Sulfite process

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. 

Paper Products. Paper (qv) products account for about 2% of sulfur demand. The largest single segment of demand is in the manufacture of wood pulp by the sulfite process (see Pulp). In this process, the main sulfur intermediate is sulfur dioxide, which is generally produced at the plant site by burning elemental sulfur. Some sulfur dioxide, however, is produced as a by-product at smelter operations, purified andUquefied, and shipped to the pulp mills. The sulfur dioxide is converted to sulfurous acid, and the salt of this acid is a principal component of the cooking Hquor for the sulfite process. 

Sulfur dioxide Fuel combustion (coal, oil), smelting and casting, manufacture of paper by sulfite process Primary metals (ferrous and nonferrous) pulp and paper Sensory and respiratory irritation, vegetation damage, corrosion, possible adverse effect on health... 

Laugemittel, n. leaching agent, laugen, .t. lye, steep in l.ye buck leach, lixiviate. — gelaugte Saure, (Paper) tower liquor to which has been added liquor from the cookers (in the sulfite process). 

Highly bleached and purified sulfite process wood pulp suitable for conversion into products such as rayon, viscose, acetate, and cellophane... 

Sulfite process wood pulp with or without bleaching used for products such as tissue papers, fine papers, and newsprint... 

Sulfite pulps have less color than kraft pulps and can be bleached more easily however, they are not as strong. The efficiency and effectiveness of the sulfite process is also dependent on the type of wood furnish and the absence of bark. For these reasons, the use of sulfite pulping has declined in comparison to kraft pulping over time. 

Attisholz A process for recovering valuable waste products from the sulfite process for making wood pulp. This includes methanol, cymenes, and furfural. Developed in Switzerland. 

SCA-Billerud A variation of the sulfite process for making paper from wood, in which the waste hydrogen sulfide is burnt to sulfur dioxide and used to make sulfuric acid. 

Acid soak cleaners, for electroplating, 9 783 Acid soap, 22 728 Acid soluble dyes, 7 373t Acid solutions hydrazine, 13 587 in leaching chemistry, 16 152 Acid sulfite process, 23 540-541 Acid sulfite pulping, 21 22-23, 26 Acid treatment, in petroleum refining,... 

Figure 3.10 Relative amounts of lignin and carbohydrate removed during the Kraft and acid sulfite processes.

Figure 5.2 Environmental scanning electron photomicrographs of fibres of a chemically pulped (sulfite process) softwood (a) before refining and (b) after refining.

Chemical pulping of wood is commonly carried out according to the Kraft (sulfate) or sulfite processes [13]. These methods are described in the following subsections. 

Writing paper was first used in Egypt as far back as 2500-2000 BC, made from the papyrus reed. Paper manufacture began in China about AD 105. In 1690 the first American paper mill began its operation. Two recent dates of importance to modem paper technology are 1867, when Tilghman in the U.S. developed the sulfite process, and 1884, when Dahl in Germany discovered the kraft or sulfate process. 

VIII. Hydrolysis of Wood During Sulfite Process I ulping. 186... 

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