Dissolutive wetting

1 Dissolution-insensitive Tlv ar,d °sl values. This case was studied by Warren et al. (1998) and Yost and O Toole (1998) and modelled by the first authors for a liquid metal B/solid metal A system in which, at the experimental 

Calculations by Warren et al. for the second stage are in semi-quantitative agreement with experimental results. For instance, the calculated value of R2/Ri at t = 300 s is 1.07, lower but of the same order of magnitude as the experimental value of 1.26. To sum up, dissolution in metal/metal systems increases the contact 

2 Dissolution sensitive oL y and oSL values. Much stronger increases in R are expected from dissolution of a tensio-active species able to decrease significantly Csl and/or TlV, even if the corresponding increase of the liquid volume is negligible. For example, for a droplet with 6y = 40°, a decrease of rLV of 30% is enough to increase the contact radius by a factor 2. 

Laurent (1988) studied the particular case where dissolution is high enough to modify tSl (or rLv) but small enough to allow neglect of any deviation of the S/L 

Assuming that the mobility of the triple line (expressed by the velocity of the line in the corresponding non-reactive system for the same instantaneous contact angle) is high compared to the rate of interfacial transfer and to the diffusion rate in the bulk liquid, capillary equilibrium at the triple line is readily maintained, so that fd(t) = 0 and the instantaneous contact angle is given by  

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Controlling fluid loss loss is particularly important in the case of the expensive high density brine completion fluids. While copolymers and terpolymers of vinyl monomers such as sodium poly(2-acrylamido-2-methylpropanesulfonate-co-N,N-dimethylacrylamide-coacrylic acid) has been used (H)), hydroxyethyl cellulose is the most commonly used fluid loss additive (11). It is difficult to get most polymers to hydrate in these brines (which may contain less than 50% wt. water). The treatment of HEC particle surfaces with aldehydes such as glyoxal can delay hydration until the HEC particles are well dispersed (12). Slurries in low viscosity oils (13) and alcohols have been used to disperse HEC particles prior to their addition to high density brines. This and the use of hot brines has been found to aid HEC dissolution. Wetting agents such as sulfosuccinate diesters have been found to result in increased permeability in cores invaded by high density brines (14). 

Figure 2.17. Two extreme cases of dissolutive wetting, (a) Dissolution of the solid modifies the geometry at the triple line, (b) A slight dissolution is enough to modify the surface energies of the system while the S/L interface remains macroscopically planar.

Air(l) Water (2) Diffusion Rain dissolution Wet deposition Dry Deposition Water (2) Air (1) Soil (3) Air(l) Soil (3) Water (2) Diffusion Diffusion Water run-off Soil erosion... 

At the end of xanthation, any remaining traces of CS2 are flushed from the wet churn prior to, or in some cases by, admitting a charge of the dissolving or mixer soda in order to commence dissolution. For a dry churn operation, the vessel is opened to allow the golden xanthate cmmbs to be discharged into a separate mixer. 

The formation of the metallic salts is a pyrometaHurgical process, and is commonly referred to as the dry process. The separation of the salts from each other is accompHshed by selective dissolution in water, and is named the wet process. 

Commercial condensed phosphoric acids are mixtures of linear polyphosphoric acids made by the thermal process either direcdy or as a by-product of heat recovery. Wet-process acid may also be concentrated to - 70% P2O5 by evaporation. Liaear phosphoric acids are strongly hygroscopic and undergo viscosity changes and hydrolysis to less complex forms when exposed to moist air. Upon dissolution ia excess water, hydrolytic degradation to phosphoric acid occurs the hydrolysis rate is highly temperature-dependent. At 25°C, the half-life for the formation of phosphoric acid from the condensed forms is several days, whereas at 100°C the half-life is a matter of minutes. 

Etch Mechanisms. Most wet etches for the compound semiconductors employ oxidation of the semiconductor followed by dissolution of the oxide. For this reason, many wet etches contain the oxidant hydrogen peroxide, although nitric acid can also be used. One advantage of wet etching over dry is the absence of subsurface damage that is common with dry etching. Metal contacts placed on wet-etched surfaces exhibit more ideal characteristics than dry-etched surfaces. 

Oxide Chlorides. Zirconium oxide dichloride, ZrOCl2 -8H2 0 [13520-92-8] commonly called zirconium oxychloride, is really a hydroxyl chloride, [Zr4(OH)g T6H2 0]Clg T2H2O (189). Zirconium oxychloride is produced commercially by caustic fusion of zircon, followed by water washing to remove sodium siUcate and to hydrolyze the sodium zirconate the wet filter pulp is dissolved in hot hydrochloric acid, and ZrOCl2 -8H2 O is recovered from the solution by crystallization. An aqueous solution is also produced by the dissolution and hydrolysis of zirconium tetrachloride in water, or by the addition of hydrochloric acid to zirconium carbonate. 

From wetted wall column and dissolution data— see Table 5-22-B. 

The polymeric latex obtained in a hydrophobic organic solvent is poorly dispersed in water because of the presence of an emulsifier with a low HLB value. For this reason, a wetting agent is added to water or emulsion prior to the dissolution. The wetting agent (a surface active substance with a high HLB value) facilitates the inversion of latex phases to produce a direct type emulsion. Usually, it belongs to oxyethylated alkylphenols, fatty alcohols, or fatty acids. 

After the initial growth, progesterone (05-5 g l"1) is added as a powder or as an acetone solution. If a powdered form is used, it is wetted with a small amount (0.01%) of Tween to facilitate its dissolution into the reaction mixture. A single addition of progesterone at a concentration of about 5g T1 enables about 86% hydroxylation to take place within about 50h. The remaining progesterone remains unaltered. 

Generally, wet chemical methods require the availability of compounds which are soluble in water or in another solvent. The dissolution in a solvent allows intimate mixture on an atomic or molecular scale. However, it has to be ensured that no compound precipitates before the others when the solvent is evaporated, or else insoluble products are formed. The importance of wet chemical methods lies in the possibility of simple upscaling to industrial needs. 

Adsorption of water on salt crystals plays a key role in many atmospheric and environmental processes. Alkah halides in particular play an important role in the first stages of drop growth in clouds. To understand the atomistic details of the wetting and dissolution processes that take place in these crystals, we apphed SPFM to the smdy of the adsorption of water vapor on single crystal surfaces and the role of surface defects, such as steps. 

In the fertilizer manufacturing scheme, the wet process phosphoric acid most commonly ensues from dissolution of sedimentary phosphate rock in sulfuric acid. Such acid solution contains around 1 g 1 1 uranium which is recovered as the byproduct. This task is accomplished by three well-proven extraction processes, some salient details of which are presented in Table 5.10. 

While most polymer/additive analysis procedures are based on solvent or heat extraction, dissolution/precipita-tion, digestions or nondestructive techniques generally suitable for various additive classes and polymer matrices, a few class-selective procedures have been described which are based on specific chemical reactions. These wet chemical techniques are to be considered as isolated cases with great specificity. 

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