A laboratory manual of physiological and pathological chemistryFor students in medicine . cooling. The addition of the urea isto prevent the formation of nitrous acid, which might decom-pose the xanthine bases. Filter the hypoxanthine silvernitrate off after a few hours and wash unti! the wash-waterno longer reacts strongly acid. Let the filtrate (without thewash-water) stand till next day and filter (without workingup the precipitate, which is a mixture of hypoxanthine silvernitrate and xanthine silver nitrate). The filtrate is used toshow the presence of xanthine. The hypoxanthine silvernitr
A laboratory manual of physiological and pathological chemistryFor students in medicine . cooling. The addition of the urea isto prevent the formation of nitrous acid, which might decom-pose the xanthine bases. Filter the hypoxanthine silvernitrate off after a few hours and wash unti! the wash-waterno longer reacts strongly acid. Let the filtrate (without thewash-water) stand till next day and filter (without workingup the precipitate, which is a mixture of hypoxanthine silvernitrate and xanthine silver nitrate). The filtrate is used toshow the presence of xanthine. The hypoxanthine silvernitrate is examined under the microscope (fine needles fre-quently grouped in the form of stars). 26 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. Conversion of the Hypoxanthine Silver Nitrate intoHypoxanthine. (a) By Means of Hydrochloric Acid. Pierce the filter andwash the precipitate into a flask. Add a few cubic centi-meters of hydrochloric acid, shake thoroughly and continu-ously, and finally warm gently. The hydrochloric acid de-composes the silver compound with the separation of silver. Fig. 1.—Hypoxanthine Silver Nitrate, chloride. By thoroughly shaking and gently warming thissettles well. The completion of the decomposition is con-trolled by a microscopical examination. Heating too stronglyis to be avoided, aB otherwise the aqua regia formed maydestroy the hypoxanthine.^ When the decomposition is com-plete, filter, make the filtrate alkaline with ammonia, andevaporate to dryness on the water-bath. Treat the residuewith a small quantity of water, which dissolves the ammo-nium chloride and nitrate formed, but leaves the hypoxan-thine undissolved. ^ In order to avoid this it is advisable first to convert the hypoxan-thine silver nitrate into the hypoxanthine silver compound (see below). EXAMINATION OF MUSCULAR TISSUE. 27 (b) By Means of Hydrogen Sulphide. Put the hypoxanthine silvernitrate into a flask with some water and pass in hydrogen sulphide,shaking frequenth, untH the pr
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