Thiosulphate oxidation

The observed orders were, in fact, 1.12 for S208 and 1.08 for Cu and Fe, and these have been taken as unity. Of more significance is the fact that the orders in Cu and Fe, accurately unity above about 2 x 10 and 2 x 10 M respectively, dropped to about 0.5 and 0.6 for lower catalyst concentrations. The activation energies shown in Table 25 were actually determined below the transition region. Direct analysis and the kinetic results agree on a copper content in the solvent used equal to about 10 M. 

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Kelly DP, Syrett PJ 1966b. [35S]Thiosulphate oxidation by Thiobacillus strain C. Biochem J 98 537 5. 

Timmer-Ten Hoor A. (1975) A new type of thiosulphate oxidizing, nitrate reducing microorganism Thiomicrospira denitrificans. Neth. J. Sea Res. 9, 351 -353. 

Lu W-P, Kelly DP (1983a) Rhodanese an enzyme not necessary for thiosulphate oxidation by Thiobacillus A2. FEMS Microbiol Lett 18 289-292... 

Lu W-P, Kelly DP (1983b) Purification and some properties of two principal enzymes of the thiosulphate-oxidizing multi-enzyme system from Thiobacillus A2. J Gen Microbiol 129 3549-3564... 

Lu W-P, Kelly DP (1988a) Cellular location and partial purification of the thiosulphate-oxidizing enzyme and trithionate hydroxylase from Thiobacillus tepidarius. J Gen Microbiol 134 877-885... 

Lu W-P, Kelly DP (1988b) Respiration-driven proton translocation in Thiobacillus versutus and the role of the periplasmic thiosulphate-oxidizing enzyme system. Arch Microbiol 149 297-302... 

Sodium sulphide, NajS, formed by reduction Na2S04 with CO or H2- Aqueous solutions are oxidized to sodium thiosulphate. 

The oxidation of the thiosulphate ion SjOj to tetrathionate ion, is used to estimate iodine. 

I he methyl iodide is transferred quantitatively (by means of a stream of a carrier gas such as carbon dioxide) to an absorption vessel where it either reacts with alcoholic silver nitrate solution and is finally estimated gravimetrically as Agl, or it is absorbed in an acetic acid solution containing bromine. In the latter case, iodine monobromide is first formed, further oxidation yielding iodic acid, which on subsequent treatment with acid KI solution liberates iodine which is finally estimated with thiosulphate (c/. p. 501). The advantage of this latter method is that six times the original quantity of iodine is finally liberated. 

In a 500 ml. three-necked flask, equipped with a thermometer, a sealed Hershberg stirrer and a reflux condenser, place 32-5 g. of phosphoric oxide and add 115-5 g. (67-5 ml.) of 85 per cent, orthophosphoric acid (1). When the stirred mixture has cooled to room temperature, introduce 166 g. of potassium iodide and 22-5 g. of redistilled 1 4-butanediol (b.p. 228-230° or 133-135°/18 mm.). Heat the mixture with stirring at 100-120° for 4 hours. Cool the stirred mixture to room temperature and add 75 ml. of water and 125 ml. of ether. Separate the ethereal layer, decolourise it by shaking with 25 ml. of 10 per cent, sodium thiosulphate solution, wash with 100 ml. of cold, saturated sodium chloride solution, and dry with anhydrous magnesium sulphate. Remove the ether by flash distillation (Section 11,13 compare Fig. II, 13, 4) on a steam bath and distil the residue from a Claisen flask with fractionating side arm under diminished pressure. Collect the 1 4-diiodobutane at 110°/6 mm. the yield is 65 g. 

In order to prepare an acid, a dioxan solution of the diazo ketone is added slowly to a suspension of silver oxide in a dilute solution of sodium thiosulphate Iftheco)iversion to the acid yields unsatisfactory results, it is usually advisable to prepare the ester or amide, which are generally obtained in good yields hydrolysis of the derivative gives the free acid. 

Introduce a solution of 15 g. of the diazo ketone in 100 ml. of dioxan dropwise and with stirring into a mixture of 2 g. of silver oxide (1), 3 g. of sodium thiosulphate and 5 g. of anhydrous sodium carbonate in 200 ml. of water at 50-60°. When the addition is complete, continue the stirring for 1 hour and raise the temperature of the mixture gradually to 90-100°. Cool the reaction mixture, dilute with water and acidify with dilute nitric acid. Filter off the a-naphthylacetic acid which separates and recrys-talhse it from water. The yield is 12 g., m.p. 130°. 

Add, with stirring, a solution of 6 8 g. of the fiis-diazo ketone in 100 ml. of warm dioxan to a suspension of 7 0 g. of freshly precipitated silver oxide in 250 ml. of water containing 11 g. of sodium thiosulphate at 75°. A brisk evolution of nitrogen occurs after 1 5 hours at 75°, filter the liquid from the black silver residue. Acidify the almost colourless filtrate with nitric acid and extract the gelatinous precipitate with ether. Evaporate the dried ethereal extract the residue of crude decane-1 10-dicarboxylic acid weighs 4 -5 g. and melts at 116-117°. RecrystaUisation from 20 per cent, aqueous acetic acid raises the m.p. to 127-128°. 

For the preparation of standard iodine solutions, resublimed iodine and iodate-free potassium iodide should be employed. The solution may be standardised against pure arsenic(III) oxide or with a sodium thiosulphate solution which has been recently standardised against potassium iodate. 

Alternative procedure. The following method utilises a trace of copper sulphate as a catalyst to increase the speed of the reaction in consequence, a weaker acid (acetic acid) may be employed and the extent of atmospheric oxidation of hydriodic acid reduced. Place 25.0 mL of 0.017M potassium dichromate in a 250 mL conical flask, add 5.0 mL of glacial acetic acid, 5 mL of 0.001M copper sulphate, and wash the sides of the flask with distilled water. Add 30 mL of 10 per cent potassium iodide solution, and titrate the iodine as liberated with the approximately 0.1M thiosulphate solution, introducing a little starch indicator towards the end. The titration may be completed in 3-4 minutes after the addition of the potassium iodide solution. Subtract 0.05 mL to allow for the iodine liberated by the copper sulphate catalyst. 

Dithiol is a less selective reagent than thiocyanate for molybdenum. Tungsten interferes most seriously but does not do so in the presence of tartaric acid or citric acid (see Section 17.34). Tin does not interfere if the absorbance is read at 680 nm. Strong oxidants oxidise the reagent iron(III) salts should be reduced with potassium iodide solution and the liberated iodine removed with thiosulphate. 

Silyl enol ethers, 23, 77, 99-117,128 Silyl enolates, 77 Silyl peroxides, 57 Silyl triflate, 94 Silyl vinyl lithium, 11 (E)-l -Silylalk-1 -enes, 8 Silylalumimum, 8 Silylation, 94 reductive, 26 a-C-Silylation, 113 O-Silylation.99,100 / -SilyIketone, 54 non-cydic, 55 Silylmagnesium, 8 Silyloxydienes, 112 Sodium hexamethyldisilazide, 89 Sodium thiosulphate pentahydrate, 59 Stannylation, see Hydrostannylation Stannylethene, 11 (Z)-Stilbene, 70 (E)-Stilbene oxide, 70 /3-Styryltrimethylsilane, 141 Swern oxidation. 84,88... 

Aravamudan and Venkappayya75 oxidized dimethyl sulphoxide in acetate buffer of pH 4 to 4.5 and with a reaction time of only 1 min. They then added potassium iodide and acid and titrated with thiosulphate the iodine liberated by unused reagent. They reported that cerium(IV) and Cr(VI) were much less effective oxidizing reagents for the sulphoxide. A very similar procedure was used by Rangaswama and Mahadevappa76 to determine dimethyl sulphoxide and numerous other compounds with chloramine B. 

Bohme77 employed excess monoperphthalic acid in diethyl ether to oxidize dibenzyl and benzyl ethyl sulphoxides. Reaction time was 24 h at - 15 to + 10 °C, after which he added potassium iodide and water and titrated the iodine set free with thiosulphate. Dickenson78 oxidized dimethyl sulphoxide in malt, wort or beer with Na2S2Os. In... 

The Co(III) complexes Co(NH3)6 " and Co(NH3)sOH bring about oxidation of stannate(II) ion in strongly basic solution . The rates were found to be independent of the concentration of the Co(III) complex. It is proposed that stannate(Il) exists as a dimer, and that the monomer is the reactive species, the rate being close to half-order in stannate(II). Cyanide and thiosulphate catalyse the reaction but Co(CN)g is immune to attack by stannate(II) ion. The experimental difficulties encountered in this study preclude a full analysis as regards mechanism. 

At high ratios of reductant to oxidant, conditions which favour tetrathionate formation at the expense of sulphate, the Cr(Vl) oxidation of thiosulphate follows kinetics ... 

The work with iodide (preceding sub-section) was extended to thiosulphate , and isosbestic points and second-order kinetics were again obtained with the various Pt(IV) complexes (Table 8). Two 8203 ions are consumed per mole of Pt(IV) reduced, suggesting tetrathionate to be the product of oxidation, viz. 

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