100 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



chloric acid: precipitate of uric acid (see Quantitative De- 

 termination of Uric Acid, page 188). 



FTG. 8. Uric Acid: (a) from alkali urate by the addition of hydro- 

 chloric acid; (6) spontaneously deposited from urine. 



(6) From Guano or Snake Excrement. Heat to boiling 

 50 g. of finely powdered guano with 500 cc. of water and 100 cc. 

 of caustic soda solution (marked foaming and evolution of 

 ammonia; the experiment is therefore best performed under 

 the hood). Keep boiling for some time, replacing the water 

 which evaporates by hot water, until the greater part of the 

 guano has dissolved, then filter. Pour the filtrate into about 

 300 cc.. of dilute sulphuric acid (20 per cent.) contained in a 

 porcelain dish, and heat to the boiling-point. Continue the 

 heating until the fluid begins to bump and a crystalline sedi- 

 ment precipitates. Examine under the microscope to see 

 that it has no amorphous sodium urate mixed with it. If 

 it has, then more acid must be added and the heating con- 

 tinued with vigorous stirring or on the water-bath. Let cool, 

 filter, wash with water until the filtrate no longer gives a pre- 

 cipitate with barium chloride or only a faint turbidity, drain 

 thoroughly, and dry on filter-paper. 



