As flux

The As (arsenic) concentration of seawater is controlled by input of rivers, sedimentation on the seafloor, weathering of the seafloor, exchange between atmosphere and seawater, volcanic gas input, and hydrothermal input. Previous studies on the geochemical cycle of As have not taken into account the hydrothermal flux of As. Therefore, hydrothermal flux of As from back-arc, island arc and midoceanic ridges to ocean is considered below. 

As concentrations of submarine and subaerial hydrothermal solutions are summarized in Table 3.5, which clearly shows that the As concentration of hydrothermal solutions from back-arc basins and from subaerial island arc are higher than those from midoceanic ridges. Many analytical data on As concentration of hot springs in subaerial island arc are available (Ellis and Mahon, 1977 Weissberg et al., 1981). These data clearly indicate high concentration of As in these hot springs. 

An experimental study at 350°C on the interaction between NaCl solution and graywacke which occurs widely in island arc geologic setting indicates that the final solution contains (0.6-0.7) ppm As (Bischoff et al., 1981). Analytical data on As concentration of hydrothermal solution at back-arc basins are few. Arsenic concentration of hydrothermal solution at Lau Basin is 6.0-8.2 ppm (Foquet et al., 1991). We can also estimate As concentration of hydrothermal solution based on the solubility data on orpiment and realgar because these As-bearing minerals are common in back-arc basin deposits (e.g., Okinawa Trough, Kuroko deposits). 

Based on the above data and argument, it is inferred that hydrothermal solution venting from back-arc basins contains appreciable amounts of As (1-5 ppm). 

Using 2.5 X 10 kg/m.y. as the ocean crustal production rate at back-arc basins (Kaiho and Saito, 1994), 1-10 as seawater/rock ratio, and 1-5 ppm As concentration, we can estimate hydrothermal As flux from back-arc basins to be (1.3-0.13) x 10 g As/m.y. 

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Ammonium Chloride. Most ammonium chloride [12125-02-9], NH Cl, is used as rice paddy fertilizer small amounts are used in dry cells and as fluxing agents (see Ammonium COMPOUNDS). 

Dluxstone is a pure form of limestone used as flux or purifier in metaHurgical furnaces. It can be high calcium, magnesian, or dolomitic, providing it contains at least 95% carbonate. 

Fluxing lime is lump or pebble quicklime used as flux in steel (qv) manufacture the term may also be appHed more broadly to include fluxing of nonferrous metals and glass (qv). It is a type of chemical lime. 

Spunbonded fabrics are effective filters in that they are layered stmctures of relatively fine fibers, the three-dimensional stmcture of which creates a torturous path. Even relatively thin spunbonded fabrics (eg, 0.2—0.25 mm) present a significant challenge to the passage of soil fines and are suitable for use in some filtration appHcations. The porosity of geotextile fabrics is classified by means of several procedures such as flux (volume flow/area per time) and equivalent opening size (EOS), which is a measure of the apparent pore size of the openings in the fabric. The flux measures the porosity to Hquid water, and the EOS measures the porosity to soHd particles of a known diameter. Literature is available on limitations of particular styles of fabrics within an apphcation (63). 

Various documents relate to the use of formulations containing trietban olamine as flux for a variety of metals (118,119), for solders (120), for soldering pastes (121,122), and for low corrosion solder pastes (123). 

Water flux is sometimes normalized according to the initial or pure water flux,/ as or as flux drop, defined by... 

In membrane separations, the product S Dj is referred to as the per-meabihty, p (kmoL/m s Pa). The rate of passage of material through a membrane is referred to as flux, with symbol J . Jj is equal to Ni in the equations given above. Generally Jj has the dimensions of velocity, m/s (more conveniently, Im/s), or conventionally as /m hr, gal/ft day, or ftVft day. For most apphcations, throughput is expressed in volumes instead of moles or mass. 

Figure 6 RHEED (upper) end reflection enisotropy (iower) trensients obtained by interrupting and resuming As flux during otherwise normai growth (001) GaAs at 1 semiconductor ML per 4.6 s. Data are shown for photon energies near the Ga RD peak at 2.5 eV (right) and minimum at 3.5 eV (ieft).

The residuum from vacuum distillation became, and still is, the basic component of residual fuel oil. It contains the heaviest fraction of the crude, including all the ash and asphaltenes. It is extremely high in viscosity and must be diluted with light distillate flux (a low viscosity distillate or residual fraction which is blended with a high viscosity residual fraction to yield a fuel in the desired viscosity range) to reach residual fuel viscosity. The lowest value distillates, usually cracked stocks, are used as flux. In some cases the vacuum residuum is visbroken to reduce its viscosity so that it requires less distillate flux. 

Catalyst films used in electrochemical promotion (NEMCA) studies are usually prepared by using commercial metal pastes. Unfluxed pastes should be used, as fluxes may introduce unwanted side reactions or block electrocatalytic and catalytic sites. This action may obscure or even totally inhibit the electrochemical promotion effect. 

In more specific studies of transport processes, flux is normally defined as the amoimt of material transferred per unit area per unit time. To distinguish between these two conflicting definitions, we refer to the latter as "flux density."... 

While metabolic engineers traditionally sought the rate-limiting enzyme to unlock flow through a pathway, now they understand that there may be many points of control and feedback with the metabolic network, and seek to empirically determine the dynamics of the interactions between rate controllers and other factors. For example, the sizes of metabolic precursor pools and the catabolism or sequestration of products affect accumulation as well as flux through the pathway. 

It seems unlikely that all of the oceanic crust produced interacts with seawater (Holland, 1978). Accepting that 30% of oceanic crust interacts with circulating seawater, hydrothermal As flux is estimated to be (3.8-0.1) x lO g As/year. This flux, although... 

The flux of volcanic gas to ocean has not been estimated. Walsh et al. (1979) estimated As flux of volcanic gas to atmosphere to be 2.8 x 10 g/year. Therefore, this flux to ocean is also small. 

Tin slags account for a sizeable fraction of the world s tantalum production. These slags are melted in electric arc furnaces, together with coke and lime (as flux), and this pyrometallurgical process leads to the production of synthetic niobium/tantalum concentrates. The waste products of this operation are mechanically separated slags which can be used, for instance, as landfill. The exhaust gases from this process are of minor consequence if dust is eliminated by the use of filters. 

The addition of a relatively small amount of such substances as soda, potash, or borax, all known as fluxes or fluxing materials, lowers the melting temperature of silica sand from over 1700°C to below 1000°C, a temperature feasible in ancient furnaces (see Textbox 28). 

Soda (composed of sodium oxide) and potash (composed of potassium oxide) are relatively easy to obtain or to make, work, and handle. Although they do not occur naturally, they could be quite easily prepared in the past by burning some plants (see Textbox 28). Both these oxides were used as fluxes for making early types of glass articles, particularly small vessels and decorative objects. 

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