236 GUANO. 



After addition of excess of hydrochloric acid, it 

 gives, with chloride of barium, a considerable precipi- 

 tate of sulphate of baryta. 



X. When guano is exahusted with cold water, and 

 the residue digested with a weak solution of caustic 

 soda, uric acid is extracted. The solution is filtered, 

 and feebly acidulated with hydrochloric acid, when 

 the uric acid is precipitated. After being filtered off 

 and washed, it is easily soluble in caustic potassa, and 

 may be reprecipitated by hydrochloric acid. If it be 

 dissolved in warm dilute nitric acid, the solution evapo- 

 rated to dryness, and the residue moistened with 

 carbonate of ammonia, a fine purple-red color is pro- 

 duced. 



XI. The quantity of organic matter can be estimated 

 directly only by an ultimate organic analysis. In 

 good undried guano it amounts, taking the ammonia 

 into account, to about 50 per cent. 



XII. The exact determination of the nitrogen re- 

 quires also an ultimate analysis. This element should 

 amount to 12 or 14 per cent.; bad samples contain 

 only from 1 to 6 per cent. The quantity of nitrogen, 

 may, however, be approximately determined by the 

 following method, which therefore allows us to ascer- 

 tain rapidly the value of different specimens of guano. 

 It depends upon the circumstance that when guano is 

 treated with a solution of chloride of lime(hypochlorite 

 of lime), the nitrogen of the organic matter and of the 

 ammoniacal salts is evolved as gas.* Instead of col- 

 lecting and measuring the gas evolved, which would 

 be scarcely practicable, on account of the violent effer- 

 vescence, the volume of water which is expelled by 

 the gas is ascertained by means of the simple apparatus 



* Farther experiments are required to show that all the nitrogen 

 is here evolved in the gaseous state, and to ascertain how the 

 various nitrogen-compounds behave with chloride of lime. 



