Practical physiological chemistry : a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . filter, concentrate the filtrate to asmall volume and allowr it to stand in a cool place. Hypox-anthin should crystallize in small colorless needles. Examinethe crystals under the microscope. 3. Xanthin.—To the filtrate from the above experimentcontaining the xanthin silver nitrate add ammonia in excess.(The crystalline form of xanthin silver nitrate is shown inFig. 80, p. 218.) A brownish-red precipitate of xanthin silverforms. Treat this suspende
Practical physiological chemistry : a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . filter, concentrate the filtrate to asmall volume and allowr it to stand in a cool place. Hypox-anthin should crystallize in small colorless needles. Examinethe crystals under the microscope. 3. Xanthin.—To the filtrate from the above experimentcontaining the xanthin silver nitrate add ammonia in excess.(The crystalline form of xanthin silver nitrate is shown inFig. 80, p. 218.) A brownish-red precipitate of xanthin silverforms. Treat this suspended precipitate with H2S (do notuse an excess of H2S), warm the mixture for a few momentsand filter while hot. Concentrate the filtrate to a small volumeand put away in a cool place for crystallization (Fig. 78, p. 210).To obtain xanthin in crystalline form special precautions are 2l8 PHYSIOLOGICAL CHEMISTRY. generally necessary. Evaporate the solution to the following tests on the crystals or residue: (o) Xanthin Test.—Place about one-half of the crystallineor amorphous material in a small evaporating dish, add a few Fig. Xanthin Silver Nitrate. drops of concentrated nitric acid and evaporate to drynessvery carefully on a water-bath. The yellow residue uponmoistening with caustic potash becomes red in color and uponfurther heating assumes a purplish-red hue. Now add a fewdrops of water and warm. In this way a yellow solution re-sults which yields a red residue upon evaporation. How doesthis differ from the Murexid test upon uric acid ? (b) WeideVs Reaction.—By gently heating bring the re-mainder of the xanthin crystals or residue into solution inbromine-water. Evaporate the solution to dryness on a water-bath. Remove the stopper from an ammonia bottle and byblowing across the mouth of the bottle direct the fumes ofammonia so that they come in contact with the dry these conditions the presence of xanthin is shown bythe residue assuming a red
Size: 1582px × 1579px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherphiladelphiablakis
