Sulfur compounds formed from

Volatile sulfur compounds are found in most cheeses and can be important flavor constituents. The origin of sulfur-containing compounds is generally thought to be the sulfur-containing amino acids methionine and cysteine (Law, 1987). As Cys is rare in the caseins (occurring at low levels only in Os2- and K-caseins, which are not extensively hydrolyzed in cheese), the origin of sulfur compounds must be primarily Met. Sulfur compounds formed from Met include H2S, dimethylsulfide, and methanethiol. The importance of methanethiol and related compounds in cheese aroma is discussed by Law (1987). 

Table I. Sulfur Compounds Formed from Methionine and Riboflavin during Light Irradiation under Acidic Conditions.

The ratio of hydrogen to carbon monoxide is controlled by shifting only part of the gas stream. After the shift, the carbon dioxide, which is formed in the gasifier and in the water gas reaction, and the sulfur compounds formed during gasification, are removed from the gas. 

Organic acids, including carbon dioxide, lower the wort pH during fermentation. The principal acids formed are lactic, pymvic citric, malic, and acetic acids, at concentrations ranging from 100—200 ppm. The main sulfur compounds formed during fermentation and thek perception thresholds are as follows H2S (5—10 ppb) ethanethiol (5—10 ppb) dimethyl sulfoxide (35—60 ppb) and diethyl sulfide (3—30 ppb). At low levels, these may have a deskable flavor effect at higher levels they are extremely undeskable. Sulfur dioxide also forms during fermentation, at concentrations of 5—50 ppm its presence can be tasted at levels above 50 ppm. 

Identify the ionic compounds formed from the following elements (a) calcium and fluorine (b) lithium and oxygen (c) magnesium and sulfur (d) potassium and iodine. 

Show a Lewis structure for the simplest neutral compound formed from hydrogen and sulfur. 

CASE 3 VALENCE SHELL EXPANSION Lewis diagrams become more complex in compounds formed from elements in the third and subsequent periods. For example, sulfur forms some compounds that are readily described by Lewis diagrams that give closed shells to all atoms. An example is hydrogen snlfide (H2S),... 

The corrosion of metals by non oxidising acids occurs when the metal is able to displace hydrogen ions from the solution. The corrosion effects that arise in the petroleum refining industry are connected with the presence of corrosive sulfur compounds formed by... 

This volume has been divided (arbitrarily) into seven chapters. Chapter 1 contains some interesting syntheses of sulfur- and selenium-containing coordination compounds and clusters including the synthesis of the [Fe4S4(SR)4]2 species which R. H. Holm so elegantly identified as models for active sites in nonheme iron proteins. Compounds formed from S22 and S52 are described. A convenient synthesis of CSe2 is reported. Several additional compounds relevant to biological sulfur chemistry are described. 

Sulfur compounds form the most ubiquitous group of contaminants in fuels (both from fossil and renewable sources) and can affect the process in various manners. Sulfur can be released from the reducer exhaust in the form of SOx and thus... 

Volatile sulfur compounds formed in wine and beer production originate from methionine and are by-products of the microorganism s metabolism. The compounds formed are methional (I), methionol (II) and acetic acid-3-(methylthio)-propyl ester (III, cf. Reaction 5.33). 

The H2S formed can react with the sulfates or rock to form sulfur i (Equation 8.2) that remains in suspension as in the case of crude from Goldsmith, Texas, USA, or that, under the conditions of pressure, temperature I and period of formation of the reservoir, can react with the hydrocarbons to give sulfur compounds ... 

Extraction of Nonmetallic Inorganic Compounds. Phosphoric acid is usually formed from phosphate rock by treatment with sulfuric acid, which forms sparingly soluble calcium sulfate from which the phosphoric acid is readily separated. However, in special circumstances it may be necessary to use hydrochloric acid ... 

Total 1991 world production of sulfur in all forms was 55.6 x 10 t. The largest proportion of this production (41.7%) was obtained by removal of sulfur compounds from petroleum and natural gas (see Sulfurremoval and recovery). Deep mining of elemental sulfur deposits by the Frasch hot water process accounted for 16.9% of world production mining of elemental deposits by other methods accounted for 5.0%. Sulfur was also produced by roasting iron pyrites (17.6%) and as a by-product of the smelting of nonferrous ores (14.0%). The remaining 4.8% was produced from unspecified sources. 

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