Structure sulphate hydrates

Different samples of aqueous solution containing radionuclides of Co and Eu were prepared at different copper sulphate concentrations and constant polymer concentrations (pAM) of 15 mg/1. The addition of salt to the system was done to reduce both the repulsion forces between the radionuclides and the interaction between the polymeric chains [7]. The polymer efficiency for the prepared samples was determined, results are shown in Fig. 15. It is clear that the polymer efficiency for Eu " is higher than for Co. This can be explained by the difference in the tightly bound structured water associated with different cationic species [14,107]. On this basis, we expect that Co is more hydrated than Eu. This is due to the difference in the ionic size. The hydra-... 

Hydrated metal sulphates have long been used to study water removal processes, and characteristic kinetic behaviour is conveniently illustrated by reference to these substances. Frost and co-workers [602,603] have investigated the structures, stabilities and adsorption properties of various intermediate amorphous phases, the immediate reaction products which can later undergo reorganization to yield crystalline phase. 

What is the structure of hydrazine, hydrazine hydrate, hydrazine sulphate, and hydroxylamine Do these compounds exhibit oxidizing properties ... 

The zeolite group of minerals provides further examples of defect structures. These are complex aluminosilicates, the crystals of which have a rigid framework of Al, Si, and O atoms in which there are continuous channels water molecules may enter or leave the crystals by way of these channels, the amount of water in the crystals being variable (W. K. Taylor, 1930, 1934). (In normal hydrates the structure collapses when water is removed, a new structure being formed.) A simple substance in which the same thing occurs is calcium sulphate subhydrate CaS04.0-fH20 (Bunn, 1941). 

The phenomenon of increased hardness occurs principally in minerals of sheet and chain structures, which link together through the cations (silicates and aluminosilicates, as well as hydrated sheet minerals, such as glauconite, melilite and gypsum—M ranging from 0 to about 1.25), and also in minerals of skeletal structures (borates, phosphates, sulphates, nitrates, carbonates, such as calcite, dolomite and others—Ah from 0 to about 1.15). For this reason, the hardness analysis of minerals with weak bonds demands consideration of the fact that just as the basic crystallo-chemical factors, so is hardness influenced by the form of domains (component parts of structures) in all anisodesmic minerals of chain, sheet or skeletal structure. Depending on the form of domain (and also according... 

Flydrolysis is an important metabolic reaction for drugs whose structures contain ester and amide groups. All types of ester and amide can be metabolized by this route. Ester hydrolysis is often catalysed by specific esterases in the liver, kidney and other tissues as well as non-specific esterases such as acetylcholinesterases and pseudocholinesterases in the plasma. Amide hydrolysis is also catalysed by non-specific esterases in the plasma as well as amidases in the liver. More specific enzyme systems are able to hydrolyse sulphate and glucur-onate conjugates as well as hydrate epoxides, glycosides and other moieties. 

Very recent studies have examined the possibility of using 33S MAS spectroscopy in the study of some structural problems in cementitious materials107 108 and in sulphur speciation in silicate melts.109 Several processes of the deterioration of cements and more generally lapideous materials can be correlated to the stability of sulphate, to changes in the sulphate phase and to the interaction of sulphate ions with water molecules and hydrates.108 Since sulphate anion is one of the species that can be studied more easily by 33S NMR solid-state spectroscopy, this technique can be a valuable tool in studying... 

Froment and co-workers " have employed REFLEXAFS (vide supra) for studying passive films on iron and nickel. Their early studies were concerned with demonstrating the applicability of the REFLEXAFS technique to electrochemical systems. Most recently, they have used this technique to study the structure of passive films on Ni and on Ni-Mo alloy electrodes. For the Ni electrodes, they performed studies after reduction at — 700 mV (vs. saturated mercurous sulphate electrode) as well as in the passive (-l-3(X)mV) and transpassive (-1-800 mV) regions. The Fourier transforms for the films in the passive region have a Ni—O peak at a distance that corresponds closely to that in bulk nickel oxide. However, no Ni-Ni interactions were observed. These investigators interpreted these results as consistent with a model that postulates an amorphous hydrated polymeric oxide. ... 

The characteristic features of hydrate structures of this type may be best illustrated by describing in detail one typical such compound and by then considering only briefly a number of others which have been studied. The structure which we select for discussion is that of beryllium sulphate tetrahydrate. 

A second difference between ammines and hydrates, again arising from the small dipole moment of the ammonia molecule, is that strong bonds cannot be formed between these molecules they are therefore found in ammines only in a co-ordinating and never in a structural capacity. For this reason the ammine counterparts of hydrates with an odd number of water molecules do not exist, and it is interesting to note, as an example of this point, that cupric sulphate forms only the hydrated ammine Cu(NH3)4S04. H20 and not the compound Cu(NH3)4S04. NH3. 

Lehmann drew attention to some features in solid-state reactions, including the curious observations described in 1834 by Faraday, which are now considered as pioneering experimental studies of the structural sensitivity of the dehydration rate of crystalline hydrates. Crystals of easily eroding sodium salts (carbonates, phosphates, and sulphates), stored by Faraday for a few years, did not exhibit any visible deterioration. A fresh scratch on the crystal surface (birth of mechanochemistry) initiated, however, the onset of intense dehydration with a gradual expansion of the erosion zone until it covered the crystal s entire surface. 

Proton chemical shifts in aqueous solutions of Al i nitrate, perchlorate, and sulphate have been measured over a range of temperatures, and the effects of hydrolysis and addition of acid have been studied in detail. These arise from changes in the interactions between the bulk water and three different environments, viz. [Al(OH2)e] + itself, the second hydration sphere of this cation, and the broken-water structure around the anion. ... 

Certain compounds contain crystalline water as part of their structure and form hydrates. This water can be driven off by heating. One of the hydrates of sodium sulphate (Na2S04), for example, is its decahydrate, Na2S04 lOHOH. 

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