A sulfur

Ikemiya N, Miyaoka S and Hara S 1994 Observation of the Cu(1 1) adlayer on Au(111) in a sulfuric acid solution using atomic force microscopy Surf. Sc/. 311 L641-8... 

Sulfur is found in meteorites. R.W. Wood suggests that the dark area near the crater Aristarchus is a sulfur deposit. 

In the synthesis of commercial sulfur-heterocycles two interesting reactions are used (i) diphenylamines may be connected by a sulfur bridge in the orfho-positions (ii) the amino grouping of sulfonamides undergoes condensation reactions with neighboring imino- and amide groups. 

Thioacetyl derivatives (155) are obtained by direct heterocyclization reactions (365. 378, 563) and by a sulfur-oxygen exchange" reaction involving thioacetic acid and A-2-oxazoline-5-one (154) or A-2-thiazoline-5-one (156) (Scheme 81) (365, 378, 379). Ra-Ni reduction of 155 affords the 5-unsubstituted thiazole (379). 

The formation of a sulfur-containing ring was justified by the attack of the halogenated carbon of the cMoroacetyl derivative by the sulfur atom of thiourea, a fact in accordance with the results just discussed by Wallach (49,50) and Claus (51). The new formula (37) of thiohydantoine explained why, contrary to thiourea, its desulfuration was difficult. 

In 1888, Foerster (91), reproducing the same reaction with dianisyl-thiourea, demonstrated that the compound he obtained (59) could lose a sulfur atom by reduction with tin and hydrochloric acid to form a product analogous to N-phenylpiperidine (60). 

Section 20 13 Thioesters undergo reactions analogous to those of esters but at faster rates A sulfur atom stabilizes a carbonyl group less effectively than an oxygen... 

After cleaning to remove coarse material, ie, cobs, and fines (broken com, dust, etc), the com is steeped in a sulfurous acid solution to soften the com and render the starch granules separable from the protein matrix that envelopes them. About 7% of the kernel s dry substance is leached out during this step, forming protein-rich steep-water, a valuable feed ingredient and fermentation adjunct. 

Total Sulfur and Sulfide Sulfur. Total sulfur is predominately in the form of metal sulfate, and because sulfates act as inerts, these materials have htde impact on the process. Sulfide sulfur compounds, on the other hand, react and leave the furnace as a sulfur vapor, which may deposit in the gas handling system. A possible mechanism for this is the partial reaction of SO2 to H2S, followed by... 

Ranitidine. Ranitidine hydrochloride [66357-59-3] (Zantac) is a white to pale yellow granular substance. It is freely soluble in water and acetic acid, soluble in methanol, sparingly soluble in ethanol, and practically insoluble in chloroform. It has a slightly bitter taste and a sulfur-fike odor. It may be made by the method described in Reference 5. 

Thiomahc acid [70-49-5] (mercaptosuccinic acid), C H O S, mol wt = 150.2, is a sulfur analogue of malic acid. The properties of the crystalline, soHd thiomalic acids ate given in Table 6. The racemic acid has the following acid dissociation constants at 25°C pTf i — 3.30 pffc2 — 4.94. 

Owing to the cycHc nature of the TBRC operation, waste heat recovery from the off-gases is not practical and the SO2 content of the gas varies with the converter cycle. In order to supply a relatively uniform flow and strength SO2 gas to a sulfuric acid plant, a system has been installed at RonnskAr whereby the SO2 from fluctuating smelter gases is partially absorbed in water. During smelter gas intermption, SO2 is stripped with air and the concentrated gas deflvered to the acid plant. 

The potassium combines with the sulfur to form potassium sulfate, which condenses as a soHd primarily in the electrostatic precipitator (ESP) or baghouse. The recovered potassium sulfate is then deUvered to a seed regeneration unit where the ash and sulfur are removed, and the potassium, in a sulfur-free form such as formate or carbonate, is recycled to the MHD combustor. It is necessary also to remove anions such as Cf and E which reduce the electrical conductivity of the generator gas flow. These are present in the coal ash in very small and therefore relatively harmless concentrations. As the seed is recycled, however, the concentrations, particularly of CF, tend to build up and to become a serious contaminant unless removed. 

The quahty of naphthalene required for phthaUc anhydride manufacture is generally 95% minimum purity. The fixed plants do not require the high (>98%) purity naphthalene product and low (<50 ppm) sulfur. The typical commercial coal-tar naphthalene having a purity ca 95% (freezing point, 77.5°C), a sulfur content of ca 0.5%, and other miscellaneous impurities, is acceptable feedstock for the fixed-bed catalyst process based on naphthalene. 

The products resulting from such reactions should, therefore, have analogous names. If KBO2 is a borate, KBS2 is a thioborate and KBF is a fluoroborate. Similarly, the replacement of an oxygen atom by a sulfur atom or two fluorine atoms is understandable. However, the relationship of K2BN2 is less obvious, until one considers the dehydration and deammoniation schemes ... 

Fig. 2. Distribution of compounds as a function of cmde oil boiling point (a) sulfur where A, B, and C represent high (>2%), medium (ca 1.5%), and low (<0.1%) sulfur, respectively, and (b) nitrogen, where A and B represent high (ca 0.5%) andlow (<0.1%) nitrogen, respectively.

The saturated, cleaned raw synthesis gas from a Texaco partial oxidation system is first shifted by use of a sulfur resistant catalyst. Steam required for shifting is already present ia the gas by way of the quench operation ia the generator. The shifted gas is then processed for hydrogen sulfide and carbon dioxide removal followed by Hquid nitrogen scmbbiag. 

A variation on ofloxacin is mfloxacin (20) this compound lacks the methyl group on the 1,8-bridge and contains a sulfur in place of the oxygen attached to the 8-position. Rufloxacin, although less potent than ofloxacin, is well absorbed and has longer half life than does ofloxacin (44—46). 

Semichemical pulping can be accompHshed by a sulfur-free system of sodium hydroxide and sodium carbonate. The sodium carbonate is recovered by simple incineration, and sodium hydroxide is added as makeup. Advantages in recovery operation are obtained if potassium hydroxide is added occasionally to maintain ca 20 mol % potassium carbonate (66). Lastiy, semichemical pulping can be accompHshed by using kraft white Hquor of low strength. 

Chloroprene Elastomers. Polychloroprene is a polymer of 2-chloro-l,3-butadiene. The elastomer is largely composed of the trans isomer. There are two basic polymer types the W-type and the G-type. G-types are made by using a sulfur-modified process W-types use no sulfur modification. As a result, G-types possess excellent processing and dynamic properties, and tend to be used in V-belts. However, they have poorer aging properties than W-types. The W-types tend to be used in appHcations requiring better aging, such as roUs and mechanical goods (see Elastomers, SYNTHETIC-POLYCm.OROPRENE). 

Thiosahcyhc 2Lcid[147-93-3] (o-mercaptobenzoic acid), a sulfur-yeUow sohd that softens at 158°C, has a melting point of 164°C. It sublimes, is slightly soluble in hot water but freely soluble in glacial acetic acid and alcohol, and yields dithiosahcyhc acid [527-89-9] upon exposure to air. 

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