Surface dust definition

Riesenfeld and Bohnholtzer and Riesenfeld and Schumacher used ozone concentrated by liquefaction and distillation. From their kinetic measurements they conclude that a reaction of the second order and one of the first order take place simultaneously at quite low pressures, 6-60 mm. Hg the first order reaction predominates. The velocity constants of the second order reaction are not influenced by the total pressure, while those of the first order reaction appear to be inversely proportional to the total pressure. The figures given show that the first order reaction at the lower pressures is considerably influenced by the surface, and is quite probably a heterogeneous reaction, though the authors themselves do not consider this to be definitely shown. The decomposition appears to be rather sensitive to catalysts such as dust particles. 

Detergency is about the theory and practice of the removal of foreign material from solids by surface-active substances. This definition excludes pure mechanical cleaning. Also a pure chemical cleaning, e.g., by solvation of the foreign material, is not considered. In textiles oily substances usually attach to the fibres (animal fats, fatty acids, hydrocarbons, etc.). Also dust, soot, and other solid particles have to be removed in a washing process. In order to test the effectiveness of a surfactant, textiles are often polluted with standard dirt mixtures and cleaned with a standard washing procedure (launderometer). Often cleanliness is measured on the basis of optical reflectivity of white textiles. 

Solid bodies of extraterrestrial material that penetrate the atmosphere and reach the Earth s surface are called meteorites. Other extraterrestrial materials include micrometer-sized interplanetary dust particles (IDEs) collected in the lower stratosphere and polar ices. Most meteorites and IDEs are fragments of asteroids, but some IDEs may represent cometary material and some meteorites are fragments of the planets Mars and Earth s moon. Meteorites recovered following observed falls are called/a// those which cannot definitely be associated with observed falls are called finds. Meteorites are given names based on the location where they were recovered (e.g., the Allende meteorite fell in Allende, Mexico). Meteorites recovered in Antarctica and the deserts of Australia and northern Africa are given names and numbers, because numerous samples are found in the same locations. Fragments thought to be of the same meteorite fall, which, in Antarctica or hot deserts, may have different numbers or even names because they were found in different locations, are called... 

Many expressions are used in connection with drying (e.g., dust-free, tack-free, surface-dry, dry-to-touch, dry-to-handle, dry-through, dry-to-recoat) but these terms do not have accurate definitions. However, equipment is available for measuring drying times in the laboratory under defined temperature and humidity conditions (Fig. 9.6). Internationally standardized test methods also exist ... 

In a patent of 1926, G. Shimadzu described an adaptation of the ball-mill process used for grinding ores, pigments, etc., by using lead balls tumbling against one another in a mill. The friction created sufficient heat to oxidise the outside surface of the lead balls and the obtained oxide layer fell off continuously in the form of dust. An air flow of a definite speed and humidity carries away the oxide dust through inbuilt screens to separate the coarser fractions and return them to the mill. The fine lead oxide particles were collected in storage silos. 

CAS 112945-52-5 EINECS/ELINCS 231-545-4 Synonyms Amorphous silica dust Cl 77711 Colloidal silica Colloidal silicon dioxide Eossil flour Eumed silica Fumed silicon dioxide Pigment white 27 Silica, amorphous Silica, amorphous fumed Silica, pyrogenic Silicic anhydride Silicon dioxide Definition High surface area aggregate particles of silica, with min. 89.5% SiOj content Empirical OjSi Formula SiOj... 

These definitions, which are used in application to dust deposits throughout most of this book, deviate from conventional terminology in that the term monolayer here implies less than full surface coverage, and layer implies either a multilayer or a single close-packed layer. (Translator s note.)... 

The relationship to the more well-known Zones 0, 1 and 2 is clear. However, the new definitions do not relate to layers or accumulations of dust, which must be avoided or, where they cannot be avoided, the surface temperature of equipment must be reduced to a safe level. 

The particle size distribution of a given dust or mist can be reported as a number, length, surface, volume or mass (weight) distribution. Figure 2.3.3 shows number and volume distribution curves for a sample powder. The curves in the figure are density curves the function values /(x) represent the fraction of particles in a given interval divided by the width of that interval. The definition of the number density distribution fN x) is thus ... 

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