Sulfur sulfites

SULFUR (In Biological Systems). Sulfur, in some form, is required by all living organisms. It is utilized in various oxidation stales, including sulfide, elemental sulfur, sulfite, sulfate, and thiosulfate by lower forms and in organic combinations by all. The more important sulfur-containing organic compounds include the amino acids (cysteine, cystine, and methionine, which are components of proteins) the vitamins thiamine and... 

Autoxidation of aqueous H2S solutions results in elemental sulfur, sulfite, thiosulfate, and eventually sulfate. However, under certain conditions monodispersed sulfur sols with particle diameters of between 0.2 and 1.2 /um are obtained [48]. For example, a solution of H2S of concentration 46 mmol 1 in pure H2O exposed to air at 25 °C became turbid after an induction period of ca. 8 h and then showed briUiant higher-order Tyndall spectra. A solution saturated in H2S exhibited a pH value of 4.1 and was rapidly oxidized in an atmosphere of pure O2. At pH values >8 no elemental sulfur was formed (clear colorless solution), in the range pH=7-8 yellow solutions were obtained (polysulfide anions), while at pH<7 turbid solutions were produced but the induction period was as longer as lower the pH value [48] ... 

SULFIDAL (7704-34-9) see sulfur. SULFITE CELLULOSE (9004-34-6) (C6H2 05), Combustible solid. Fine dust can... 

Note in the above list the spelling of the halogens, cesium and sulfur f is used in the place of ph in all derivatives of sulfur (as sulfuric, sulfite, sulfo-, etc.). -... 

Dissimilatory sulfate reducers—cannot reduce sulfates Capable of reducing elemental sulfur, sulfite, and thiosulfate... 

Incompatibilities and Reactivities Peroxides, oxides of phosphorous, organics, virater [Note Decomposes violently In water to form hydrochloric acid, sulfur dioxide, sulfur, sulfite, thiosulfate, and hydrogen sulfide. Corrosive to metals.] ... 

At the anode, a chemical oxidation reaction is bound to take place. In normal fixers, sulfite (SOj ) is oxidized and acid (H ) is released as a consequence of this oxidation. Due to the decrease of the sulfite concentration and the decrease in the pH, the fixing solution becomes unstable and sulfur precipitation starts to occur when the pH of the fixer decreases below 4.0. In the case of hardening fixers, there is also an upper limit to the pH, since aluminum-hydroxides starts to precipitate when the pH exceeds 5.0. 

Polythiodipropionic acids and their esters are prepared from acryUc acid or an acrylate with sulfur, hydrogen sulfide, and ammonium polysulfide (32). These polythio compounds are converted to the dithio analogs by reaction with an inorganic sulfite or cyanide. 

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, siUcon, and sulfur are not included these are of interest, however, because of their stabiUty at high temperatures. A large number of ternary compounds, including numerous oxyhaUdes, and more compHcated compounds have been synthesized and characterized. These include many intermediate (nonstoichiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teUurates, tellurites, selenides, and teUurides. 

Sulfur Dioxide and Sulfites. Sulfur dioxide [7446-09-5], SO2, sodium bisulfite [15181-46-1], NaHSO, and sodium metabisulfite [23134-05-6] ate effective against molds, bacteria, and certain strains of yeast. The wine industry represents the largest user of sulfites, because the compounds do not affect the yeast needed for fermentation. Other appHcations include dehydrated fmits and vegetables, fmit juices, symps and concentrates, and fresh shrimp (79). Sulfites ate destmctive to thiamin, and cannot be used in foods, such as certain baked goods, that ate important sources of this vitamin. 

Reduction of metal oxides with hydrogen is of interest in the metals refining industry (94,95) (see Metallurgy). Hydrogen is also used to reduce sulfites to sulfides in one step in the removal of SO2 pollutants (see Airpollution) (96). Hydrogen reacts directiy with SO2 under catalytic conditions to produce elemental sulfur and H2S (97—98). Under certain conditions, hydrogen reacts with nitric oxide, an atmospheric poUutant and contributor to photochemical smog, to produce N2 ... 

Alkali Fusion of /u-Benzenedisulfonic Acid. Even though this process like the previous one is a very ancient one, it is still the main route for the synthesis of resorcinol. It has been described in detail previously and does not seem to have drastically evolved since 1980. It involves the reaction of benzene with sulfuric acid to form y -benzenedisulfonic acid which is then converted to its disulfonate sodium salt by treatment with sodium sulfite. In a second step, this salt is heated to 350°C in the presence of sodium hydroxide yielding the sodium resorcinate and sodium sulfite. 

After sulfuric acid work-up (accompanied by the formation of sodium sulfate), the resorcinol is extracted and isolated in a 94% yield based on y -benzenedisulfonic acid [98-48-6]. In addition to the technical complexity that goes along with the manipulation of soHds at high temperature, this process produces large amounts of salts (sulfite and sulfate salts) which economically as well as environmentally are not always desired. 

Lead shows excellent resistance to phosphoric and sulfuric acid in almost all concentrations and at elevated temperatures, as well as to sulfide, sulfite, and sulfate solutions. The corrosion film is insoluble lead sulfate which rapidly reforms if it is damaged. Lead is also resistant to chlorides, fluorides, and bromates at low concentrations and low temperatures. However, because lead is soluble in nitric and acetic acids, it is not resistant to these acids. 

The lignitic coals of the northern United States tend to have low sulfur contents, making them attractive for boilet fuels to meet sulfur-emission standards. However, low sulfur content coals have impaired the performance of electrostatic precipitators. The ash of these coals tends to be high in alkaline earths (Ca, Mg) and alkaUes (Na, K). As a result, the ash can trap sulfur as sulfites and sulfates (see Airpollution control methods). 

Deficiency or Toxicity in Humans. Molybdenum deficiency in humans results in deranged metaboHsm of sulfur and purines and symptoms of mental disturbances (130). Toxic levels produce elevated uric acid in blood, gout, anemia, and growth depression. Faulty utiH2ation results in sulfite oxidase deficiency, a lethal inborn error. 

Sulfur Compounds. Aqueous sulfide and H2S, an odiferous compound in some waters, are oxidized rapidly (initially to sulfite and sulfurous acid) the rate constants ate 3x10 and 3 X 10 , respectively. Thiocyanate is oxidized by ozone to cyanide and sulfate via the intermediate formation of sulfite (47). 

Sulfite is oxidized rapidly (/t = 1 X 10 ) to sulfate by ozone (39). Bisulfite ion and sulfurous acid also are oxidized rapidly (to bisulfate and sulfuric acid) with k values of 3.2 X 10 and 2 X 10 , lespectively. 

Ammonium Sulfite—Sodium Chloride Process. Ammonium chloride has been produced by the reaction of ammonium sulfite [10196-04-0] NH SO, and sodium chloride ia a large Canadian plant (14). Ammonium sulfite is never actually isolated, rather ammonia and sulfur dioxide react ia water with sodium chloride. 

Includes hydrogen, sulfur, batteries, chemicals, and spent sulfite Hquor. 

At room temperature, the bisulfite pH inflection poiat occurs at pH 4.5 and the monosulfite at pH 9. Analogous equations can be written for magnesium, calcium, and ammonia. The starting raw materials, ia addition to sulfur, are sodium hydroxide, magnesium oxide, calcium carbonate, or ammonia, depending on the base used. The four commercial bases used ia the sulfite process are compared ia Table 4. 

Chemical recovery ia sodium-based sulfite pulpiag is more complicated, and a large number of processes have been proposed. The most common process iavolves liquor iaciaeration under reduciag conditions to give a smelt, which is dissolved to produce a kraft-type green liquor. Sulfide is stripped from the liquor as H2S after the pH is lowered by CO2. The H2S is oxidized to sulfur ia a separate stream by reaction with SO2, and the sulfur is subsequendy burned to reform SO2. Alternatively, ia a pyrolysis process such as SCA-Bidemd, the H2S gas is burned direcdy to SO2. A rather novel approach is the Sonoco process, ia which alumina is added to the spent liquors which are then burned ia a kiln to form sodium aluminate. In anther method, used particulady ia neutral sulfite semichemical processes, fluidized-bed combustion is employed to give a mixture of sodium carbonate and sodium sulfate, which can be sold to kraft mills as makeup chemical. 

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