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Some of the hydrogen sulfide will react with metal ions in the water or solid to produce iron or metal sulfides, which are not water-soluble. These metal sulfides, such as iron(II) sulfide, are often black or brown, leading to the color of sludge. Pyrrhotite is a waste product of the Desulfovibrio bacteria, a sulfate reducing bacteria.
In complementary route, iron metal can be oxidized by hydrochloric acid followed by chlorination: [10] Fe + 2 HCl → FeCl 2 + H 2 FeCl 2 + 0.5 Cl 2 + 6 H 2 O → FeCl 3 (H 2 O) 6. A number of variables apply to these processes, including the oxidation of iron by ferric chloride and the hydration of intermediates. [10]
Such solutions are designated "spent acid," or "pickle liquor" especially when the hydrochloric acid is not completely consumed: Fe + 2 HCl → FeCl 2 + H 2. The production of ferric chloride involves the use of ferrous chloride. Ferrous chloride is also a byproduct from the production of titanium, since some titanium ores contain iron. [3]
Metals react with acids to form salts and hydrogen gas. Liberation of hydrogen gas when zinc reacts with hydrochloric acid. + () + [2] [3] However, less reactive metals cannot displace the hydrogen from acids. [3] (They may react with oxidizing acids though.)
However, it does not react with concentrated nitric acid and other oxidizing acids due to the formation of an impervious oxide layer, which can nevertheless react with hydrochloric acid. [11] High-purity iron, called electrolytic iron , is considered to be resistant to rust, due to its oxide layer.
Iron(III) oxide is insoluble in water but dissolves readily in strong acid, e.g., hydrochloric and sulfuric acids. It also dissolves well in solutions of chelating agents such as EDTA and oxalic acid. Heating iron(III) oxides with other metal oxides or carbonates yields materials known as ferrates (ferrate (III)): [18] ZnO + Fe 2 O 3 → Zn(FeO ...
Perls did not publish a detailed procedure other than indicating a dilute potassium ferrocyanide solution was applied to the tissue followed by hydrochloric acid. [2] Ferric iron deposits in tissue (present mostly as ferric iron within the storage protein ferritin) then react with the soluble ferrocyanide in the stain to form the insoluble ...
Nitric acid is a powerful oxidizer, which will dissolve a very small quantity of gold, forming gold(III) ions (Au 3+). The hydrochloric acid provides a ready supply of chloride ions (Cl −), which react with the gold ions to produce tetrachloroaurate(III) anions ([AuCl 4] −), also in solution. The reaction with hydrochloric acid is an ...