Analysis of the Coprolites of Birds. 53 



and made a marginal note in my journal, that probably the por- 

 tion I was then operating upon had been used for testing the 

 presence of sulphuric acid by barytes ; for I found that even 

 water, digested on it, produced a precipitate with sulphuric acid. 

 On reviewing these experiments, and repeating them with your 

 new samples, I find that this precipitate is uric acid, from the 

 urate dissolved even by water. After the action of alcohol, wa- 

 ter gives a perfectly colorless solution, which gave the following 

 characters : 



a. Evaporated, a white earthy crust, which easily chars by 

 heat. 



b. Sulphuric acid produced an immediate milkiness, and in 

 the somewhat concentrated solution, a white precipitate, and as 

 evaporation went on, needles — with all the appearance of sul- 

 phate of lime ; some single, others with the peculiar star-like ag- 

 gregation of that salt, but with those, distinct dots of a white 

 earthy amorphous matter. Exposed to a gentle heat, these last 

 blacken and darken, and then become white. 



c. If the experiment is made with a larger portion of sulphuric 

 acid and water, by careful evaporation, a white earthy, scaly pre- 

 cipitate occurs, but no appearance of needles in the acid liquor 

 as before. This being neutralized by pure ammonia, and then 

 the sulphate of ammonia being sublimed, the earthy precipitate 

 chars without melting or turning white. 



d. The watery solution evaporated dry, with nitric acid turns 

 lemon yellow, and the yellow crust chars by heat. 



e. Nitrate of silver produces a yellow brown precipitate, insol- 

 uble in pure ammonia, which, treated with nitric acid and evap- 

 orated to dryness, gave a pinky salt. 



/. The precipitate by nitrate of silver, at a heat far below red- 

 ness, is immediately decomposed and the silver reduced. What 

 I had before suspected, became now in several trials perfectly 

 distinct. A beautiful film and distinct globules of metallic sil- 

 ver were produced. This silver, &c. were treated with water to 

 remove any nitrate of silver, and the metal again solved in nitric 

 acid, produced all the characters of nitrate of silver. This easy 

 reduction of nitrate of silver is a very distinctive character of 

 uric acid, and forms one of the most exquisite examples of me- 

 tallic reduction with which I am acquainted. 



