<P> In cast iron sulfur promotes the formation of white iron . As little as 0.5% can counteract the effects of slow cooling and a high silicon content (Rostoker & Bronson 1990, p. 21). White cast iron is more brittle, but also harder . It is generally avoided, because it is difficult to work, except in China where high sulfur cast iron, some as high as 0.57%, made with coal and coke, was used to make bells and chimes (Rostoker, Bronson & Dvorak 1984, p. 760). According to Turner (1900, pp. 200), good foundry iron should have less than 0.15% sulfur . In the rest of the world a high sulfur cast iron can be used for making castings, but will make poor wrought iron . </P> <P> There are a number of remedies for sulfur contamination . The first, and the one most used in historic and prehistoric operations, is avoidance . Coal was not used in Europe (unlike China) as a fuel for smelting because it contains sulfur and therefore causes hot short iron . If an ore resulted in hot short metal, ironmasters looked for another ore . When mineral coal was first used in European blast furnaces in 1709 (or perhaps earlier), it was coked . Only with the introduction of hot blast from 1829 was raw coal used . </P> <P> Sulfur can be removed from ores by roasting and washing . Roasting oxidizes sulfur to form sulfur dioxide which either escapes into the atmosphere or can be washed out . In warm climates it is possible to leave pyritic ore out in the rain . The combined action of rain, bacteria, and heat oxidize the sulfides to sulfuric acid and sulfates, which are water - soluble and leached out (Turner 1900, pp. 77). However, historically (at least), iron sulfide (iron pyrite FeS), though a common iron mineral, has not been used as an ore for the production of iron metal . Natural weathering was also used in Sweden . The same process, at geological speed, results in the gossan limonite ores . </P> <P> The importance attached to low sulfur iron is demonstrated by the consistently higher prices paid for the iron of Sweden, Russia, and Spain from the 16th to 18th centuries . Today sulfur is no longer a problem . The modern remedy is the addition of manganese . But, the operator must know how much sulfur is in the iron because at least five times as much manganese must be added to neutralize it . Some historic irons display manganese levels, but most are well below the level needed to neutralize sulfur (Rostoker & Bronson 1990, p. 21). </P>

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