Salt-hydrate melt

Jin et al. [10] used a so-called salt-hydrate melt as a dissolving agent, being a mixture of water and Ca(SCN)2 at a composition close to the coordination number of the salt cation... 

Figure 9.3. Strength of cellulose aerogels as prepared by Jin and co-workers [10] using a salt-hydrate melt to dissolve cellulose (calcium thiocyanate/water) and regeneration of the cellulose in alcohols (redrawn from [10] different units used here).

A linear variation of the aerogel density of cellulose concentration should be observed on simple theoretical grounds. If Pa denotes the density of the aerogel and Wc is the salt hydrate melt weight fraction having a density then for small concentration, Wc << 1, the aerogel density should obey the relation. 

Salt-Hydrate melt A concentrated solution of salts in water at higher temperature leading... 

Also shown in Table 5.5 are the molar electrostriction volumes, Aji F, of the hydrated salt melts, which are negative quantities. These are the differences between the molar volume of the salt hydrate melts V (at. T and the sum of the intrinsic volume of the ions, weighted by their stoichiometric coefficients in CpA nH20, plus n times the molar volume of water VV ... 

Ruthenium (IV) oxide [12036-10-1] M 133.1, d 6.97. Freed from nitrates by boiling in distilled water and filtering. A more complete purification is based on fusion in a KOH-KNO3 mix to form the soluble ruthenate and perruthenate salts. The melt is dissolved in water, and filtered, then acetone is added to reduce the ruthenates to the insoluble hydrate oxide which, after making a slurry with paper pulp, is filtered and ignited in air to form the anhydrous oxide [Campbell, Ortner and Anderson Anal Chem 33 58 1961]. 

The effect of phase separation, also called semicongruent or incongruent melting, is a potential problem with PCM consisting of several components. Phase separation is explained in Figure 104 with a salt hydrate as example. 

The precise determination of the composition of individual fluid inclusions in the H20-NaCI-(Ca,Mg)Cl2 system from low temperature microthermometry is often limited by the difficulties in observing the melting of salt hydrates and by their common metastable behaviour. To add, the liquid phase can fail to nucleate any ice or hydrate during cooling down to -190°C. 

Salt Hydration Form Melting point (°C) Aqueous solubility (mg/mL) Weight change (%) Relative humidity (%) ... 

Some salts that melt at low temperatures can disperse spontaneously onto the surface of a suitable support even at room temperature. Worthy of special mention is the behavior of HgCI2 mixed with active carbon. This low-melting-point salt disperses at 30°C onto a support having a very specific surface, namely, active carbon, at a noticeable rate, as is shown in Fig. 9. Hydrated nitrates and chlorides can also disperse spontaneously at ambient or mild temperatures onto the surface of y-Al203, as is evidenced in Fig. 10. 

Tucholski determined the dehydration temperatures of picric acid salts hydrates, their melting points, initiation temperatures and temperatures preceding explosion. T. Urbanski and Sion determined their sensitiveness to impact and flame. 

When alkylammonium salts are recrystallized from water, they often form solids with very low melting points (Fowler et al., 1940). An example is (iso-Am)4N+.F- 40 H20 whose structure (Feil and Jeffrey, 1961) shows that the amyl groups are held in cages of water molecules located tetrahedrally around the N+-charge centre of the onium ion (Fig. 11). Similar structures are observed in tetra-n-butylammonium (McMullan et al., 1963 Bonamico et al., 1962) and tri-n-butylsulphonium salt hydrates (Beurskens and Jeffrey, 1964). 

When salt hydrates are melted under C02 pressure, the gas is reversibly absorbed. Thus (Me4N)F-4H20 at 50°C and 100 kPa absorbs C02 to give a concentration ca 1.9 M. This may lead to new methods for removal of C02 from gas streams.29... 

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