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Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining with the increasing recognition of the toxicity of arsenic and its compounds. [15] Arsenic has been known since ancient times to be poisonous to humans. [16]
Any arsenic present would appear as arsenic trioxide and then could be subjected to Metzger's test. The most common test (and used even today in water test kits) was discovered by Samuel Hahnemann . It would involve combining a sample fluid with hydrogen sulfide (H 2 S) in the presence of hydrochloric acid (HCl).
In its standard state arsine is a colorless, denser-than-air gas that is slightly soluble in water (2% at 20 °C) [1] and in many organic solvents as well. [citation needed] Arsine itself is odorless, [5] but it oxidizes in air and this creates a slight garlic or fish-like scent when the compound is present above 0.5 ppm. [6]
The earliest gold artifacts were discovered at the site of Wadi Qana in the Levant. [13] Silver is estimated to have been discovered in Asia Minor shortly after copper and gold. [14] There is evidence that iron was known from before 5000 BC. [15] The oldest known iron objects used by humans are some beads of meteoric iron, made in Egypt in ...
The Lower Paleolithic period lasted over 3 million years, during which there many human-like species evolved including toward the end of this period, Homo sapiens.The original divergence between humans and chimpanzees occurred 13 (), however interbreeding continued until as recently as 4 Ma, with the first species clearly belonging to the human (and not chimpanzee) lineage being ...
An image from John Dalton's A New System of Chemical Philosophy, the first modern explanation of atomic theory.. This timeline of chemistry lists important works, discoveries, ideas, inventions, and experiments that significantly changed humanity's understanding of the modern science known as chemistry, defined as the scientific study of the composition of matter and of its interactions.
The history of astronomy focuses on the contributions civilizations have made to further their understanding of the universe beyond earth's atmosphere. [1] Astronomy is one of the oldest natural sciences , achieving a high level of success in the second half of the first millennium.
First human-piloted space flight (Alan Shepard). First human-crewed suborbital flight. USA Freedom 7: 19 May 1961: First planetary flyby (within 100,000 km of Venus – no data returned). USSR Venera 1: 6 August 1961: First crewed space flight lasting over twenty four hours by Gherman Titov, who is also the first to suffer from space sickness ...