Sol Sulfur

Smith DK, Diederich F (2000) Supramolecular Dendrimer Chemistry - A Journey Through the Branched Architecture. 210 183-227 Stec WJ, see Guga P (2002) 220 169-200 Steudel R (2003) Aqueous Sulfur Sols. 230 153-166 Steudel R (2003) Liquid Sulfur. 230 80-116... 

Chiu G, Meehan EJ. 1977. Monodisperse sulfur sols from the air oxidation of hydrogen sulfide solutions. Journal of Colloid and Interface Science 62 1-7. 

In the remainder of this section we see how the theoretical calculations of Mie account for the observed spectrum of colloidal gold. In the next section we consider the inverse problem for a simpler system how to interpret the experimental spectrum of sulfur sols in terms of the size and concentration of the particles. Both of these example systems consist of relatively monodisperse particles. Polydispersity complicates the spectrum of a colloid since the same x value will occur at different X values for spheres of different radii according to Equations (99M101). 

Another colloidal system with light scattering characteristics that have been widely studied is the so-called monodisperse sulfur sol. Although not actually monodisperse, the particle size distribution in this preparation is narrow enough to make it an ideal system for the study of optical phenomena. 

Formulate a generalization correlating the observed number of green bands in the HOTS for this system with the approximate particle size. Briefly describe how this information could be used to grow a monodisperse sulfur sol with a dimension that corresponds aproximately to a predetermined size. 

Make a colloidal sol of iron(m) hydroxide by adding aqueous iron(m) chloride to boiling water, or a colloidal sulfur sol by adding dilute aqueous sodium thiosulfate to hydrochloric acid. For both of these sols, it can be shown that the solid phase is not separated by filtration. 

Determination of the time dependence of particle size distribution and number concentration in a growing system has been evaluated on the well-known LaMer sulfur sols (18, 19, 9), an extensively studied system (5). 

See the review on aqueous sulfur sols hy R. Steudel, Top. Curr. Chem. 2003, in print. 

Abstract Sulfur sols are colloidal solutions of elemental sulfur or of sulfur-rich compounds. The particles in these solutions have diameters of O.l-l.O iim and consist either of Ss molecules (hydrophobic sulfur sols) or of chain-like sulfur compounds with hydrophilic end groups like sulfonate or functionalized organic groups (hydrophilic sulfur sols). Both types of sols are stabilized by the negative charge of the particles which results in mutual repulsion. Therefore, cations and especially multivalent cations are able to precipitate the sol particles. While hydrophilic sulfur sols can be prepared with sulfur concentrations of up to 600 g hydrophobic sols are much more dilute (<0.1 g 1 ). Sols of these types occur both in industrial desulfurization plants where sulfide is oxidized to elemental sulfur as well as in cultures of certain oxidizing sulfur bacteria. 

Emulsions of very small droplets of liquid sulfur or of sulfur-rich compounds (e.g., polythionates) in water are called sulfur sols . Such mixtures can be prepared by a variety of methods. Hydrophobic sulfur sols are obtained on dilution of saturated solutions of elemental sulfur in organic solvents like ethanol or acetone with a large excess of water. These preparations are usually called Weimarn sols honoring the principal author who first re-... 

Weimarn sols are metastable but exist only at rather low sulfur concentrations (<0.1 g 1 ) while stable Raffo sols with up to 600 g have been prepared. Thermodynamically, all sulfur sols are unstable with respect to transformation into orthorhombic sulfur Ss which is water-insoluble and precipitates from the solution. 

Sulfur sols play an important role in certain industrial desulfurization processes where elemental sulfur is formed [5]. This sulfur sometimes stays in the liquid state for several days creating separation and clogging problems. Furthermore, certain sulfur bacteria produce so-called globules of liquid sulfur or sulfur-rich compounds by oxidation of sulfide HS, thiosulfate 8203 or polythionate ions S 03 (see later). The characterization of these globules has considerably stimulated the interest in sulfur sols in recent years. 

Historically, aqueous sulfur sols are related to the so-called Wacken-roder s solution which is obtained by reaction of H2S with SO2 in water at 0 °C and which contains polythionic acids as well as elemental sulfur besides other sulfur compounds (e.g., sulfate). For a detailed early investigation and vivid description of this mixture, see ref. [6] for more recent studies, see later. A compilation of 23 patents for the preparation of colloidal sulfur mixtures from the years 1931-1948 has been published by Meyer [7]. 

Hydrophobic sulfur sols can also be prepared by blowing sulfur vapor into cold water where it immediately condenses [17]. After filtration these sols are polydisperse, exhibit a strong Tyndall phenomenon, and can be kept for two to six weeks at 20 °C before the sulfur starts to settle to the bottom of the flask. The crystalline precipitate obtained in this way cannot be peptized in water but dissolves quantitatively in carbon disulfide. The sulfur content of the original but filtrated sol was between 0.01 and 0.08 mass % the particles are negatively charged and move in an electrical field to the anode. 

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