available (2). 

Fire Hazards - Flash Point Not flammable Flammable Limits in Air (%) Not flammable Fire Extinguishing Agents Not pertinent Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products This product sublimes and forms toxic vapors when heated in flres Behavior in Fire Not pertinent Ignition Temperature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

Quenching the vapour with cold air in the chamber may increase the rate of heat removal although excessive nucleation is likely and the product crystals will be very small. Condenser walls may be kept free of solid by using internal scrapers, brushes, and other devices, and all vapour lines in sublimation units should be of large diameter, be adequately insulated, and if necessary, be provided with supplementary heating to minimise blockage due to the buildup of sublimate. One of the main hazards of air-entrainment sublimation is the risk of explosion since many solids that are considered safe in their normal state can form explosive mixtures with air. All electrical equipment should therefore be flame-proof, and all parts of the plant should be efficiently earthed to avoid build-up of static electricity. 

The use of sulfur as a fuel in pyrotechnic compositions dates back over one thousand years, and the material remains a widely-used component in black powder, colored smoke mixtures, and fireworks compositions. For pyrotechnic purposes, the material termed "flour of sulfur" that has been crystallized from molten sulfur is preferred. Sulfur purified by sublimation - termed "flowers of sulfur" - often contains significant amounts of oxidized, acidic impurities and can be quite hazardous in high-energy mixtures, especially those containing a chlorate oxidizer [11]. 

Arsenic. As, at wt 74.91 exists in three modifications all corresponding to the formula As4i mw 299.64. The most common form is the crystalline or a-form, known also as metallic arsenic. Its mp is 814° at 36 atm press, sublimation point 615, d 5 = 72 at RT (5.6-5.9 for commercial grade) and hardness 3.5 Mohs. Prepn props are given in Refs 1-6 toxicity, fire expln hazards of As dust are discussed in Ref 7. Arsenic is used in some alloys and for hardening lead shot... 

Condensers usually are large air-cooled chambers whose walls are kept clear with brushes or scrapers or even swinging weights. Scraped or brushed surface crystallizers such as Figure 16.10(a) should have some application as condensers. When a large rate of entrainer gas is employed, a subsequent collecting chamber will be needed. One of the hazards of entrainer sublimation with air is the possibility of explosions even of substances that are considered safe in their normal states. 

Barbier synthesis of 1-phenylethanol [54] Dry benzene (12 ml) (HAZARD), dry THF (3 ml) and magnesium (high purity, preferably sublimed) are placed in a dry reaction vessel fitted with a reflux condenser and a dropping funnel and furnished with an atmosphere of argon. The Barbier mixture , consisting of freshly distilled benzaldehyde (5.3 g),... 

The answer lies mainly in their distribution and properties. Elemental (liquid) mercury is volatile and can be inhaled. If sufficient of it enters the body, it is able to enter tissues such as the brain and cause damage, giving rise to headaches and also damaging the gums and teeth, for example. Liquid mercury, if taken into the stomach (which could occur if a child chewed and broke a thermometer, for example), would not be especially hazardous as the metal would be eliminated from the intestines in due course in the faeces. Little would be absorbed into the bloodstream. Inorganic mercury, such as occurs in salts (for example, mercuric chloride, also known as corrosive sublimate), can be absorbed from the gut and sufficient enters the bloodstream to bind to sulphur-containing... 

Firsich, D. W. (1984). Energetic material separations and specific polymorph preparation via thermal gradient sublimation. J. Hazard. Mater., 9, 133-7. [294]... 

---