Xanthydrol test

Filthy conditions, due to rodent or insect population, may be observed in a grain warehouse. The inspector notes rat-chewed flour sacks and sacks contaminated with rat excrement. He removes a sample of sacking and flour from such contaminated areas and submits them to the analyst. Urine fluoresces under ultraviolet light. Where rodent urine is to be confirmed, the xanthydrol test is one of several that may be used. Excreta pellets may be moistened with water or an appropriate clearing solution and crushed for observation under the compound microscope. The presence of striated hair fragments indicates rodent excrement. 

Xanthydrol test. Dissolve the compound in 50% acetic add and add to the solution 1 ml of 5 % methanolic xanthydrol reagent. An immediate predpitate of the xanthyl derivative is given by urea, urea salts and mono-substituted ureas. After recrystallization from aqueous dioxan, the product can be retained as a derivative. 

The following reactions were used for the industrially important benzene hexachloride with zinc or, better, magnesium, in glacial acetic acid, benzene hexachloride is dechlorinated to benzene, which can then be detected by the Janovsky or Mohler color reaction (p. 356) (18—20). Also, the test proposed for DDT, i.e., nitration and the reaction of the nitro compoimds formed with methanolic sodium hydroxide, is recommended (21). Other tests recommended are the reaction of DDT with sulfuric acid in acetic acid (22), the reaction with xanthydrol, alkali, and pyridine (23), and the reaction with benzene according to the Friedel-Crafts procedure (24). 

Procedure Formamide (70 mg) is mixed in a 5-ml micro test tube with 2 ml of a 5% xanthydrol solution in glacial acetic acid and the tube is immersed in a water bath at 80 °C for 20 min. It is then allowed to cool in a refrigerator for 20 min and the product separated is filtered under suction on a filtration tube. Yield, 0.13 g mp, 184—187 °C. After crystallization from 4 ml of 70% dioxane the product (0.10 g) melted at 183 to 185 °C. If the product does not separate after prolonged standing in the refrigerator, the mixture should be diluted with a few drops of water. 

Owing to its low solubility, the xanthydrol is used as a 10 per cent, solution in methyl alcohol, and the urea solution must contain a large excess of glacial acid to keep the free xanthydrol from being precipitated by water, and also to unmask the amido groups so that they will react. The test will reveal urea in concentrations of 1 10,000 in about fifteen seconds and 1 800,000 in ten minutes. A positive result is shown by a crj talline precipitate of di-xanthylurea slowly appearing as a cloud of fine, colourless, silky needles. 

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