ADVANCED PHYSIOLOGICAL CHEMISTRY 



443 



will be obtained. To separate the xanthin this precipitate is treated in 

 exactly the same way as for hypoxanthin. 



Test for Hypoxanthin. Place a piece of hypoxanthin in a small 

 evaporating dish with a few drops of concentrated pure nitric acid and 

 evaporate slowly to dryness : a brilliant yellow residue is obtained. 



FIG. 270. FIG. 27L 



FIG. 270. Hypoxanthin silver nitrate, x 300. 

 FIG. 271. Zinc sarcolactate. x 300. 



Cool, and then add a drop of sodium hydrate solution, when the residue 

 will change to orange. If the residue be dissolved in water and the 

 solution again evaporated to dryness the orange colour persists, thus 

 differing from the murexide stain which, when similarly treated, loses 

 its colour (see p. 258). 



Test for Xanthin. Repeat the same test as for hypoxanthin and 

 note that the sodium hydrate produces in this case a deep red colour, 

 which persists on dissolving in water and evaporating. 



Sarcolactic Acid. The ammoniacal filtrate, from which the alloxuric 

 bodies have been separated, is treated with sulphuretted hydrogen gas 



