> DRAININGS. 109 



die they may readily lose (especially since they are 

 in this situation more powerfully heated by the sun, 

 or in summer-time by the warm atmosphere) the 

 greatest part of their ammonia, that is, their most 

 important manuring constituent, whilst in a. good 

 tank, on the contrary, this loss will be but trifling. 



Third Experiment, — If the hartshorn is boiled in 

 the spoon till the whole liquid is evaporated, the 

 spoon will subsequently appear empty and clean, 

 and exhibit no residue whatever, for the ammonia 

 volatilizes in the heat, and the water also ; hence 

 nothing can be left. Pour now precisely the same 

 quantity of hartshorn into a cup, and drop in cau- 

 tiously, whilst stirring constantly with a wooden 

 spatula, sulphuric acid, until the red test-paper is no 

 longer turned blue by the solution. Should, on the 

 other hand, blue paper be now reddened by the fluid, 

 it is a proof that somewhat too much acid has been 

 added ; and for this reason more hartshorn must be 

 introduced by drops, until the moment arrives in 

 which the liquid produces no change of color in 

 either kind of test-paper. This is called the point of 

 neutralization. The pungent odor of the ammonia 

 has now completely disappeared, and in the same 

 way an acid taste can no longer be remarked. From 

 the sharp caustic fluids, which could not have been 

 brought without injury into contact with the lips, a 

 new body, or salt, has now been produced, which 

 may be tasted without any danger, and possesses 

 a saline taste instead of an acid or alkaline one. 

 10 



