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Usually it is done by passing hydrogen sulfide over the test tube for detection of 1st group cations. If it forms a reddish-brown or black precipitate then Bi 3+ , Cu 2+ , Hg 2+ or Pb 2+ is present. Otherwise, if it forms a yellow precipitate, then Cd 2+ or Sn 4+ is present; or if it forms a brown precipitate, then Sn 2+ must be present; or if ...
Devarda's alloy (Copper/Aluminium/Zinc) is a reducing agent.When reacted with nitrate in sodium hydroxide solution, ammonia is liberated. The ammonia formed may be detected by its characteristic odor, and by damp red litmus paper's turning blue, signalling that it is an alkali — very few gases other than ammonia evolved from wet chemistry are alkaline.
Most people who take a drug test take a presumptive test, cheaper and faster than other methods of testing. However, it is less accurate and can render false results. The FDA recommends for confirmatory testing to be conducted and the placing of a warning label on the presumptive drug test: "This assay provides only a preliminary result.
Capillary electrophoresis (CE) is a family of electrokinetic separation methods performed in submillimeter diameter capillaries and in micro- and nanofluidic channels.Very often, CE refers to capillary zone electrophoresis (CZE), but other electrophoretic techniques including capillary gel electrophoresis (CGE), capillary isoelectric focusing (CIEF), capillary isotachophoresis and micellar ...
It is important to note that thorough documentation of the scene through notes, photographs etc. must be done prior to any presumptive or confirmatory testing in order to maintain chain of custody and avoid contamination. The Griess test and Walker test are two presumptive tests that can be used to determine if a questioned sample contains ...
In chemistry, a chemical test is qualitative or semi-quantitative procedure designed to prove the existence of a chemical compound or chemical group with the aid of a specific reagent. Subcategories This category has the following 3 subcategories, out of 3 total.
Tollens' test for aldehyde: left side positive (silver mirror), right side negative Ball-and-stick model of the diamminesilver(I) complex. Tollens' reagent (chemical formula ()) is a chemical reagent used to distinguish between aldehydes and ketones along with some alpha-hydroxy ketones which can tautomerize into aldehydes.
A range of qualitative and quantitative tests have been developed to detect phosphate ions (PO 3− 4) in solution. Such tests find use in industrial processes, scientific research, and environmental water monitoring.