Sulfite from thiosulfate

Ana.lytica.1 Methods. Various analytical methods involve titration with oxidants, eg, hexacyanoferrate (ferricyanide), which oxidize dithionites to sulfite. lodimetric titration to sulfate in the presence of formaldehyde enables dithionite to be distinguished from sulfite because aldehyde adducts of sulfite are not oxidized by iodine. Reductive bleaching of dyes can be used to determine dithionite, the extent of reduction being deterrnined photometrically. Methods for determining mixtures of dithionite, sulfite, and thiosulfates have been reviewed (365). Analysis of dithionite particularly for thiosulfate, a frequent and undesirable impurity, can be done easily by Hquid chromatography (366). 

The scheme (Fig. 15.1) thus explained the production of both sulfate and sulfur in equimolar amounts from thiosulfate oxidation. In showing adenylylsulfate as an intermediate, it also provided a feasible route for the conservation of energy from sulfite oxidation by a substrate-level phosphorylation mechanism, in which ADP sulfurylase and adenylate kinase give rise to ATP ... 

An important property of 3-mercaptopyruvate arises from electron withdrawal by the carbonyl group. This makes the SH group electrophilic and able to be transferred as SH+, S°, to a variety of nucleophiles (Eq. 24-44). Thus sulfite yields thiosulfate (S2032 + H+, Eq. 24-45, step a), cyanide yields thiocyanate (Eq. 24-45, step b), and cysteine sulfinate yields alanine thiosulfonate.448 461 The reactions are catalyzed by mercaptopyruvate sulfurtransferase, an enzyme very similar to thiosulfate sulfurtransferase. The latter is a liver enzyme often called by the traditional... 

Dilute acids precipitate sulfur from thiosulfates (difference from sulfides and sulfites),... 

The critical step in the use of multiple sulfur linkages is the availability of HS" from the reduced enzyme system. The HS" could possibly attack the cyclic or the acyclic multiple sulfur linkages through a nucleophilic mechanism. The cleaved sulfide linkages undergo oxidation to sulfite or thiosulfate. This seems a plausible pathway for the oxidation of the sulfur compounds in the present study. 

Figure 2. Radioactivity chromatogram of sulfur compounds derivatized with monobromobimane. The reversed-phase HPLC separation is based on the hydrophobic properties of the bimane-sulfur adducts but peak area is based on "S-radioactivity of the compounds. At time 0 sulfite and thiosulfate impurities are present before addition of the hepatopancrease tissue homogenate. This was a 60 min experiment to determine the sulfide detoxifying functions of the hepatopancrease of the hydrothermal vent crab Bythograea thermydron. During this time the proportion of radioactivity in sulfide rapidly decreases and thiosulfate and sulfate accumulate as end products. Two intermediates, pi and p2 accumulate then decrease during the experiment. The two intermediates are believed to be polysulfides based on similar elution times of polysulfide standards. (Figure is the unpublished chromatograms from the data in Vetter et al. (24)-) continued on next page.

Anoxyphotobacteria which do not possess a "reverse" sulfite reductase are nevertheless able to form sulfite from sulfide, if they contain a flavocytochrome and a thiosulfate reductase. Therefore Trueper and Fischer (22) assume that in these organisms the following reaction mechanism might be possible ... 

Sulfur can be effectively removed from a compound, organic or inorganic, by contact with Raney nickel. The action has been described by Aubry (118) as being noncatalytic in nature. One atom of sulfur is removed from sodium thiosulfate in the cold, yielding sodium sulfite from which the sulfur can be completely removed at 100°. Although sulfur can be completely removed from stannous sulfide, it can be only partially removed from antimony sulfide. Following are some of the inorganic compounds from which sulfur removal by use of Raney nickel has been observed (119). 

To prevent the sulfite from attacking the trisulfane (with formation of thiosulfate and disulfane), the reaction is carried out in the presence of formaldehyde at pH = 7 (see equation 58). Aromatic, aliphatic, and aUcenic trisulfanes have been obtained in this way in high yields. d27... 

The cathodic polarization curves were determined for the reduction of gold ions in solutions containing, respectively, sulfite alone, thiosulfate alone, and a mixture of sulfite and thiosulfate. These curves are shown in Fig. 39. Addition of thiosulfate to the solution of gold sulfite complex shifts the polarization curve to the potential range where the thiosulfate complex is reduced. This result shows that the reduction of gold in the sulfite-thiosulfate mixture takes place from the thiosulfate complex. This conclusion is consistent with the difference between the stability constants of the two complexes ... 

Fig. 40 shows polarization curves obtained from a system containing sulfite alone and one containing both sulfite and thiosulfate, respectively. It is seen that the deposition rate expected from the current at the mixed potential (indicated by arrows) is about ten times higher in the sulfite-thiosulfate mixture than in the solution containing sulfite alone. 

EBMUD, Oakland, CA Combined chlorine Sodium sulfite Sodium thiosulfate Ascorbic acid Tablets from 2 companies Crystals Powder Varied from 1 to 36 tablets 1 lb in nylon bags placed on the flow path 1.2 8.0 Surface water 100-500 100 100... 

When no dechlorination chemical was added, the dissolved oxygen concentration of the released water decreased from an initial concentration of 11 by less than 0.3 mg/L after traveling 450 ft in one test. When stoichiometric amounts of dechlorination chemicals were added, the DO decreased by 1.18,0.3,0.55, and 0.5 mg/L in the presence of sodium metabisulfite, sodium sulfite, sodium thiosulfate, and calcium thiosulfate, respectively. When twice the stoichiometric amounts of dechlorination chemicals were added, the dissolved oxygen concentration decreased hy 1, 0.9, 0.9, and 0.7 mg/L, respectively, in the presence of these chemicals. With the addition of stoichiometric concentrations of ascorbic acid and sodium ascorbate, the DO of the water increased by 0.3 mg/L, after a travel of 450 ft. When twice the stoichiometric concentrations of these chemicals were used, the DO decreased hy 0.2 mg/L. 

A notable feature of the reduction potentials for the four individual reaction steps in Table XXII is that three of the potentials are as low as that of the hydrogen couple, and the fourth is almost as high as in Oz or nitrate respiration. A large part of the total free energy of the sulfate-to-sulfide reaction seems to be concentrated in the trithionate ion so it can be released in one step. It is possible to speculate that the three low potential steps—reduction of sulfate, sulfite, and thiosulfate—are only maintenance level operations, receiving their electrons from a short chain similar to Fig. 41 which produces no ATP. A longer electron transport chain could operate between approximately —450 and -(-381 mV to carry electrons to trithionate, and several ATP could be generated within this potential gap. 

The elemental sulfur becomes colloidally stable in Sg molecules but can also add to sulfite and form thiosulfate S + S (0)3 S - S (0)3 (S203 ), which also loses the sulfur via disproportionation into H2S and SO4 . In hydrometeors and interfacial waters, however, sulfur reacts with oxygen (reactions 5.265 and 5.262) via SO2 to form hydrogen sulfite HSO3. Thiosulfate is an important intermediate in biological sulfur chemistry from both sulfate reduction and sulfide oxidation. Many hypothetical so-called lower sulfuric acids (Table 5.19) might appear as intermediates or in the form of radicals (such as SOH, HSO, HSO2, HSS and HS as seen from the structure formulas) in the oxidation chain from sulfide to sulfate ... 

Thiosulfates also are sometimes used as reducing agents. They result from the reaction of sulfur or a polysulfide with a sulfite. Sodium thiosulfate is widely available in solid form, both anhydrous and as the pentahydrate (the photographer s hypo ). The pentahydrate crystallizes from solutions with concentrations between 30% and 60% Na2S203. The compound is quite soluble in water (33.3% at 0°C from the anhydrous form), and hypo dissolves in its water of hydration at 48°C. All forms are nontoxic under normal conditions and are used as food additives. In addition, Na2S203 forms neutral solutions. While correspondingly easier to handle than NaHS03, it is normally stored in similar equipment. 

Recovery from Elemental Te(169). The tellurium was dissolved in a mixture of chromium(VI) oxide and concentrated sulfuric acid or in one of potassium dichromate and the acid. The periodate formed was reduced to elemental iodine by oxalic acid and the iodine distilled into a solution containing sulfite or thiosulfate. The iodide in solution was oxidized with permanganate and then reduced to the free condition with oxalic acid. The element was again distilled into a reducing solution. Yields up to 90% were obtained. 

Lanthanons are not sorbed to any appreciable extent on anion exchangers from aqueous HCl, HNO3 and H2SO4, and are only weakly sorbed from solutions of salts such as sulfites, sulfates, thiosulfates, nitrates, nitrites and thiocyanates. Marcusa i however, demonstrated that gradient elution,... 

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