Parent Salt Research Articles

Non-isothermal kinetic and thermodynamic study of the decomposition of lead acetate trihydrate

The non-isothermal decomposition of lead acetate trihydrate was studied up to 450°C by means of TG, DTG, DTA and DSC measurements in a dynamic atmosphere of N2 (or dry air).The parent salt was found to undergo melting concurrently with the dehydration process, which takes place in two steps between 30 and 110°C. The anhydrous salt melts at 204°C and later forms two intermediate basic lead acetate salts, namely Pb(CH3COO)2 · PbO (between 230 and 270°C) and Pb(CH3COO)2 · 2PbO (between 275 and 325°C) respectively. The latter basic salt decomposes, between 325 and 380°C in N2 atmosphere, to produce a mixture of PbO and a small amount of metallic Pb. In air, however, the decomposition produces solid PbO only.X-ray powder diffraction and IR transmission spectroscopy were used to identify the solid intermediates and products of the reaction. Gas chromatography was used to identify the volatile products of the decomposition in N2 and in O2. Scanning electron microscopy was also used to investigate the structure changes and possible occurrence of melting during the decomposition.Values of the kinetic (ΔE and ln A) and thermodynamic (ΔH, Cp and ΔS) parameters were calculated for the dehydration and decomposition processes.

Non-isothermal decomposition of nickel acetate tetrahydrate

Non-isothermal decomposition of nickel acetate tetrahydrate was studied by means of thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) from ambient temperature up to 500°C. The parent salt was found to commence dehydration near 80°C giving the anhydrous nickel acetate, which on further heating produced basic nickel acetate. Decomposition took place above 250°C with the formation of nickel carbide (Ni 3C), which, together with the basic acetate, decomposed to a mixture of NiO and nickel metal. Kinetic parameters (Δ E and ln A) and thermodynamic parameters (Δ H and C p) are given for the dehydration and decomposition processes. Infrared spectroscopy and X-ray powder diffractometry were used to identify the solid decomposition products while gas chromatography was employed to identify the volatile decomposition products (acetic acid, acetone, CO 2, and trace amounts of CO, ethyl acetate and propionic acid). The distribution of these volatile products was found to be influenced by the prevailing atmosphere (N 2 or O 2).

A mechanistic investigation and kinetic analysis of the thermal decomposition of diammonium hexanitrato cerate catalysed by Cd xCo 1− xFe 2O 4 catalysts

The isothermal and non-isothermal decomposition of pure diammonium hexanitrato cerate(IV) and its mixtures with 10% (wt/wt) of Cd xCo 1− x Fe 2O 4 catalysts (x = 0.0, 0.5 and 1.0) were investigated. The effect of catalyst additives on the kinetics of isothermal decomposition of the parent salt was also studied. Their isothermal curves of fraction decomposed (α) against time were sigmoid in nature and the decomposition reaction in the presence of these catalyst additives obeys the Avrami-Erofe'ev equation. Such catalytic pretreatment reduced the induction period to the onset of the reaction decomposition. From the complementary consideration of microscopic observations and kinetic evidence, we conclude that the thermal decomposition of the parent salt in the presence of these catalyst additives, in the temperature range 250–325 ° C, proceeds by the nucleation-and-growth mechanism. The promotional effect of the catalysts used was also described. It can be stated that the activity of these catalysts in promoting salt breakdown is a consequence of their appreciable solubility in the parent salt and that the chemistry of the reaction in such conditions is complicated. It involves several participants, including the unstable ammine complexes of both Cd and Co ions, located in the octahedral sites of the catalysts, formed as intermediates of the type [M(NH 3)] 6 2+.

Air-stable liquid clathrates. 1. Crystal structure of [NBu4][Br3] and reactivity of the [NBu4][Br3]�5 C6H6 liquid clathrate

[NBu4][Br3] interacts with C6H6 to form an air-stable liquid clathrate. The tribromide anion reacts with phenol to give para-bromophenol in>95% yield. The HBr which is generated in the reaction combines with the Br− anion to form [Br-H-Br]−. The latter forms the basis for a new liquid clathrate, [NBu4][Br-H-Br]·n C6H6. The parent salt, [NBu4][Br3], crystallizes in the monoclinic space group C2/c witha=12.983(5),b=10.380(7),c=16.222(6) A,β=93.93(3)°, andDc=1.47 g cm−3 forZ=4. The final R value is 0.068 based on 787 observed reflections.

Messenger RNA induction in cellular salt tolerance of Alfalfa (Medicago sativa)

A salt tolerant alfalfaMedicago sativa L. cell line (HG2-N1) has been selected for growth in 171 mM NaCl. The salt tolerance characteristic is stable and is retained after growth in absence of salt selection for two months.In vitro translation was used to compare mRNA composition from the salt tolerant HG2-N1 and parent salt sensitive HG2 cell lines grown in the presence and absence of 171 mM NaCl. The results suggest that the mRNA composition differs between HG2-N1 and HG2 in a number of RNA species. The salt tolerant HG2-N1 shows both increases and decreases in specific polypeptides as compared to HG2. Many of the enhanced polypeptide bands from mRNA in the salt tolerant HG2-N1 variant appear to be constitutively expressed, since they can be detected from HG2-N1 cells grown in presence and absence of NaCl, but the expression of a few bands may depend on the presence of added NaCl. Most enhanced polypeptides, which are detected from mRNA in the salt tolerant variant HG2-N1 (grown on NaCl) are different from polypeptide bands enhanced in the salt sensitive HG2 line as a result of 24 hour salt stress. Similar results were obtained from two dimensional analysis ofin vivo labeled polypeptides. At least one isolated cDNA clone shows selective expression of mRNA in salt tolerant cells grown in NaCl. These results indicate that adaptive mechanisms for salt tolerance may differ in some aspects from acute stress mechanisms.

Auger electron spectroscopy studies of calcium containing carbon surfaces

We have shown that Auger electron spectroscopy can be used to monitor the concentration of calcium in carbon based systems and have further demonstrated that additional chemical information about the electronic environment of calcium can be obtained from the relative amplitudes of the calcium L 23 M 23 M 23 and L 23 M 23 N 1 Auger transitions. Examples of CaO by itself and with carbon powders, CaCO 3 on carbon, and a Ca 2+ ion-exchanged impregnated carbon are given. The average electronic environment of calcium following CaCO 3 decomposition on carbon is more metallic-like than the parent salt. Thermally activated Ca 2+ ion-exchanged impregnated carbon, an active gasification catalyst precursor, shows similar electronic properties.

Auger electron spectroscopy studies of calcium containing carbon surfaces

We have shown that Auger electron spectroscopy can be used to monitor the concentration of calcium in carbon based systems and have further demonstrated that additional chemical information about the electronic environment of calcium can be obtained from the relative amplitudes of the calcium L 23M 23M 23 and L 23M 23N 1 Auger transitions. Examples of CaO by itself and with carbon powders, CaCO 3 on carbon, and a Ca 2+ ion-exchanged impregnated carbon are given. The average electronic environment of calcium following CaCO 3 decomposition on carbon is more metallic-like than the parent salt. Thermally activated Ca 2+ ion-exchanged impregnated carbon, an active gasification catalyst precursor, shows similar electronic properties.

Resonance Raman of viologen radicals

The resonance Raman effect of the radical cation of4,4'-bipyridinium salts was recorded and correlated with the Raman spectra of the parent molecules. The radicals were produced either chemically or radiolytically. The correlation between the radical cation and its parent salt is then compared with the correlation between the radical anion of biphenyl and its parent molecule.

Radiation mechanisms—VIII. Radiolysis of borohydride ions in aqueous solutions. An E.S.R. study

Radiolysis of frozen aqueous or methanolic glasses containing sodium borohydride gave E.S.R. features characteristic of ·BH 3 − as the major radical product. These radicals were strongly associated with the solvent lattice in contrast with their behaviour in the parent salt. Additional E.S.R. features separated by ca. 200 G are assigned to BH 4, but since this spectrum could never be obtained in the absence of the intense BH 3 − features, this assignment is tentative.

Chemistry of oxo-metal ions-VI 1,10-phenanthrolinium oxopentachloromolybdate(V) and its derivatives

1,10 Phenanthrolinium oxopentachloro molybdate(V), PhenH 2[MoOCl 5] has been isolated as yellowish-green solid and from this salt the non-electrolytic paramagnetic complexes MoOCl 3·phen have been prepared in three different isometric (colored reddish-pink, pale brown and green) forms by dehydrohalogenation in suitable solvent and solid state reaction. Hydrolysis of the parent salt yielded the diamagnetic complex, Mo 2O 4Cl 2(phen) 2 as brownish red solid. All these products and the parent salt have been shown to be interconvertible and the probable constitution of expected cis-trans isomers of MoOCl 3·phen has also been discussed. All these compounds have been studied by various physicochemical methods and it has been shown that the oxometal entity MoO 3+ remains intact under various chemical environments.

Chemistry of oxometal-ions—V: 1, 10-phenanthrolinium oxopentabromolybdate(v) and its derivatives

1, 10-phenanthrolinium oxopentabromolybdate(v) has been isolated in pure state as greenish yellow powdery solid. During the study of its reactions, (MoOBr 3.phen) was isolated as a product of dehydrohalogenation, and (Mo 2O 3Br 4 phen 2) and (Mo 2O 4Br 2phen 2) were isolated by hydrolysing the parent salt. The compound (MoOBr 3.phen) has been isolated in two coloured forms (red and deep chocolate) expected to be the two stereoisomeric varieties cis- and trans-, as evidenced by their reactions. All the compounds have been studied using various physicochemical methods. Their interconversions clearly reveal the extraordinary stability of the various oxomolybdenum species MoO 3, Mo 2O 3 4+ and Mo 2O 4 2+ under different environments.

Complexes of some alkali-metal and silver salts with 1,4-dioxan

The 1,4-dioxan (dx) complexes NaClO4,3dx, NaBF4,3dx and NaI,3dx have the cubic structure of AgClO4,3dx. The metal ion is octahedrally co-ordinated by oxygen atoms from dioxan with Na–O distance 2·43—2·46 Å, identical to those found in Na(OH2)6 octahedral Size and shape requirements limit the anions found in complexes of this structure. The heavier alkali-metal ions are too large for the structure to be stable. The lattice energy of the parent salt is not important in selecting which alkali-metal ions form complexes with dioxan. The lattice energy of the complex is dominated by metal–dioxan ion–dipole interaction. Temperatures, enthalpies, and entopies of decomposition are reported. AgClO4,3dx decomposes to AgClO4,dx and thence to AgClO4, NaClO4,dx, and NaBF4,3dx decompose directly to the parent salt. NaI,3dx decomposes to NaI at atmospheric pressure but NaI,2dx and NaI,dx have been characterised in vacuo. Temperatures and enthalpies of phase changes in AgClO4, NaClO4, NaBF4, and NaClO4,3dx are reported.

Chemistry of oxo-metal ions—III: 2,2′-bipyridinium oxopentachloromolybdate(V) and its derivatives

Starting from molybdenum trioxide 2,2′-bipyridinium oxopentachloromolybdate(V) BipyH 2[MoOCl 5] has been isolated in pure state as greenish yellow crystalline solid. From this salt the nonelectrolytic paramagnetic complex MoOCl 3·bipy has been isolated in three different isomeric (colored reddish pink, pale khaki and green) forms by dehydrohalogenation in suitable solvent and solid state reaction. The diamagnetic complex Mo 2O 4Cl 2(bipy) 2 has been isolated by hydrolysis of the parent salt. All these products and the parent salt have been shown to be interconvertible. The constitution of expected cis-trans isomers of MoOCl 3·bipy has also been discussed. All these compounds have been studied by various physicochemical methods and it has been shown that the oxometal entity MoO 3+ remains intact under various chemical environments.

Diapirlike Structures in Southeastern Bering Sea

Six folds that we suspect have diapiric cores were located by seismic reflection profiling beneath the edges of Umnak Plateau, a broad platform at a depth near 1,860 m in the southeastern corner of the Bering Sea. The plateau is underlain by 2,000-3,000 m of generally flat-lying strata believed to be largely of Neogene age. These overlie an that probably consists of more lithified rocks of Paleogene or possibly Cretaceous age. All the diapiric (or diapirlike) folds found are along major structural trends that delineate the principal physiographic elements of the southeastern region of the Bering Sea. The piercement cores rise as much as 1,500 m above the acoustic basement and to within 700 m of the sea floor. Folding above the cores decreases upward, although the surface of the plateau is gently domed above some of them. Intrusion of the diapiric cores probably formed the folds in late Tertiary time; however, the very slight folding in the upper 200-400 m of the plateau may simply be the result of differential compaction and/or draping that followed intrusion. The cores of the folds do not produce a clearly recognizable magnetic anomaly. This may mean that the intrusive plugs are not of igneous origin, although such an origin is suggested strongly by their proximity to volcanic and intrusive rocks of late Cenozoic age on the Aleutian Ridge and at Bogoslof Island. The apparent nonmagnetic character of the diapirs and the probable presence of a thick sequence of shale beds at the base of the stratified sequence forming the plateau also strongly imply that the intrusive plugs consist of shale. The plugs could be salt diapirs; parent salt beds probably would be of early Mesozoic or Paleozoic age.

Base-Exchange and Sulphate Reduction in Salty Ground Waters Along Atlantic and Gulf Coasts

Salty waters encountered in water-bearing sands along the Atlantic and Gulf coasts do not appear to be simple mixtures of ground water with more or less sea water. When the salty waters are compared with theoretical mixtures of fresh ground waters and sea water--the ground waters being from comparable depths in the same formations and the amount of sea water being that indicated by the chloride contents of the salty waters--the natural salty waters are found to be characteristically lower in calcium, magnesium, and sulphate and higher in sodium content, suggesting that the waters have undergone base-exchange and reduction of sulphate. The indicated replacement of magnesium and calcium in the salty waters by sodium from base-exchange minerals in the sands suggests that the base-exchange minerals are not in equilibrium with present-day sea water or with salty waters formed by its admixture with fresh ground waters in which sodium bicarbonate is the predominant constituent. These relations further suggest that the water-bearing sands have at some time been flushed of salt water, at least to a point farther down the dip than at present, by water having a lower Ca/Na and Mg/Na ratio and that the salt water now contaminating the fresh waters is a new advance inland of salt water. The low sulphate content of the salty waters is attributed to reduction of sulphate, but whether the causative agent of the reduction was living organisms or inanimate organic matter or whether reduction took place at the time the sediments were deposited or subsequently can not be proved definitely at the present time. The parent salt waters of these salty waters may have been connate waters in which sulphate had been reduced--as reduction is known to take place in environmental conditions like those under which some of the sediments in the Coastal Plain were laid down. In the flushing implied by the low calcium and magnesium content of the waters the connate waters may have been forced seaward but may not have been completely flushed from the beds and subsequent lowering of the fres -water head relative to the head of sea water may have permitted the connate water to move farther inland. The fact that unselected salty waters from widely different sources, both geographically and geologically, in the Atlantic and Gulf Coastal Plain have apparently undergone similar alterations in mineral composition seems to indicate that the conditions causing these alterations are rather general throughout the area.