- A substance used to produce a chemical reaction to detect, measure, produce, etc. other substances.
* * *Any substance added to a solution of another substance to participate in a chemical reaction. [Mod. L. reagens]- Benedict-Hopkins-Cole r. magnesium glyoxalate, made from a mixture of oxalic acid and magnesium, used for testing proteins for the presence of tryptophan.- diazo r. two solutions, one of sodium nitrite, the other of acidified sulfanilic acid, used in bringing about diazotization. SYN: Ehrlich diazo r..- Drabkin r. a solution used in the cyanmethemoglobin method of measuring hemoglobin. It consists of sodium bicarbonate, potassium cyanide, and potassium ferricyanide.- Ehrlich diazo r. SYN: diazo r..- Esbach r. picric acid, citric acid, and water (in the proportions 1, 2, and 97) used for the detection of albumin in the urine.- Exton r. 50 g of sulfosalicylic acid and 200 g of Na2SO4 10H2O in a liter of water, used as a test for albumin.- Fouchet r. a 25% solution of trichloroacetic acid, containing 0.9% ferric chloride; a drop of the r. added at the surface line of barium chloride-impregnated filter paper that has been dipped in urine for 10 s will give a green color if bilirubin is present. SEE ALSO: Fouchet stain.- Froehde r. sodium molybdate in strong sulfuric acid; this r. gives various color reactions with alkaloids.- Frohn r. bismuth subnitrate (1.5) and water (20.0) heated to boiling, to which hydrochloric acid (10.0) and potassium iodide (7.0) are added; used to test for alkaloids and for sugar.- Girard r. the hydrazine of betaine chloride, used to extract ketonic steroids by forming water-soluble hydrazones with them.- Hahn oxine r. an alcoholic solution of 8-hydroxyquinoline used in the determination of zinc, aluminum, magnesium, and other minerals.- Hammarsten r. a mixture of 1 part 25% solution of nitric acid and 19 parts 25% solution of hydrochloric acid; the addition of a few drops to a mixture of 1 part of this r. and 4 parts alcohol will give a green color if bile is present.- Ilosvay r. sulfanilic acid 0.5, dissolved in dilute acetic acid 150, mixed with naphthylamine 1, and dissolved in boiling water 20; the blue sediment that forms is dissolved in dilute acetic acid 150; a few drops of this r. added to water, saliva, or other fluid to be tested will produce a red color if nitrites are present.- Kasten fluorescent Schiff reagents fluorescent analogs of Schiff r. that are fluorescent basic dyes lacking acidic side groups and containing one or more primary amine groups; used in cytochemical detection of DNA in Kasten fluorescent Feulgen stain, polysaccharides in Kasten fluorescent PAS stain, and proteins in the ninhydrin-Schiff stain; such analogs include acriflavine, auramine O, and flavophosphine N.- Meyer r. a solution of phenolphthalein with sodium hydroxide, in water (glass-distilled); in the presence of minute traces of blood, the solution becomes purple or blue-red.- Nessler r. a solution of potassium hydroxide, mercuric iodide, and potassium iodide; it yields a yellow color with ammonia (a brown precipitate with larger amounts) that can be used for quantitative assay.- Rosenthaler-Turk r. a solution of potassium arsenate in sulfuric acid used in obtaining color tests for various opium alkaloids.- Schaer r. an alcoholic or aqueous solution of chloral hydrate used as an extraction medium in investigations of alkaloids.- Schiff r. an aqueous solution of basic fuchsin or pararosaniline that is decolorized by sulfur dioxide, commonly prepared by addition of hydrochloric acid to a dye solution containing a metabisulphite or bisulphite salt; used for aldehydes and in histochemistry to detect polysaccharides, DNA, and proteins. See Feulgen stain, periodic acid -Schiff stain, ninhydrin-Schiff stain for proteins.- Scott-Wilson r. an alkaline solution of mercuric cyanide and silver nitrate used in the detection of acetone.- Sulkowitch r. a r. for the detection of calcium in the urine, consisting of 2.5 g of oxalic acid, 2.5 g of ammonium oxalate, 5 mL of glacial acetic acid, and distilled water to make 150 mL; a milky precipitate of calcium oxalate is formed when the r. is added to urine that contains calcium.- Uffelmann r. a solution prepared by adding a 2% solution of phenol in water to aqueous ferric chloride until the solution becomes violet in color; this turns lemon yellow in the presence of lactic acid, assumes an opaline tint in butyric acid, and is decolorized by hydrochloric acid.- Wurster r. filter paper impregnated with tetramethyl-p-phenylenediamine, which turns blue in the presence of ozone or hydrogen peroxide.
* * *re·agent rē-'ā-jənt n1) a substance used (as in detecting or measuring a component, in preparing a product, or in developing photographs) because of its chemical or biological activity2) REACTOR (1b)
* * *re·a·gent (re-aґjənt) [re- + agent] a substance employed to produce a chemical reaction so as to detect, measure, produce, etc., other substances.
Medical dictionary. 2011.