Guaiac reaction

The guaiac reaction is a test method that is used to differentiate between species in large mushrooms . So is also Gum arabic checked for its authenticity. The guaiac tincture can also be used to detect blood in urine or stool, a so-called haemoccult test . In general, oxidizing agents are detected in the sample with the reaction .

The guaiac tincture or solution is made by dissolving a few crystals of guaiac resin in 2-3 ml of 60-70% ethanol.

Use to identify fungi

The solution is dripped onto the stem of the mushroom below the lamellae. If the reaction is positive, the stalk flesh turns bluish or bluish-green. The reaction can be quick or slow, or weak, normal, or very intense.

The ability to stain with guaiac solution is an important determinant , especially for deaflings .

reaction

In the presence of dilute hydrogen peroxide solution contained in the resin is guaiaconic (also Furoguajacin) to Guajakblau oxidized . Guaiac blue consists of various colored compounds of the furoguajacin blue type.

The Pagenstecher-Schönbei cyanide sample is also based on the formation of guaiac blue. The acidified sample material is placed in a flask on a test paper that has previously been soaked with guaiac tincture and copper sulfate solution. Hydrocyanic acid is formed in the closed vessel , which converts to copper (II) cyanide with the copper sulfate . This in turn forms (with reduction to copper (I) cyanide ) with the guaiaconic acid of the resin guaiac blue.

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• Russulas. (DOC) Micologia.biz Web de micología Europea, p. 20 , accessed June 20, 2011 (Spanish). 

• Ewald Gerhart (Ed.): Mushrooms Volume 1: Lamellar mushrooms, deafblings, milklings and other groups with lamellas . BLV Verlagsgesellschaft, Munich / Vienna / Zurich 1984, ISBN 3-405-12927-3 , p. 276 .