Salt dehydration

Piperazine phosphate (H2O) [18534-18-4] M 197.6. Crystd twice from water, air-dried and stored for several days over Drierite. The salt dehydrates slowly if heated at 70 . 

Ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA) buffer solution... 

The chiral chloride salt is stable for years when kept dry and in the dark, preferentially in a refrigerator at — 15 °C. When heated, the solid salt dehydrates and undergoes racemization.11 In acid solution the A-cis-[Cr(en)2Cl2] + cation aquates to A-cis-[Cr(en)2(H20)Cl]2+ followed by racemization of this complex. In acid solution, Ag+-assisted hydrolysis leads to the A-cis-[Cr(en)2(H20)2]1+ complex.12... 

Lamberth, C. Burgess reagent ([methoxycarbonylsulfamoyl]triethylammonium hydroxide, inner salt) dehydrations and more. J. Prakt. Chem./Chem.-Ztg. 2000, 342, 518-522. 

Though salt dehydration was not accompanied [27] by particle disintegration, the anhydrous pseudomorph was shown by X-ray diffiaction measurements to be very poorly crystallized (a characteristic feature of many nickel carboxylates). Decomposition in air (554 to 631 K) proceeded at a constant rate (0.1 < nr < 0.8 and = 96 kJ mol" ), ascribed to the operation of an autocatalytic mechanism. The reaction in vacuum (562 to 610 K) gave a sigmoid ar-time curve which was fitted by the Prout-Tompkins equation. Because the activation energy was the same as that for reaction in air, it was concluded that the same mechanism operated. The reaction in air yielded residual nickel oxide, while reaction in vacuum gave the carbide with excess carbon and some oxide. In addition to carbon dioxide, the volatile products of decomposition included water and acetic acid. 

The decomposition kinetics of nickel squarate [112] were difficult to measure reliably due to the sensitivity to salt dispersion within the reaction vessel This behaviour was a consequence of the overlap and interaction of the reversible salt dehydration and irreversible decomposition steps in the same temperature interval ... 

Derivation (1) Action of air, steam, or carbon dioxide on iron (2) specially pure grade by precipitating hydrated ferric oxide from a solution of iron salts, dehydrating, and reducing with hydrogen, (3) occurs in nature as the mineral magnetite. 

Formula weight (NagHsPgOg 6 HgO) 314.04. Forms tabular, monoclinic crystals. Stable in air at room temperature loses its water of c stallization upon gentle heating. The salt, dehydrated at 100, melts at 250°C and decomposes at r heat, evolving flammable phosphine, d (20°C) 1.8. 

Salt dehydration. Direct esterification requires high purity materials in equimolar amounts because esterifications rarely go beyond 98% completion in practice. To overcome this, hexamethylene diamine and a dibasic acid such as adipic acid can be reacted to produce a nylon salt, hexamethylene diammonium adipate. A solution of 0.5-mol diamine in a mixture of 95% ethanol (160 cm ) and distilled water (60 cm ) is added to 0.5-mol diacid dissolved in 600 cm of 95% ethanol over a period of 15 min. The mixture is stirred for 30 min during which time the nylon salt precipitates as a white crystalline solid. This can be recrystallized and should melt at 456 K. The pure salt can be converted into a polyamide by heating it under vacuum in a sealed tube, protected by wire gauze, at about 540 K in the presence of a small quantity of the diacid, e.g., 10 g salt to 0.55-g adipic acid is a suitable mixture. If a lower molar mass is desired, a monofunctional acid can replace the adipic acid and act as a chain terminator. 

Because of the low reactivity of the carboxylate ion toward nucleophilic addition-elimination, further reaction does not usually take place in aqueous solution. However, if we evaporate the water and subsequendy heat the dry salt, dehydration produces an amide ... 

I.OA/HCIO4. Previous studies indicated that the presence of perchlorate salts dehydrate the metallopolymer and make the morphology of the layer considerably more compact. Hence we may expect inhibited penetration of Fe " (aq) into the polymer matrix. Thus a decrease in permeation would decrease the reaction layer thickness and lead to a changeover in the kinetic zone from Lk to a surface type. Koutecky-Levich plots for this system are illustrated in Fig. 2.20. These are all linear, and they have the same slope as that observed for a bare electrode. However examining the dependence of k E on layer thickness L (see Fig. 2.21), we note that the reaction order is zero with respect to L. From the diagnostic scheme in Table 2.2 we see that the two possibilities are Sk or LSk. Both of these are surface cases. To distinguish between these two possibilities, we must as before examine the dependence of k E on mediator concentration ho- From Table 2.2 we see that for the Sk case a reaction order of 1/2 is expected, whereas for the LSk situation, the reaction order is unity. A typical Nemst-type plot obtained via potential step coulometry is illustrated in Fig. 2.22. In this case the plot deviates significantly from linearity then there are very reduced or very oxidized layers hence the thermodynamics of the Os(III/II) transformation in perchlorate media is rather complex. This... 

We note that for nonionic surfactants, the addition of salt is about 100 times less efficient compared with ionic surfactants. In the latter case, there is a remarkable effect even if the salt concentration is on the order of 10 mM, while for nonionic surfactants there is an effect for salt concentrations even on the order of 1 M. In the latter case, the mechanism is that salt dehydrates the EO chain, while in the former case the mechanism is that the salt increases the counterion binding and hence decreases the ionic repulsion between the surfactant head groups. Thus, by knowing the mechanisms, we conclude that, for the ionic systems, adding a divalent counterion would be much more efficient compared with a monovalent counterion. For the nonionic surfactant systems, the anion is the deciding partner, while changing the cation hardly affects the CPP of the system. Here di- and trivalent anions are much more efficient compared with monovalent anions. 

If the yeast extract is produced by plasmolysis, cellular degradation is initiated by high salt levels. The salt dehydrates the cell, eventually resulting in death and liberation of cellular enzymes. While Nagodawithana [11] noted that there are several advantages to this approach, he stated that the product is typically higher in salt than desired. This limits its use in the food industry. 

Zinc chloride sodium chloride Reactions in fused salts Dehydration of alcohols... 

A major advantage of melt polymerization by salt dehydration is that the use of a pure salt guarantees exact 1 1 stoichiometry. 

Salt dehydration is a convenient reaction which can be used to produce the polyamide nylon 6.6 which is used widely as a textile fibre. The monomers used are hexamethylene diamine and adipic acid, but a normal condensation reaction is not employed. Instead the stoichiometric balance is ensured by utilizing the tendency for the two monomer molecules to form a 1 1 salt which can be crystallized from solution helping to purify the... 

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