Equilibrium Polymerization of Sulfur

Tobolsky, A. V.; Eisenberg, Adi

doi:10.1021/ja01513a004

Cited by 275 publications

(126 citation statements)

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“…Although the temperature is not necessarily the same between the two vents, this agreement is more than satisfactory considering that this slick contains much (>70%) CS2-insoluble, polymer ized sulfur (Table 2). A high amount of polymer ized sulfur is one of the chemical characteristics of molten sulfur at high temperatures over 159°C (Tobolsky and Eisenberg, 1959). When we apply this method for estimating a subaqueous vent temperature, sulfur slicks should be as fresh as possible.…”

Section: Dissolved Gases In Molten Sulfurmentioning

confidence: 99%

Geochemical implications of subaqueous molten sulfur at Yugama crater lake, Kusatsu-Shirane volcano, Japan.

1994

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Crater lakes with active subaqueous fumaroles often contain molten sulfur pools on the lake floor. Volcanic gases passing through the sulfur pools carry hollow spherules of solidified molten sulfur to the surface of crater lakes. This sulfur dissolves SO2 and H2S gases and releases these gases into the water. The sulfur also contains homocyclic sulfur (cycl. S, x = 6-16) and probably sulfane monosulfonates. The concentration of cyclic S7 increases with increasing temperature between 120 and 175°C, which is useful to estimate the temperatures of subaqueous molten sulfur pools. The gases drastically lower viscosity of the molten sulfur. This may be due to blockage of growing long-chain sulfur molecules by the dissolved gases. Thus a jump in viscosity at 159°C observed for pure sulfur is not likely to be present in subaqueous molten sulfur at crater lakes. Based on the chemistry and morphology of sulfur slicks, activity of subaqueous fumaroles can be divided into four stages (I-IV), each of which may serve for qualitative in situ monitoring of crater lakes. At Stage I, no molten sulfur pools exist on the lake floor and fumaroles discharge low temperature gases (<119°C) containing only traces of SO2; at Stage II, subaqueous molten sulfur pools (119°C < T < 150°C) are formed, releasing yellow hollow spherules of sulfur with no tails; at Stage III, the fumarolic temperature increases to >150°C, resulting in an increase in molten sulfur viscosity; and at Stage IV, frequent phreatic or geyser-like eruptions are observed. The molten sulfur pools are dispersed into pieces on the lake floor at this stage.

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Section: Dissolved Gases In Molten Sulfurmentioning

confidence: 99%

Geochemical implications of subaqueous molten sulfur at Yugama crater lake, Kusatsu-Shirane volcano, Japan.

1994

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“…Although this phenomenon, known as λ-transition (T λ = 159 o C), has been tackled for more than 150 years, its comprehension is still far from being reached: to rationalize this puzzling temperature dependence of viscosity, indeed, a liquid-liquid transition from a monomeric (i.e. a S8 rings liquid) to a polymeric phase has been invoked [7,8]. The temperature dependence of the mass fraction of S atoms participating in the polymeric component turns out to be a central parameter for extracting information on many thermodynamic aspects of the λ-transition [9,10].…”

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confidence: 99%

Origin of theλTransition in Liquid Sulfur

et al. 2007

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Developing a novel experimental technique, we applied photon correlation spectroscopy using infrared radiation in liquid Sulphur around T λ , i.e. in the temperature range where an abrupt increase in viscosity by four orders of magnitude is observed upon heating within few degrees. This allowed us -overcoming photo-induced and absorption effects at visible wavelengths -to reveal a chain relaxation process with characteristic time in the ms range. These results do rehabilitate the validity of the Maxwell relation in Sulphur from an apparent failure, allowing rationalizing the mechanical and thermodynamic behavior of this system within a viscoelastic scenario. PACS numbers: 62.60.+v,64.70.Ja,62.10.+s, Common wisdom holds that liquids become less viscous as the temperature is raised. On a microscopic ground, indeed, viscosity can be regarded as arising from continual brushing of molecules which are close to each other. On increasing temperatures the more vigorous thermal motion of the molecules is expected to render such mutual friction progressively less effective. This naive description provides a qualitative interpretation of the decrease in viscosity normally observed in almost all substances as the temperature increases. There exist, however, a few remarkable exceptions exhibiting complex behavior, which can be regarded as extreme examples of how critically viscosity depends upon molecular interactions. Specifically, there are ranges of temperatures in which the viscosity of Sulphur exhibits anomalous temperature dependence. In the liquid state, just above melting (T m =119 o C), eight-membered rings (S8) are the most abundant species, and the viscosity slightly decreases with temperature as normally expected, reaching values as low as 0.01 Pa·s at T = 157 o C. Further increase of temperature causes a dramatic increase of viscosity [1], accompanied by gross changes in optical [2,3,4] and thermodynamic [5,6] properties, which, at T ≈185 o C, reaches a maximum value of 100 Pa·s. Beyond this temperature, a gradual viscosity decrease is observed. Although this phenomenon, known as λ-transition (T λ = 159 o C), has been tackled for more than 150 years, its comprehension is still far from being reached: to rationalize this puzzling temperature dependence of viscosity, indeed, a liquid-liquid transition from a monomeric (i.e. a S8 rings liquid) to a polymeric phase has been invoked [7,8]. The temperature dependence of the mass fraction of S atoms participating in the polymeric component turns out to be a central parameter for extracting information on many thermodynamic aspects of the λ-transition [9,10]. This phenomenon has been classified as a living polymerization [11] transition that essentially involves two steps, the initiation (formation of diradicals through opening of S8 rings) and propagation (concatenation of species to form long polymeric chains). Thermo-chemical models were developed in the past [12,13,14] to relate the transport properties of liquid sulphur to the underlying polymerization phenomenon. T...

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“…The difference between T max ͗L͘ and the estimated polymerization temperature (T max ͗L͘ ϪT f ϳ50 K, using the T f ϭ450 K estimate given below͒ is somewhat higher than the range (ϳ10 K) predicted by previous theoretical studies 21 and by experimental data. 12 The difference is probably due to the rounding of the transition in our simulations, since lower values of ⌬E b enhance the concentration of unsaturated atoms.…”

Section: B Resultsmentioning

confidence: 56%

“…The enthalpies of the initiation and propagation (⌬H P ) step have been estimated by Tobolsky and Eisenberg 21 to be 32.8 and 3.17 kcal/mol, respectively. A more recent estimate of the propagation enthalpy yields ⌬H P ϭ4.5 kcal/mol.…”

Section: ͑2͒mentioning

confidence: 99%

“…Polymerization is enhanced greatly by the presence of even small amounts of S 6 and S 7 molecules. 17,18 Thermodynamic properties of sulfur close to the transition have been surveyed, 19 and early theoretical studies based on thermodynamics, kinetic equations, and mean field schemes [20][21][22][23] achieved a reasonable description of the transition. Renormalization group approaches, accounting for fluctuations and non-mean-field features, have been applied by Wheeler and co-workers.…”

Section: Introductionmentioning

confidence: 99%

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Density functional and Monte Carlo studies of sulfur. II. Equilibrium polymerization of the liquid phase

Ballone

Jones

2003

The Journal of Chemical Physics

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The equilibrium polymerization of sulfur is investigated by Monte Carlo simulations. The potential energy model is based on density functional results for the cohesive energy, structural, and vibrational properties as well as reactivity of sulfur rings and chains ͓Part I, J. Chem. Phys. 118, 9257 ͑2003͔͒. Liquid samples of 2048 atoms are simulated at temperatures 450рTр850 K and Pϭ0 starting from monodisperse S 8 molecular compositions. Thermally activated bond breaking processes lead to an equilibrium population of unsaturated atoms that can change the local pattern of covalent bonds and allow the system to approach equilibrium. The concentration of unsaturated atoms and the kinetics of bond interchanges is determined by the energy ⌬E b required to break a covalent bond. Equilibrium with respect to the bond distribution is achieved for 15р⌬E b р21 kcal/mol over a wide temperature range (Tу450 K), within which polymerization occurs readily, with entropy from the bond distribution overcompensating the increase in enthalpy. There is a maximum in the polymerized fraction at temperature T max that depends on ⌬E b . This fraction decreases at higher temperature because broken bonds and short chains proliferate and, for T рT max , because entropy is less important than enthalpy. The molecular size distribution is described well by a Zimm-Schulz function, plus an isolated peak for S 8 . Large molecules are almost exclusively open chains. Rings tend to have fewer than 24 atoms, and only S 8 is present in significant concentrations at all T. The T dependence of the density and the dependence of polymerization fraction and degree on ⌬E b give estimates of the polymerization temperature T f ϭ450Ϯ20 K.

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Equilibrium Polymerization of Sulfur

Cited by 275 publications

References 0 publications

Geochemical implications of subaqueous molten sulfur at Yugama crater lake, Kusatsu-Shirane volcano, Japan.

Geochemical implications of subaqueous molten sulfur at Yugama crater lake, Kusatsu-Shirane volcano, Japan.

Origin of theλTransition in Liquid Sulfur

Density functional and Monte Carlo studies of sulfur. II. Equilibrium polymerization of the liquid phase

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