Dissolution in water

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 production and utilization of ozone by silent electric discharge consists of five basic unit operations gas preparation, electrical power supply, ozone generation, contacting (ie, ozone dissolution in water), and destmction of ozone in contactor off-gases (Fig. 1). 

On dissolution in water, peroxohydrates Hberate hydrogen peroxide into solution. Some peroxo salts also Hberate hydrogen peroxide when dissolved in water, and before the introduction of x-ray crystallography, compounds within these classes were often confused with each other. 

Sodium hydroxide (NaOH) (caustic soda) White deliquescent solid. Sticks, flakes, pellets. Dissolution in water is highly exothermic. Strongly basic. Severe hazard to skin tissue... 

The brush phases are made from the mono-chlorsilanes or the mono-alkoxysilanes which attach a single organic moiety to each reacted hydroxyl group. For example using octyldimethylchlorsilane, dimethyloctyl chains would be attached to the surface like bristles of a brush, hence the term brush phase. In all bonding processes, some hydroxyl groups remain unreacted which would allow the polar character of the silica play a part in retention and also render the surface liable to dissolution in water and dilute acids. For this reason the material is capped by treatment with either trimethylchlorsilane or hexamethyldisilazane to eliminate any unreacted or stearically... 

In the case of water-soluble polymers, there is another factor that has to be taken into account when considering solubility, namely the possibility of hydrophobic interactions. If we consider a polymer, even one that is soluble in water, we notice that it is made up of two types of chemical species, the polar functional groups and the non-polar backbone. Typically, polymers have an organic backbone that consists of C—C chains with the majority of valence sites on the carbon atoms occupied by hydrogen atoms. In other words, this kind of polymer partially exhibits the nature of a hydrocarbon, and as such resists dissolution in water. 

On cooling (NH4)2S5 crystallizes as yellow to orange-yellow needles which melt at 95 °C in a sealed glass tube but decompose in air [reverse reaction at Eq. (17)] and on dissolution in water. (Et4N)2Ss is obtained by reaction of Et4NCl with Na2S5 in ethanol [33]. 

Sodium hydroxide (NaOH) (caustic soda) Potassium hydroxide (KOH) (caustic potash) Calcium hydroxide (Ca(OH)2) (slaked lime) Ammonium hydroxide (NH4OH) (aqueous ammonia solution) White deliquescent solid. Sticks, flakes, pellets. Dissolution in water is highly exothermic. Strongly basic. Severe hazard to skin tissue White deliquescent solid. Sticks, flakes, pellets. Dissolution In water is highly exothermic. Strongly basic. Severe hazard to skin tissue White powder soluble in water yielding lime water. Alkaline Weakly alkaline. Emits ammonia gas. Severe eye irritant... 

Good cements show little dissolution in water, less than 01 % using the standard test (see Chapter 10) the amount can be much greater for poorer examples. Dissolution represents the amount of material eluted from a one-hour-old cement as it ages in water for a further 24 hours. As the cement ages further the rate of dissolution falls although it always remains significant (Wilson, Kent Lewis, 1970 Wilson, 1976 de Freitas, 1973). 

Soon after inception of the theory of electrolytic dissociation, it was shown that two types of componnds exist that can dissociate upon dissolution in water (or other solvents) ... 

Kigoshi K (1971) Alpha recoil " Th dissolution in water and the " U/ U disequilibrium in nature. Science 173 47-48... 

Reaction (II) could be the neutralization of acetic acid by potassium hydroxide, yielding potassium acetate which can be isolated in the crystalline state. On dissolution in water the K+ cation is only hydrated in solution but does not participate in a protolytic reaction. In this way, the weak base CH3COO is quantitatively introduced into solution in the absence of an equilibrium amount of the conjugate weak acid CH3COOH. Thus... 

Since dosage forms contain more than just active drug, it is of practical interest to understand how the various components from a multicomponent solid influence their own dissolution and release. Nelson [18] was one of the first pharma-ceuticists to ponder this question and perform the initial dissolution studies. Unfortunately, Nelson initially considered the dissolution of interacting solids (benzoic acid + trisodium phosphate), which is a more complicated and more complex situation than simple multicomponent dissolution of noninteracting solids. Nelson did show that for his benzoic acid and trisodium phosphate pellets, there was a maximum increase in benzoic acid dissolution in water at a mole fraction ratio of 2 1 (benzoic acid trisodium phosphate) and that the benzoic acid dissolution rate associated with the maximum rate was some 40 times greater than that of benzoic acid alone. 

Carbon dioxide can change the pH of water because of its slightly dissolution in water to form carbonic acid, H2COs (a weak acid), according to Equation 9 ... 

The solubility profile for acetazolamide, after 24, 48 and 72 hours from dissolution in water at 25°C is shown in Fig. 17.4. Equilibrium is reached only after 72 hours from dissolution, and any solubility measurements made before that time may lead to major errors in solubility determination. Hence, it is unclear whether all the solubility data reported in the literature has been obtained with careful checking of such phenomena. 

That eh is the intermediate species and not the H atom has been verified by adding NzO and methanol to water then, N2, not H2, is the principal product. Alkali and alkaline earth metals above Na in the electrochemical series will also generate eh on dissolution in water. Moreover the H/D isotope effect in water containing 50% D is consistent with the reaction 2eh—H2 + 20H (Anbar and Meyerstein, 1966 Hart and Anbar, 1970). 

Enthalpies of solution of lanthanum (180) and scandium (208) trichlorides in 14.1% and in 0.5 M aqueous hydrochloric acid, respectively, are also smaller than the respective enthalpies of solution in water. In the former case the values - 26.4 and — 31.6 kcal mol-1 were measured at 20°C in the latter, a value of — 43.0 kcal mol-1 for dissolution in hydrochloric acid at 25°C has to be compared with a value of -47.1 kcal mol-1 for dissolution in water at 20°C (180). Enthalpies of... 

Round sodium chloride particles of 0.2 mm in diameter were prepared by rapid cooling of droplets of a NaCl melt175). Their heat of dissolution in water exceeded that of large crystals by about 0.3% only. Consequently, the precision of the Us values was low the results of 3 pairs of experiments ranged from 4000 to 30000 erg/cm2. This high range may have been caused by the fact that the minute spheres were far from internal equilibrium. 

Much emphasis has been placed on the selectivity of quaternary ammonium borohydrides in their reduction of aldehydes and ketones [18-20]. Predictably, steric factors are important, as are mesomeric electronic effects in the case of 4-substituted benzaldehydes. However, comparison of the relative merits of the use of tetraethyl-ammonium, or tetra-n-butylammonium borohydride in dichloromethane, and of sodium borohydride in isopropanol, has shown that, in the competitive reduction of benzaldehyde and acetophenone, each system preferentially reduces the aldehyde and that the ratio of benzyl alcohol to 1-phenylethanol is invariably ca. 4 1 [18-20], Thus, the only advantage in the use of the ammonium salts would appear to facilitate the use of non-hydroxylic solvents. In all reductions, the use of the more lipophilic tetra-n-butylammonium salt is to be preferred and the only advantage in using the tetraethylammonium salt is its ready removal from the reaction mixture by dissolution in water. 

Electric conductance measurements have been widely used in the study of lanthanide complexes to determine the nature of the anions in the complexes and hence to indicate the possible coordination number of the lanthanide ion. Water is a strong donor toward the lanthanides and is seldom used for the purpose of measuring electric conductance, since the complex is completely dissociated on dissolution in water. The complete dissociation of lanthanide complexes in water has been shown by molecular weight determinations in water as in the case of the complexes of DMSO (246,249, 250), PyO (147,157,158), and DMF (41, 43). Most useful data are obtained in non-aqueous solvents like nitromethane, acetonitrile, nitrobenzene, and acetone (317). 

Most samples may be prepared by dissolution in water. The final concentration should be optimized according to the aim of the analysis, counterion or impurity analysis. For the control of impurities, the main counterion may be fairly overloaded. This may have an impact on the ionic strength of the sample and will produce a disturbed peak profile for the main compound. When solubility problems are encountered, up to 30% of methanol, ethanol, or acetonitrile may be added to improve solubility. However, the presence of too much organic solvent may produce an instrumental error, because the conductivity of the sample plug will differ too much from BGE conductivity, leading to current leakage. Or, when the sample is insoluble in water, it may be suspended, vortexed, and then centrifuged. The analysis is then performed on the supernatant as the ions are water soluble. 

Chlorine is released as HCl, which dissociates upon dissolution in water to generate Cl (aq). Sulfur is released as either H2S or SO2. Both are transformed into S04(aq) through chemical reactions involving oxidation by O2 and dissociation/dissolution in water. The amounts of primary magmatic volatiles that have been degassed thus far are given in Table 21.5. About half of the chlorine has been retained in the ocean and the other half has been converted into evaporite minerals. In comparison, virtually... 

The heats of reaction/solution of some reagents as hydrolysis/dissolution takes place can cause substantial elevation in slurry/solution temperatures, particularly at a large scale where heat transfer and radiative cooUng are not nearly as efficient as it is in small laboratory vessels. Other reagents, such as certain sodium alumi-nates and particularly reagents that are not freshly prepared, may need elevated temperatures for full dissolution in water. These hot or very warm solutions can adversely affect early nucleation conditions in some zeoHte syntheses. Hot reagent solutions and mixtures are sometimes cooled prior to their addition to other reagents to better control the early reactions and speciation of aluminosilicate and silicate precursors. 

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