358 



PEACTICAL PHYSIOLOGY 



colour persists, thus differing from the murexide stain which, when similarly 

 treated, loses its colour (see p. 425). 



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 so as to remove 

 the silver which it contains : the silver sulphide is filtered off, and the filtrate 



FIG. 234. Hypoxanthin silver nitrate. x300. 



FIG. 235. Zinc sarcolactate. X300. 



evaporated till all the ammonia has been expelled. It is then made strongly acid 

 with phosphoric acid, and the lactic acid, which is hereby liberated, is dissolved 

 out by shaking it in a separating funnel with ether. 



After extracting three or four times, the ethereal extracts are combined and 

 the ether evaporated away by placing on a water bath heated to about 60 C., the 

 flame underneath which has been extinguished. An acid syrup remains behind ; 

 this is impure lactic acid. In order to purify it, dilute three times with water, 

 bring the resulting solution to the boil, and then carefully add powdered zinc 

 carbonate until the reaction is neutral. Filter. Evaporate the filtrate to small 

 bulk, and add an equal bulk of spirit and allow to stand, when zinc sarcolactate 



