Presence Of Thiosulphate Research Articles

Corrosion of Carbon Steel by Shewanella chilikensis DC57 Under Thiosulphate and Nitrate Reducing Conditions.

Shewanella chilikensis DC57 is a bacterial strain isolated from a corrosion failure in a floating oil production system. Previous studies have indicated that this microorganism has potential to trigger corrosion of carbon steel through several metabolic pathways identified in its genome. In this study we evaluated the corrosion of carbon steel by S. chilikensis in the presence of thiosulphate or nitrate as terminal electron acceptors of the anaerobic respiration. Electrochemical response of carbon steel to the biofilm formation revealed differences in the corrosion process under the different electron acceptors conditions. Microscopic examination of the metal surface confirmed that S. chilikensis induced corrosion in both scenarios; however, in the presence of thiosulfate S. chilikensis triggered a higher pitting corrosion rate, whereas in presence of nitrate it promoted higher uniform corrosion. This study demonstrates the importance of understanding the metabolic versatility of microbes in order to assess the MIC risk of industrial facilities.

Characterisation of bacterial communities from an active mining site and assessment of its potential metal solubilising activity

The present work is the first report characterising bacterial communities recovered from sulphide ore from a Portuguese active mine (Neves-Corvo) and collecting samples from three independent processing stages (feed/tailings/paste), at three sampling periods over 15 months. The recovered bacterial communities demonstrated low richness and heterogeneity (intra/inter-samples). Neutrophile sulphur-oxidising chemolithoautotrophs (e.g., Thiobacillus, Halothiobacillus, Thiomicrospira) were the most abundant organisms found across all samples. The presence of these primary producers may explain the occurrence of mixotrophs and facultative chemolithoheterotrophs/chemoorganoheterotrophs (e.g., Limnobacter, Paracoccus, Marinobacter, Alishewanella, Pseudomonas) in these non-acidic (4.6 < pH> 8.7), pyrite-rich environments.The capacity of the surviving bacterial community following ore processing (tailings) to solubilise metals from mine wastes was also assessed. After 65 days at room temperature and in the presence of thiosulphate as an additional energy source, the tailings’ bacterial community solubilised pollutants detected in acid mine drainage waters, namely As (96%), Cd (58%), Cu (24%) and Zn (56%) with the concomitant decrease of pH from 7.4 to 1.8. The low solubilisation efficiencies obtained for copper, zinc, and cadmium indicate a limited technological potential of these communities. However, their ability to significantly mobilise noxious pollutants from the mine wastes to the liquid medium, particularly for As, raises environmental concern. This finding should increase awareness among stakeholders for the need to increase studies at field scale, in real scenarios.

Spectrophotometric Determination of Sulphite in Various Water Samples Via Chromium-1,5-Diphenylcarbazide Complex

A simple and rapid spectrophotometric method for the determination of sulphite SO3-2 is described. The method is based on the rapid reduction of known amount of chromate CrO4-2 in the presence of sulphite in acidic medium of 2N H2SO4. The amount of excess of chromate was measured after it reactions with 1,5-diphenylcarbazide which finally gives a pink-violet, water soluble and stable complex, which exhibit a maximum absorption at 542 nm. Beer's law was obeyed in the concentration range from 0.004-6.0 µg of sulphite in a final volume of 25 ml with a molar absorbtivity of 4.64×104 l.mol-1.cm-1, Sandal's sensitivity index of 0.001724 ?g .cm-2 and relative standard deviation of ±0.55 - ±0.83 depending on the concentration level. The present method has been developed for the determination of sulphite in the presence of thiosulphate. Good recoveries of sulphite from various water samples are achieved using the proposed method.

Spectrophotometric Determination of Sulphite in Various Water Samples Via Chromium-1,5-Diphenylcarbazide Complex

A simple and rapid spectrophotometric method for the determination of sulphite SO3-2 is described. The method is based on the rapid reduction of known amount of chromate CrO4-2 in the presence of sulphite in acidic medium of 2N H2SO4. The amount of excess of chromate was measured after it reactions with 1,5-diphenylcarbazide which finally gives a pink-violet, water soluble and stable complex, which exhibit a maximum absorption at 542 nm. Beer's law was obeyed in the concentration range from 0.004-6.0 µg of sulphite in a final volume of 25 ml with a molar absorbtivity of 4.64×104 l.mol-1.cm-1, Sandal's sensitivity index of 0.001724 ?g .cm-2 and relative standard deviation of ±0.55 - ±0.83 depending on the concentration level. The present method has been developed for the determination of sulphite in the presence of thiosulphate. Good recoveries of sulphite from various water samples are achieved using the proposed method.

High rates of anaerobic oxidation of methane, ethane and propane coupled to thiosulphate reduction.

Anaerobic methane oxidation coupled to sulphate reduction and the use of ethane and propane as electron donors by sulphate-reducing bacteria represent new opportunities for the treatment of streams contaminated with sulphur oxyanions. However, growth of microbial sulphate-reducing populations with methane, propane or butane is extremely slow, which hampers research and development of bioprocesses based on these conversions. Thermodynamic calculations indicate that the growth rate with possible alternative terminal electron acceptors such as thiosulphate and elemental sulphur may be higher, which would facilitate future research. Here, we investigate the use of these electron acceptors for oxidation of methane, ethane and propane, with marine sediment as inoculum. Mixed marine sediments originating from Aarhus Bay (Denmark) and Eckernförde Bay (Germany) were cultivated anaerobically at a pH between 7.2 and 7.8 and a temperature of 15 °C in the presence of methane, ethane and propane and various sulphur electron acceptors. The sulphide production rates in the conditions with methane, ethane and propane with sulphate were respectively 2.3, 2.2 and 1.8 μmol S L(-1) day(-1). For sulphur, no reduction was demonstrated. For thiosulphate, the sulphide production rates were up to 50 times higher compared to those of sulphate, with 86.2, 90.7 and 108.1 μmol S L(-1) day(-1) for methane, ethane and propane respectively. This sulphide production was partly due to disproportionation, 50 % for ethane but only 7 and 14 % for methane and propane respectively. The oxidation of the alkanes in the presence of thiosulphate was confirmed by carbon dioxide production. This is, to our knowledge, the first report of thiosulphate use as electron acceptor with ethane and propane as electron donors. Additionally, these results indicate that thiosulphate is a promising electron acceptor to increase start-up rates for sulphate-reducing bioprocesses coupled to short-chain alkane oxidation.

Stress corrosion cracking of LDX 2101® duplex stainless steel in chloride solutions in the presence of thiosulphate

SCC behaviour of a LDX 2101® stainless steel was studied through SSRT in a 20% NaCl solution at 80°C and in the standard NACE TM-0177 solution at 25°C in the presence of S2O32-. Some tests were also performed in the NACE solution at various pH or temperatures. The LDX 2101® was susceptible to SCC in the presence of small thiosulphate concentrations. The selective corrosion of the ferrite phase became the main cause of failure when the thiosulphate concentration was increased to 0.1M in the 20% NaCl at 80°C or when NACE solution temperature was raised to 80°C.

Sulphur speciation in lazurite-type minerals (Na,Ca)8[Al6Si6O24](SO4,S)2 and their annealing products: a comparative XPS and XAS study

Sulphur speciation in lazurites and products of their high-temperature annealing in air or under various buffers is studied using S 2p X-ray photoelectron spectroscopy (XPS) and S K -edge XANES spectroscopy. The XPS as a more surface sensitive technique gives for instance less information on sulphide in the samples with oxidized surfaces whereas XANES spectroscopy enables access to such species in the bulk structure. However, both methods clearly indicate sulphate and polysulphides as main constituents in the structural cages of lazurites. Additionally, the data show sulphur species, such as sulphite, which mainly occur in a near-surface form, thiosulphate, monosulphide, and elemental sulphur. The non-cubic (orthorhombic and triclinic) lazurites – rich in sulphide – are characterized by high contents of polysulphide anions, which make up more than 20 at% of the total S. The cubic variety with low to medium S/SO 4 ratios contains less polysulphide species. The lower limit of polysulphide (primarily S 3 − ) responsible for the blue colour of lazurite is ~0.4 at%. However, in some cases there is no explicit correlation between blue colour and polysulphide content. Two types of transformation of polysulphide are considered. With high access of O 2 (fine grained powders) polysulphide may interact with sulphate anions to form sulphite ions, and in presence of thiosulphate, sulphate and elemental sulphur result. It appears to be the most probable mechanism for non-cubic lazurites rich in polysulphide. In the absence of access to air oxygen (in coarse grains), S 3 − can be transformed by the interaction with sulphate to thiosulphate and possibly to S 2 O − , or by disproportionation into S° and S 2− . The formation of S° is rarely observable in natural lazurites. Additional anions can participate in the reactions of more abundant sulphate and polysulphide anions giving rise to the formation and degradation of colour centres. Structural modifications of lazurite show different anionic compositions in their cages and, hence cannot be considered polymorphs in the strict sense. They rather represent phases of variable compositions depending on temperature, SO 2 fugacity, ordering and ratios of clusters containing Na and Ca. Modulations of the lazurite structure are possibly controlled by three types of clusters that are polysulphide, thiosulphate, and sulphate (nosean-type and hauyne-type), whose compositions and ratios depend on external (temperature, redox conditions) and internal factors (sulphur content, Na/Ca ratio).

Removal of Methylene Blue from aqueous solution by adsorption on sand

The removal of Methylene Blue (MB) dye from aqueous solution present as a pollutant material in textile waste water was studied at 298 K in terms of its adsorption behaviour. Local sand sample was used as an adsorbent in this work. The textural properties of the sand including surface area, mean pore radius and total pore volume were examined from the low-temperature adsorption of nitrogen at 77 K. The conditions for maximum adsorption of the dye on sand were optimized. It was seen that under optimized conditions, up to 92% dye could be removed from solution onto the sand surface. The adsorption data were fitted to Freundlich and Dubinin–Raduushkevich equations for the calculation of various adsorption parameters. The Freundlich constants n and A were determined as 0.9682 and 0.639 mol/g, respectively. The sorption energy calculated by the Dubinin–Raduushkevich equation was found to be 1.22 kJ/mol. The adsorption behaviour of the dye was also investigated in terms of added cations and anions. It was found that the dye adsorption decreased considerably in the presence of thiosulphate, potassium, nickel and zinc ions.

Mercury volatilisation and phytoextraction from base-metal mine tailings

Experiments were carried out in plant growth chambers and in the field to investigate plant-mercury accumulation and volatilisation in the presence of thiosulphate (S 2O 3)-containing solutions. Brassica juncea (Indian mustard) plants grown in Hg-contaminated Tui mine tailings (New Zealand) were enclosed in gastight volatilisation chambers to investigate the effect of ammonium thiosulphate ([NH 4] 2S 2O 3) on the plant-Hg volatilisation process. Application of (NH 4) 2S 2O 3 to substrates increased up to 6 times the Hg concentration in shoots and roots of B. juncea relative to controls. Volatilisation rates were significantly higher in plants irrigated only with water (control) when compared to plants treated with (NH 4) 2S 2O 3. Volatilisation from barren pots (without plants) indicated that Hg in tailings is subject to biological and photochemical reactions. Addition of sodium thiosulphate (Na 2S 2O 3) at 5 g/kg of substrate to B. juncea plants grown at the Tui mine site confirmed the plant growth chambers studies showing the effectiveness of thio-solutions at enhancing shoot Hg concentrations. Mercury extraction from the field plots yielded a maximum value of 25 g/ha. Mass balance studies revealed that volatilisation is a dominant pathway for Hg removal from the Tui mine site. A preliminary assessment of the risks of volatilisation indicated that enhanced Hg emissions by plants would not harm the local population and the regional environment.

Mediation of arsenic oxidation by Thiomonas sp. in acid-mine drainage (Carnoulès, France).

To isolate, identify, and characterize heterotrophic bacteria in acid-mine drainage that mediate oxidation of As(III). Samples of acid-mine drainage were collected over a period of 14 months. Heterotrophic and non-obligatory acidophilic bacteria in the samples were cultured on a solid medium (pH 7.0-7.2), and three strains were isolated. The three different strains belong to the genus Thiomonas, and have more than 99% homology with the group Ynys1. Culturing in mineral media demonstrated that the isolated strains used thiosulphate as an energy source, and oxidized iron in the presence of thiosulphate. However, none of the strains were able to oxidize arsenic in the presence of thiosulphate, nor could they use iron or arsenic alone as an energy source. In vitro experiments demonstrated that two of the Thiomonas strains were able to oxidize more than 90% of the As(III) present in the acid-mine drainage, whereas no abiotic oxidation of arsenic occurred. Two strains of newly identified Thiomonas sp. found in acid-mine drainage are capable of oxidizing arsenic. These results represent the first reported oxidation of arsenic by Thiomonas sp. Biologically mediated oxidation and subsequent immobilization of arsenic is of great interest for the remediation of contaminated mine sites.

Preg-robbing phenomena in the thiosulphate leaching of gold ores

The ability of various sulphide and gangue minerals and gold ores to adsorb gold during thiosulphate leaching was examined. The effect of free thiosulphate concentration, metal species, gold thiosulphate concentration, ammonia concentration, particle size and cupric addition on preg-robbing was examined in detail, and likely preg-robbing mechanisms were proposed as well. It was found that all the gold ores were highly preg-robbing in thiosulphate deficient systems and that the preg-robbing process was fairly fast. The presence of free thiosulphate could greatly decrease or eliminate preg-robbing in both mineral and gold ore systems, depending on its concentration. Physical adsorption of gold was reversible in the presence of thiosulphate. Lead and zinc ions could reduce gold adsorption to some extent, and competitive adsorption of the gold thiosulphate with the lead and zinc thiosulphate species on the minerals or ores was expected. The gold elution tests demonstrated that preg-robbing was dominated by physical adsorption for the gangue minerals and was controlled by both chemical and physical adsorption for the sulphide minerals. The ability of an ore to adsorb the gold thiosulphate species from solution was found to be intimately associated with the free thiosulphate concentration. Surface topological studies by SEM coupled with EDS showed that gold was adsorbed at defect sites on the surfaces of the minerals.

Studies on the in situ physiology of Thiothrix spp. present in activated sludge.

The in situ physiology of the filamentous sulphur bacterium Thiothrix spp. was investigated in an industrial wastewater treatment plant with severe bulking problems as a result of overgrowth of Thiothrix. Identification and enumeration using fluorescence in situ hybridization (FISH) with species-specific 16S and 23S rRNA probes revealed that 5-10% of the bacteria in the activated sludge were Thiothrix spp. By using a combination of FISH and microautoradiography it was possible to study the in situ physiology of probe-defined Thiothrix filaments under different environmental conditions. The Thiothrix filaments were very versatile and showed incorporation of radiolabelled acetate and/or bicarbonate under heterotrophic, mixotrophic and chemolithoautotrophic conditions. The Thiothrix filaments were active under anaerobic conditions (with or without nitrate) in which intracellular sulphur globules were formed from thiosulphate and acetate was taken up. Thiothrix-specific substrate uptake rates and growth rates in activated sludge samples were determined under different conditions. Doubling times of 6-9 h under mixotrophic conditions and 15-30 h under autotrophic conditions were estimated. The key properties that Thiothrix might be employing to outcompete other microorganisms in activated sludge were probably related to the mixotrophic growth potential with strong stimulation of acetate uptake by thiosulphate, as well as stimulation of bicarbonate incorporation by acetate in the presence of thiosulphate.

Identification of a major facilitator protein from Escherichia coli involved in efflux of metabolites of the cysteine pathway

A chromosomal fragment has been identified in a gene bank from Escherichia coli, which augmented the yield of cysteine in an industrial production strain. Subcloning and genetic analysis showed that an open reading frame coding for a product of 299 amino acids (Orf299) was responsible. Orf299 was synthesized in the T7 polymerase/promoter system and exhibited the properties of an integral membrane protein. Mutational interruption of orf299 did not cause a distinct phenotype; however, transformants overexpressing orf299 had lost the ability to grow in minimal medium unless it was supplemented with a source of reduced sulphur compounds, and they excreted considerable amounts of cysteine and O-acetyl-L-serine, especially in the presence of thiosulphate. Most of the cysteine was found to be masked in 2-methyl-2,4-thiazolidinedicarboxylic acid. N-acetyl-L-serine was also present in the medium, but it is open to question whether it represents a primary excretion product. Measurement of the induction status of the cysteine regulon by means of a cysK'-'lacZ gene fusion demonstrated that the regulon is not induced upon growth in the presence of a poor sulphur source and that the introduction of a constitutive cysB allele alleviates this deficiency. The results indicate that orf299 codes for an export pump for different metabolites of the cysteine pathway. Its relation to other efflux systems and the physiological role are discussed.

Stress corrosion cracking of 13% Cr martensitic steels in sodium chloride solutions in the presence of thiosulphate

The stress corrosion cracking (SCC) susceptibility of 13% Cr martensitic (UNS S42000) and supermartensitic (UNS S41125) steels in sodium chloride solutions in the presence of thiosulphate was evaluated by slow strain rate tests (SSRT). The tests were performed in 5% sodium chloride solutions buffered at pH 2.7, 3.5, 4.5 and 6.0 in the absence and presence of thiosulphate in a concentration range between 10−6 and 10−3 M, at 25 ± 0.1 °C. The electrochemical behaviour of the two steels in the different solutions was determined by recording the anodic and cathodic polarisation curves. 13% Cr martensitic steel showed SCC in 5% sodium chloride solutions with pH ≤ 4.5 in the presence of 3 × 10−6 M thiosulphate. Decreasing the chloride ion concentration from 50 to 10 g/l, the critical concentration of thiosulphate to provoke SCC susceptibility increased from 3 × 10−6 to 1 × 10−5 M. The resistance to SCC of the supermartensitic steel was higher than that of the martensitic steel. The critical concentration of thiosulphate to induce SCC on the supermartensitic steel were 1 × 10−5 M at pH 2.7 and 1 × 10−4 M at pH 3.5. At pH ≥ 4.5 the supermartensitic steel did not crack. The anodic and cathodic polarisation curves evidenced the influence of the thiosulphate on the corrosion and the activation effect on the steels. The SCC of the two steels was attributed to hydrogen embrittlement produced by sulphur and hydrogen sulphide formed by dismutation and reduction of thiosulphate. Spannungsrisskorrosion von martensitischen Stählen mit 13% Chrom in Natriumchloridlösungen bei Anwesenheit von Thiosulfat Die Spannungsrisskorrosionsempfindlichkeit von martensitischen (UNS S42000) und supermartensitischen (UNS S41125) Stählen mit 13% Chrom in Natriumchloridlösungen bei Anwesenheit von Thiosulfat wurde mittels Versuchen mit langsamer Dehngeschwindigkeit untersucht. Die Versuche wurden in 5%igen gepufferten Natriumchloridlösungen bei pH 2,7, 3,5, 4,5 und 6,0 ohne und mit Thiosulfat im Konzentrationsbereich von 10−6 bis 10−3 M bei 25 ± 0,1 °C durchgeführt. Das elektrochemische Verhalten der beiden Stähle in den verschiedenen Lösungen wurde durch Aufnahme von anodischen und kathodischen Polarisationskurven bestimmt. Der martensitische Stahl mit 13% Chrom zeigte Spannungsrisskorrosion in den 5%igen Natriumchloridlösungen bei pH-Werten ≤ 4,5 bei Anwesenheit von 3 × 10−6 M Thiosulfat. Durch Reduzierung der Chloridionenkonzentration von 50 auf 10 g/l steigt die kritische Thiosulfatkonzentration zur Auslösung der Spannungsrisskorrosionsempfindlichkeit von 3 × 10−6 auf 1 × 10−5 M. Der Spannungsrisskorrosionswiderstand des supermartensitischen Stahles war höher als der des martensitischen Stahles. Die kritische Thiosulfatkonzentration zur Einleitung von Spannungsrisskorrosion am supermartensitischen Stahl betrug 1 × 10−5 bei pH 2,7 und 1 × 10−4 bei pH 3,4. Bei pH-Werten ≥ 4,5 traten am supermartensitischen Stahl keine Risse auf. Die anodischen und kathodischen Polarisationskurven bewiesen den Einfluss des Thiosulfates auf die Korrosion und den Aktivierungseffekt der Stähle. Die Spannungsrisskorrosion der beiden Stähle ist auf Wasserstoffversprödung zurückzuführen, die durch Schwefel und durch Reduktion von Thiosulfat gebildeten Schwefelwasserstoff hervorgerufen wird.

SCC inhibition of a C-steel in acidic 5% NaCl solutions in the presence of thiosulphate

The inhibiting effect of some organic compounds on the stress corrosion cracking (SCC) of a C-steel in 5% NaCl+0.5% acetic acid in the presence of 1 mM thiosulphate at 25°C was studied. The examined compounds at 0.1 mM concentration were: n-dodecylquinolinium bromide (DDQB), n-dodecylpyridinium chloride (DDPC), benzyl,stearyl,dimethylammonium chloride (BSDMAC), 1-(2-amminoethyl)-2 n-tridecyl-3 imidazoline (IMI-13), 2- n-hexyl-3 imidazoline (IMI-6), 2- n-tridecyl-3-imidazoline (IMI), N-phenyl-cinnamyliden-imine (PH-ATC). The inhibition of these compounds on the uniform corrosion was evaluated by recording anodic and cathodic polarisation curves after 1 and 24 h immersion of the electrode in the aggressive solutions. Slow strain rate tests were performed at a strain rate of 1×10 −6 s −1. The SCC susceptibility degree ( α) was evaluated by the ratio between percentage elongation to fracture in the test solution and that in air. The hydrogen permeation currents after 24 h of immersion of steel were determined. The examined compounds exerted an inhibiting action towards the general corrosion, ranging between 74 and 96%. The percentage inhibiting efficiencies (IE), calculated from the permeation current values of DDQB, DDPC and IMI, were almost the same as the percentage IE towards the general corrosion. In the presence of the other compounds percentage IE on the hydrogen permeation was lower than that towards the general corrosion. DDQB, DDPC and IMI were able to reduce the stimulating action of thiosulphate completely. The other compounds increased α values, but they were unable to inhibit SCC completely. The inverse linear relationship between α and hydrogen permeation current values evidenced a strict correlation between hydrogen permeation and SCC susceptibility in these solutions.

Effect of thiosulphate as electron acceptor on glucose and xylose oxidation by Thermoanaerobacter finnii and a Thermoanaerobacter sp. isolated from oil field water

During glucose and xylose fermentation, Thermoanaerobacter finnii was observed to produce lactate, acetate, H 2 and CO 2, with ethanol being the major end product. Thermoanaerobacter strain SEBR 5268, an isolate from an oil field, also produced a similar range of end product from glucose and xylose fermentation, with the exception that both ethanol and lactate were the major products of sugar metabolism. Both these strains were able to reduce thiosulphate to sulphide in the presence of these two substrates, with acetate being the dominant metabolite in that case. In addition, a faster growth rate and increased cell yield were obtained in the presence of thiosulphate, than in its absence. The higher concentrations of acetate produced in the presence of thiosulphate rather than without any electron acceptor indicated that more ATP was generated from substrate-level phosphorylation. These results have implications for our understanding of the breakdown of carbohydrates present in organic matter found in the natural ecological niches of Thermoanaerobacter species (sulphide-, elemental sulphur- or sulphate-rich thermal hot springs and oil fields).

5366092 Separation of valuable minerals from material found in the beds of bodies of water

The ability of various sulphide and gangue minerals and gold ores to adsorb gold during thiosulphate leaching was examined. The effect of free thiosulphate concentration, metal species, gold thiosulphate concentration, ammonia concentration, particle size and cupric addition on preg-robbing was examined in detail, and likely preg-robbing mechanisms were proposed as well.It was found that all the gold ores were highly preg-robbing in thiosulphate deficient systems and that the preg-robbing process was fairly fast. The presence of free thiosulphate could greatly decrease or eliminate preg-robbing in both mineral and gold ore systems, depending on its concentration. Physical adsorption of gold was reversible in the presence of thiosulphate. Lead and zinc ions could reduce gold adsorption to some extent, and competitive adsorption of the gold thiosulphate with the lead and zinc thiosulphate species on the minerals or ores was expected.The gold elution tests demonstrated that preg-robbing was dominated by physical adsorption for the gangue minerals and was controlled by both chemical and physical adsorption for the sulphide minerals. The ability of an ore to adsorb the gold thiosulphate species from solution was found to be intimately associated with the free thiosulphate concentration. Surface topological studies by SEM coupled with EDS showed that gold was adsorbed at defect sites on the surfaces of the minerals.

Determination of microgram and nanogram amounts of active chlorine in water by iodine—azide reaction induced by thiosulphate or thioammeline

An indirect determination of active chlorine in water based on the induced iodine—azide reaction and measuring the amount of thiosulphate or thioammeline oxidized by chlorine is described. The oxidation products do not induce the iodine—azide reaction. The decrease in the amount of thiosulphate or thioammeline taken in excess with respect to chlorine is proportional to the amount of chlorine in the sample. Three procedures for the determination of chlorine based on this principle were applied: back-titration of an excess of iodine in the reaction medium, titration with an iodine solution which is very slowly added to the sample solution at a constant rate and continuous-flow determination. The concentration ranges for the determination of chlorine are by back-titration 1–12 μg or 0.1–0.7 μg in a 5-ml sample in the presence of thiosulphate or thioammeline, respectively, by titration with iodine solution 3–20 ng in a 10-ml sample in the presence of thioammeline and by continuous-flow determination from 0.5–5 μg l −1 to 0.05–1.5 mg l −1 depending on the reaction conditions and the inductor applied.

Growth of Anacystis in the Presence of Thiosulphate and its Consequences for the Architecture of the Photosynthetic Apparatus

AbstractWith the aim of obtaining information on the degree of flexibility maintained in cyanobacteria in context with their phylogenetic position, Anacystis was grown in the presence of thiosulphate, oxidized in a photosystem I (PSI) dependent reaction (KM 7.4 × 10−3 M thiosulfate). Besides DBMIB, only o‐phenanthroline and p‐hydroxymercuribenzoate blocked thiosulphate‐dependent PSI activity to some extent; iodonitrothymol, DCMU and cyanide had no influence. Growth of Anacystis in the presence of thiosulphate induced a reorganization of the photosynthetic apparatus characterized by a shift in the PSII/PSI ratio in favor of PSI, comparable to low light conditions. Capability for oxygenic photosynthesis never completely disappeared; structural elements of PSII were retained in the membrane to a certain degree. The antenna pigment system signalled high light under conditions of thiosulphate oxidation as judged from the ratio of phycocyanin to chlorophyll. Besides a shift in the ratio of PSII to PSI components, the polypeptide pattern of thylakoids from thiosulphate grown cells shows several additional components compared to the controls and, moreover, higher concentrations of some polypeptides present in the controls, particularly a Mr 41000 polypeptide. The process of thiosulphate oxidation appears bound to the thylakoid membrane.

Sulphidolysis of pentathionate and spectrophotometric determination of pentathionate, thiosulphate and sulphide in their mixtures

A spectrophotometric method has been developed for the determination of pentathionate in a mixture with thiosulphate and sulphide. The conditions for pentathionate to be stoicheiometrically converted into thiosulphate were established by varying the reaction time, pH and amount of sulphide. The excess of sulphide used for the sulphidolysis of pentathionate was removed with a suspension of freshly precipitated zinc carbonate hydroxide. The proposed method was successfully applied to the determination of pentathionate, thiosulphate and sulphide mixed in various ratios and gave a relative standard deviation of 0.89% for pentathionate at the 1 µmol level in the presence of thiosulphate (2 µmol) and sulphide (1 µmol).