Color reaction

About: Color reaction is a research topic. Over the lifetime, 1194 publications have been published within this topic receiving 19579 citations.

A critical investigation of the liebermann colour test: The formation and behaviour of phenolindophenol in strong acid media

Abstract: The Liebermann test has been investigated by spectroscopic and Chromatographic methods Phenols in concentrated sulphuric acid reacted with nitrite to give green to blue solutions which turned to red or violet, yellow or brown, respectively, after dilution with water Alkalization of these solutions changed the colour to green or blue, but also to yellow or brown, respectively The reaction of phenols withp-nitrosophenol was also studied Except for 4-iodophenol and hydroquinone, phenols substituted in thep-position did not react with either nitrite orp-nitrosophenol Negative reactions were obtained with 2- and 3-nitrophenols, 2- and 3-hydroxybenzoic acids and 2,6-dichlorophenol, although these phenols have a freep-position The sensitivity is much poorer than that of other reactions for detection of phenols, eg the Emerson or Gibbs reactions The Liebermann test is often recommended as a generic test for phenols, but its importance, selectivity and sensitivity seem to have been considerably overestimated Application of the reaction for spectrophotometric determination of phenols is impracticable, because of the very poor reproducibility, the small yield of reaction product and the inconvenience of working with concentrated sulphuric acid mediap-Nitrosophenol was found to be the operative species and the main product was phenolindophenol, which is present in its diprotonated form H2In2+ in the medium of concentrated sulphuric acid Further forms of the dye can exist, depending on the pH or Ho of the medium The orange spiro(7-hydroxyacridine-9,1′-cyclohexa-2′,5′-dien)-2,4′-dione was found to be the main byproduct of the reaction The formation of further by-products was observed, of which 1,4-benzoquinone and 4-nitrophenol were identified

An azo colour reaction for the determination of vitamin B1 in national flour

Abstract: Kuhn, R., Wagner-Jauregg, T., Klaverin, F. H. & Vetter, H. [19351. Hoppe-Seyl. Z. 234, 196. Loofbourow, J. R. & Harris, R. S. [1942]. Cereal Chem. 19, 151. Ministry of Food [1942]. Natitre, Lond., 150, 538. Mukherji, A. [1939]. J. Indian chem. Soc. 16, 273. Nicholls, J. R., Booth, R. G., Kent Jones, D. W. & Ward, H. H. [1942]. Analyst, 67, 15. Peters, R. A. [1935]. Nature, Lond., 135, 107. Pyke, M. [1939]. J. Soc. chem. Ind., dLond., 58, 338. Research Association of British Flour-Millers [1942]. Nature, Lond., 149, 460. Ritsert, K. [1938]. Dtsch. med. Wschr. 64, 481. Todd, A. R., Bergel, F., Fraenkel-Conrat, H. L. & Jacob, A. [1936]. J. chem Soc. p. 1601. Wang, Y. L. & Harris, L. J. [1942]. Chem. Ind. 61, 27. Westenbrink, H. G. K. & Goudsmit, J. [1938]. Enzymologia, 5, 307. & Jansen, B. C. P. [1938]. Acta brev. neerl. Phy8iol. 8, 119.

Composite reagent kit for checking textile formaldehyde content

Abstract: The invention discloses a composite reagent case that is used for detecting formaldehyde content of fabrics, which comprises a composite reagent A, a composite reagent B, a nano titanium dioxide reagent and a standard matching sample; wherein, the composite reagent A is prepared by evenly mixing a commercial 0.1 percent butyl phthalate and a commercial 2 percent sodium sulfite according to the weight ratio between 1 to 1 and 1 to 4; the composite reagent B is prepared by evenly mixing a 0.5 to 2 percent phenethyl alcohol solution and a 0.1 to 0.5 percent sulfuric acid solution according to the weight ratio of 1 to 1; the standard matching sample is a color reaction solution group with standard formaldehyde content or a color comparison card. The composite reagent case has convenient use and fast detection, can obtain final reaction solutions with different colors according to the formaldehyde with different densities, can easily distinguish the formaldehyde content in test samples, and has simple and fast operations as well as accurate and reliable results.