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A drained pond, showing the layer of sludge on the bottom; its black colour is due to the presence of metal sulfides, the result of reactions with hydrogen sulfide produced by bacteria. Hydrogen sulfide is a central participant in the sulfur cycle, the biogeochemical cycle of sulfur on Earth. [112]
An example of histotoxic hypoxia is cyanide poisoning. There is a profound drop in tissue oxygen consumption since the reaction of oxygen with cytochrome oxidase is blocked by the presence of cyanide. Cyanide binds to the ferric ion on cytochrome oxidase a 3 and prevents the fourth and final reaction in the electron transport chain.
Treatment of sulfur with hydrogen gives hydrogen sulfide.When dissolved in water, hydrogen sulfide is mildly acidic: [5] H 2 S ⇌ HS − + H +. Hydrogen sulfide gas and the hydrosulfide anion are extremely toxic to mammals, due to their inhibition of the oxygen-carrying capacity of hemoglobin and certain cytochromes in a manner analogous to cyanide and azide.
In aqueous solution, it has a corresponding pK a value of 6.9. Its conjugate acid is hydrogen sulfide (H 2 S). However, bisulfide's basicity stems from its behavior as an Arrhenius base. A solution containing spectator-only counter ions, has a basic pH according to the following acid-base reaction:
Sulfur medications such as phenacetin, metoclopramide, dapsone, phenzopyridine, and trimethoprim-sulfamethoxazole; hydrogen-sulfide-producing intestinal bacteria, such as Morganella morganii: Risk factors: Pulmonary arteriovenous malformation: Prevention: Avoidance of sulfur-containing compounds including drugs: Treatment: Blood transfusions
While the determination of the specific toxin can be time-consuming due to the number of different substances that can cause injury or death, certain clues can narrow down the possibilities. For example, carbon monoxide poisoning would result in bright red blood while death from hydrogen sulfide poisoning would cause the brain to have a green hue.
To reduce the extra sulfur in the ruminant's diet, ruminal bacteria break the excess down, resulting in Hydrogen Sulfide, which is soluble in water, but as temperature increases, the solubility decreases, which leads to the hydrogen sulfide gas being reinhaled by the animal, causing sulfur induced polioencephalomalacia.
In 1832, a certain John Bodle was brought to trial for poisoning his grandfather by putting arsenic in his coffee. James Marsh, a chemist working at the Royal Arsenal in Woolwich, was called by the prosecution to try to detect its presence. He performed the standard test by passing hydrogen sulfide through the suspect fluid.