ANALYTICAL EVIDENCE. 



821 



An excellent method of detecting the presence of cystic 

 oxide in calculi or gravel is the following : 



The calculus is dissolved in a strons; solution of caustic 

 potash, and to the solution is added so much of a solution 

 of acetate of lead, that all the oxide of lead is retained in 

 solution. When this mixture is boiled there is formed a 

 black precipitate ^of sulphuret of lead, which gives to the 

 liquid the aspect of ink. Abundance of ammonia is also 

 disengaged ; and the alkaline fluid is found to contain, 

 among other products, oxalic acid. 



NOTE (33), p. 137. 



COMPOSITION OF OXALIC, OXALURIC, AND PARABA- 



NIC ACIDS. 



1. Oxalic Acid (hydrated). 



Gay Lussac &. Thc^nard. Berthollet. q.-, 03 + H O 



Carbon 26-566 25'13 26-66 



Hydrogen ... 2-745 3-09 2'22 



Oxygen 70-689 71*78 71*12 



2. OxALTjRic Acid, a 



WOhleran d Liebig.> c^H^Nfos 



Carbon 27'600 27*318 27*59 



Hydrogen 3*122 3*072 3*00 



Nitrogen 21*218 21*218 21*29 



Oxygen 48*060 48*392 48*12 



a Ann. der Pharin., XXVI., 289. 



3. Parabanic Acid, a 



Wohler and Liebig.* 



Carbon 31*95 31*940 31*91 



Hydrogen 2*09 1*876 1*73 



Nitrogen 24*66 24*650 24*62 



Oxygen 41*30 41*534 41*74 



a Ann. clex- Pharm., XXVI., 286. 

 Y 



