With Atmospheric Moisture

Sesquiselenides with M = Pr, Nd, Sm decompose in moistair after a long time with liberation of H2Se, Obolonchik, Mikhlina [3, 7]. Slow liberation of red Se from material not kept in a dry glove box to avoid reaction with atmospheric moisture was observed by Guittard et al. [1]. Signs of decomposition had earlier been found after a few days, Klemm, Koczy [2]. 

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Polyurethane sealant formulations use TDI or MDI prepolymers made from polyether polyols. The sealants contain 30—50% of the prepolymer the remainder consists of pigments, fiUers, plastici2ers, adhesion promoters, and other additives. The curing of the sealant is conducted with atmospheric moisture. One-component windshield sealants utili2e diethyl malonate-blocked MDI prepolymers (46). Several polyurethane hybrid systems, containing epoxies, siUcones, or polysulfide, are also used. 

A solution of sulfur trioxide [7446-11-9] dissolved in chlorosulfonic acid [7990-94-5] CISO H, has been used as a smoke (U.S. designation FS) but it is not a U.S. standard agent (see Chlorosulfuric acid Sulfuric acid and sulfur trioxide). When FS is atomized in air, the sulfur trioxide evaporates from the small droplets and reacts with atmospheric moisture to form sulfuric acid vapor. This vapor condenses into minute droplets that form a dense white cloud. FS produces its effect almost instantaneously upon mechanical atomization into the atmosphere, except at very low temperatures. At such temperatures, the small amount of moisture normally present in the atmosphere, requires that FS be thermally generated with the addition of steam to be effective. FS can be used as a fill for artillery and mortar shells and bombs and can be effectively dispersed from low performance aircraft spray tanks. FS is both corrosive and toxic in the presence of moisture, which imposes limitations on its storage, handling, and use. 

Most polymers are very good electrical insulating materials because of their chemical composition, i.e., their electrical conductivity is exceptionally low. Because of this important property, many plastics are used to produce electrically nonconductive parts. However, the high surface resistance leads to an unwanted property the material is prone to electrostatic charge accumulation. To facilitate dissipation of the charge, antistatic agents are incorporated, which combine with atmospheric moisture on the plastic surface to form a conductive film. 

The first product slowly reacts with atmospheric moisture to give an unidentified white product and Cd metal. At low AsFj Cd ratios a brown product, Cd4(AsF6)2. is formed ... 

An important reaction of silicon compounds containing electronegative substituents, such as the halogens or a Group 15 or 16 element, is hydrolysis, which often occurs very readily even with atmospheric moisture. The primary reaction in silicone production is the hydrolysis of halosilanes, usually the readily available chlorosilanes, to give silanols, which then undergo acid-catalyzed condensation with loss of water, as shown in Scheme 1. 

The flammability and explosive hazard of ferrosilicon powder is increased substantially during grinding in a vibratory mill [1], Explosion hazards from air-hydrogen,—acetylene, or—propane mixtures formed during preparation of ferrosilicon containing alkaline earth additives are attributed to contact of barium or magnesium carbide or silicide additive with atmospheric moisture [2],... 

Mixtures of magnesium (or aluminium) powder with water can be caused to explode powerfully by initiation with a boosted detonator [1], The use of organic coatings on magnesium or aluminium powder in pyrotechnic compositions prevents reaction with atmospheric moisture and problems resulting from hydrogen evolution [2],... 

Bentzinger, von R. et al Praxis Naturwiss. Chem., 1987, 36, 38 A priming mixture of magnesium powder and barium peroxide to ignite thermite mixture was to be prepared, but as no barium peroxide was available, sodium peroxide was used instead. Some time after preparation, the mixture ignited spontaneously, because sodium peroxide, unlike barium peroxide, is very hygroscopic and forms hot cone, hydrogen peroxide from contact with atmospheric moisture. See Carbon dioxide, etc., above... 

Commercially available Modem KF-Titrators are usually equipped with specifically designed titration vessels that are exclusively meant to check and prevent the contact with atmospheric moisture. Quite a few such devices are armed with microprocessors that will perform the requisite operations sequentially in a programmed manner automatically and may also dish out a print-out of the desired results including the percentage moisture content. In fact, these Modem KF-Titrators not only afford greater accuracy and precision in results but also offer much ease and convenience in routine analysis as compared to the classical techniques based on either caulometry or controlled current potentiometiy using two indicator electrodes. 

Boron trifluoride combines with atmospheric moisture to form a white mist containing hydration and hydrolysis products. The odor is detectable at 3.0ppm, but this does not serve as an adequate warning. ... 

Cyanoacrylate adhesives, the famous consumer Super glue , is a monomer that polymerizes when it comes in contact with moisture, even with atmospheric moisture. 

As N,N-diethyl-l,2,2-trichlorovinylamine reacts rapidly with atmospheric moisture, it should be stored under nitrogen, preferably in a refrigerator. 

Interestingly, titanium tetrachloride is the ink" used by skywriters. When the pilot is ready to maneuver the airplane to spell out words, he or she releases a spray of TiCl4, which reacts with atmospheric moisture to form visibly white titanium dioxide particles. 

The product obtained by (III) is hygroscopic and water-soluble, in contrast to the material from (I) and (II). it is light violet in color, and it must be kept out of contact with atmospheric moisture. 

Beryllium chloride, [CAS 7787-47-5], BeCF, with a melting point of 440 C, is used as a component of molten salt baths for electrowinning or electrorefining of the metal. The compound hydrolyzes readily with atmospheric moisture, evolving HO, so protective atmospheres are required during processing. 

In terms of disadvantages, most inorganic molten salts are liquid at temperatures considerably above room temperature, necessitating that provisions be made for heating and thermostatting the electrochemical cell. Many exhibit rather limited electrochemical windows. In addition, some melts are corrosive to the usual cell and electrode materials and reactive with atmospheric moisture. The former attribute... 

Chien 6) has pointed out that doping not only stabilizes polyacetylene towards oxidation but also stabilizes the dopant. The most obvious example is AsF5, which reacts violently with atmospheric moisture but is stabilized in polyacetylene as the AsF6" counter-ion. 

The principal use for the tetrachloride is in pyrots as a smoke agent (called FM ), Ref 5 reports that the tetrachloride. . is extremely reactive resulting in the formation of hydrated oxides, or with atmospheric moisture and, when used for screening, is often disseminated from aircraft spray tanks. Its reaction with water vapor is relatively complex. First, the titanium tetrachloride is hydrated. This reaction is followed by further hydrolysis yielding, finally, titanium hydroxide and HC1. The smoke consists of a mixture of fine particles of solid titanium hydroxide, Ti(0H)4 the hydrated oxide, Ti02-H20 intermediate hydroxychlorides of titanium and dilute HC1 droplets. The sequence of reaction is ... 

Benzylmercapto-5-methoxycarbonyl-6//-l,3-thiazine (177) slowly hydrates with atmospheric moisture which leads, after elimination of benzyl mercaptan, to the 3,6-dihydro-2//-l,3-thiazine-2-one (178) (Scheme 70)... 

After preparation, all pure products should be stored in suitable clearly and permanently labelled containers. The bulk samples of stable solids and liquids may be stored in screw-capped and ground glass stoppered bottles respectively. Hygroscopic samples, or those liable to decomposition by contact with atmospheric moisture, should either be stored in a desiccator or in a bottle which is sealed by painting over the closure with molten paraffin wax. Where there is a possibility of photochemical decomposition of chemicals it is general good practice to keep them out of direct sunlight and to store them in brown bottles. 

This reagent may be purchased in the form of small pellets which are easily and quickly crushed in a mortar immediately before addition to the reaction flask (as for example in a Friedel-Crafts reaction, Expt 6.5), and covered with solvent. In these cases the small amount of hydrolysis which occurs during the grinding operation is not unduly harmful to the reaction yield. This pelleted material does unfortunately deteriorate fairly rapidly on reaction with atmospheric moisture on continued opening and closing of the reagent bottle. The material should therefore be carefully inspected before use and if a large amount of powdery white material is present a fresh bottle should be used. 

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