Silver iron secondary

Silver items, however, are also relatively rare in the archaeological record. The most common metal found is either copper, usually alloyed with either tin (bronze) or, in the later periods, zinc (brass), or iron. The latter contains very little lead and, because of severe corrosion problems, its survival rate is often low (but see Degryse et al., 2007). Fortunately, copper can also be characterized from its lead isotope signature, since the primary ore of copper is chalcopyrite (CuFeS2), which often co-occurs with galena (PbS) and sphalerite (ZnS). Even if the ore used is a secondary mineral formed by the oxidation of the primary deposit, the copper smelted from such a deposit would normally be expected to... 

Primary and secondary colors, full intensity Rapt At Rappoport s, 1952 Primary and secondary colors, full intensity The Great Parade, 1954 Low intensity, neutrals Woman Ironing, 1904 Low intensity, neutrals La Place Rauignan, Still Life in Front of an Open Window, 1915 Low intensity, neutrals Chelsea Wharf Grey and Silver, 1875 Full intensity The Gate, 1960 Full intensity, neutrals Artist s Studio, 1974 Light and dark values Le Moulin de la Galette, 1879... 

The purer forms of iron (wrought iron and steel) appear to be much more susceptible to this kind of reaction than cast iron.3 If the attacking acid is readily reducible by hydrogen, many secondary reactions may take place. Thus with nitric acid, oxides of nitrogen and ammonia may be evolved, whilst with selenic acid a deposit of elementary selenium is obtained (see below). When iron is exposed to the action of acids that are also powerful oxidisers—such as, for example, fairly concentrated solutions of nitric and chromic acids,—it is frequently rendered inert or passive.4 Its surface may remain perfectly bright, but the metal does not show any appreciable solution in the acid, and if removed and immersed in dilute solutions of such salts as copper and silver sulphates, no reaction takes place, although ordinary active iron would cause an immediate precipitation of the more electronegative metal. 

---