URINARY CALCULI. 95 



portion of the original calculus, 'dissolve in concen- 

 trated nitric acid, evaporate to dryness on a water bath 

 in a white porcelain evaporating dish ; dip a glass rod 

 into the strongest ammonia, and bring it near the 

 residue in the dish, and observe whether a pink colour 

 is produced or not. 



I. A pink colour is produced, proving that the cal- 

 culus contains uric add; observe whether a 

 portion of the calculus melts on being heated. 



a. It melts 



1. And communicates a strong yellow colour 

 to the flame of a spirit lamp or Bunsen 

 burner ; Sodium urate. 



2. And communicates a violet colour to the 

 flame, giving the potassium spectrum ; Potas- 

 sium urate. 



b. It does not melt; dissolve the residue left after 

 ignition in a little dilute hydrochloric acid, add 

 ammonia till alkaline, and then ammonium 

 carbonate solution. 



1. A white precipitate falls ; Calcium urate. 



2. No precipitate; add some hydric sodic 

 phosphate solution ; a white crystalline pre- 

 cipitate falls ; Magnesium urate. 



II. No pink colour is produced. Observe whether a 

 portion of the calculus melts on being heated 

 strongly. 



a* It melts (fusible calculus). Treat the residue 

 with acetic acid : it dissolves ; add to the 



